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TABTE OF CONTENTS CHAPTER- 1 THE HIGHWAY AND ITS DEVELOPMENT
1-1 Brief History
of Roads
l-2 Early Laws that Regulates Roadway l-3 Highways in the Philippines 14 Planning Difficulties l-5 Highway Programming l-6 The Planner l-7 Community Involvement l-8 Highway Eeonorny l-9 Computation and Survey 1-10 Remote Sensing 1-l I Photogrammetic Mapping 1-12 Orthophotographs l-13 Colored Photographs 1-14 Locatron ofthe Proposed Highway l-15 Location of Bridges l-16 Highway Plans and Specifications
I 2 3
4 6 8
9 9
ll l3 t3 l5 15
16
2-2 Definition of 2-3 The Design Speed
24 Cross Section of Typical Highways 2-5
2-6
Road Shoulder Cross Slope Cut or Fill Slope
'T-he
2-7 2-8 Number of Lanes 2-9 Highway Median 2-10 The Grade Line 2-l I Vertical Curve Over Crest 2-12 Right ofWay 2-13 Stopping Sight Distance 2-14 T1rre ing Siglrt Distance 2-15 Road Alignment 2-16 Circular Curves
63
65 65 68 72
76 78 78
CHAPTER- 3 SOIL
3-I
Soil and its
Origin
79
il
3-3 Characteristics of Soil 3-4 Classification for Soils 3-5 Composition of Soil 3-6 Soil Reaction to Density 3-7 In-Piace Density and Unit Weight 3-8 R.elative Density
84 89
107
I02 103
T7
t9
CNAPTER-2 DNG THE HICHWAY
2-l Consistency
2-17 Super Elevation-Runoff 2-18 Widening of Curves 2-19 Island 2-20 Types of lnterchange 2-21 Highway Intersection at Grade 2-22 Freeway Entrance and Exit 2-23 Railroad- Highway Separation 2-24 Bicycle l-ane
23 23 27
29 34 42 43
46 46 53 55
56 57 59 60
6l
CHAPTER- 4 SOIL TEST AND SURVEY
4-I Test for Farticle Size 4-Z Test to Evaluate the Effect of Moisture 4-3 Density Test of Soil 44 Laboratory Test for Soil Density 4-5 Field Density Test of Soil in Place 4-6 The Strength Test 4-7 Soil Survey
106
r07 110 111 113
ll4 t20
CHAPTER- 5 ROAD MATERIALS
5-1
Aggregates
5:2 Aggreg:ile for Bituminous Pavernent 5-3 Aggregate for Portland Cement Concrete
Pavement 5-4 Mineral Filler 5-5 Bituminous Material 5-6 Bituminous Binders 5-7
Problems Associated with Bituminous
123 128 129 132 133 135
Binders
139
5-8 5-9
Bituminous Pavement Asphalt Concrete Pavement 5-10 Bituminous Pavement Failure 5-l Macadam Asphalt Mat
I
139
t4l t4r
142
5-12 Surface Treatnent 143 5-13 Aggregate for Bituminous Concrete 148 5-14 DPWH Standard Specifications on Prime Coat Tack Coat and Seal Coat t54 5-15 Geoplastic Fabrics t67
7-9 Construction of Fills and Embankment 0 Sub-Grade Preparation
7-l
7-l
I
8-l 8-Z 8-4 8-5
6-l
Drainage
t69 t7a
6-2 Hydrology
64
Drainingthe Highway
6-5 Manhole, lnlets and Catch Basin 6-6 Channel 6-7 Culvert 6-8 Design of Underdrain 6-9 Debris Control 6-10 The Legal Aspect of Drainage 6-11 Roadway Design and Construotion for 6-12 6-13 6-14 6-15
Unusual Soil Conditions Stabilizing the Unsupporred Slope Improving the Stability of Slope Retaining Wall
Highway Bridges
172
t75 t77 t79 190
r92 193
193
r97 201
204
2t5
CHAPTER- 7 CONSTRUCTING THE ROADBf,I)
7-I 7-Z 7-3 7-4 7-5
Soil as Sfucture Types of Base Course Treated Base Course Grading and Maintenance of Untreated Surface PWH Standard Specifications on Aggregate Sub-Base Course Clearing and Grubbing
7-6 7-7 Excavation 7-8 Free Haul -
227
23s 237
Overhaul (Item 107)
8-6 8-7 8-8
Portland Cement Concrete Pavement Characteristics and Behavior Control of Cracks Transverse Expansion ts Longitudinal ts Construction t Reinforcement of ts The Sub-Grade and Sub-Base for Concrete
244
253
254 257 257 259
260 261
Pavement 262 Proportions 263 Mixture 265 8-l I Polymer Concrete 267 8-12 Curing of Concrste Pavement 267 8-13 DPWH Specifications on Concrete Pavement 268 8-14 Equipment 274 8-15 Preparation of Grade 276 8-9
Concrete 8-10 Concrete
8-16 Flandling Measuring and Batching of Materials 8-17 Placing or Depositing of Concrete 8-18 Finat Consolidation and Finishing 8-19 Curing 8-20 Removal of Forms 8-21 Concreting bythe Slip Form Method 8-22 Tolerance and Pavement Thickness
2t9 22A 222 225
248 248
CHAPTER- 8 CONCRETE PAVEMENT
8-3
CHAPTER{ DRAINAGE AND SLOPE PROTECTION
Compaction and Stabilization
241
CHAPTER_
278 280
285 291 293 293
296
9 ROAD MAINTENANCE
maintenance management Rehabilitation Evaluation and maintenance of concrete
9-l
Highway
299
9-Z 9-3 9-4
Maintenance
303 307 313
pavement
9-5
Highway and its environment
315
9-6 Highwaybeautification 9-7 Environmental laws
9-8 Environmental elfects of highu'ays 9-9 Construction and relation to roadside
3t7 318 319
CHAPTER
321
development
9-10 Vegetation and the highways 9-11 Parking and rest areas
321 323
THE HIGHWAY AND ITS DEVELOPMENT
CHAPTER-I0 TRAFX'IC ENGINEERING
l0-l
Road
traffic signs
I0-2 Basic principle of road signs l0-3 Warning (Danger) signs l0-4 lntersection signs l0-5 Prescription sign l0-6 Obligation signs l0-7 End of prescription signs 10-8 Direction
signs
l0-9
Informatrve sign
10-10 10-l I 10-12 10-13 10-14 10-15 10-16 10-17 10-18 10-19 10-20
Traffic signals PavEment markings Guidepost and markings Guardrail Concrete barrier Highway and urban street operations Traffic control Freeway and expressway operation
Sreet lighting Streetparking Highway capacity and level of service
325
328 329
334 339 343 345
346 349 352 360 372 377 379
382 385 386 388
390 391
1-1 Brief
llistory of Roads
Early roads with hard surfaces were found in the land of Mesopotamia. These roads were constructed as early as 3,500 B"C. Another stone surface roads were also found in the Mediterranean island of Crete, similarly constructed as those in the Western Hemisphere by thc Mayans, Aztecs and the Incas of Central South America.
The early road systems were constructed primarily for the following purposes:
l.
For the movement of armies in their conquest and for defense against invasion.
7. For transport of
food and trade
of
goods between
neighboring tovms and cities.
The Romans, who discovered cement, expanded their vast empire through extensive road networks radiating in many ditrciions from the capital city of Rome. Many of the roads built by the Romans still exist even after 2,000 years. Characteri.stically, Roman Roads were laid on three courses
L 2. 3.
A layer of small broken stones. Followed by layer of small stones mixed with mortar and then compacted firmly. Wearing course of massive stone blocks properly set and bedded with cement lnortar.
Elements of Roads and Highways
During the l7s century, under the rergn of Napoleon the Great, made a great stride on road buildings. Jerome Tresaguet (1716-1796) the famous French Engineer introduced new methods of construction and maintenance of stone roads. He improved the crown" the drainage, and the grade of the road, including the stone foundation by reducing the depth of broken stones to 25 centimeters. Tresaguet made it possible fbr Napoleon to build the massive highways of , He was accredited the title "Father of modern road building. Thirty years later, a Scottish Engineer born in Westminster Abbey, Thomas Telford (1757-1834), president and founder of the lnstitute of Civil Engineer, introduced.some improvements in the construction methods of Jerome Tresaguet. The road foundation course of Telford was made of stones having 3 inches minimum thickness. 5 inches breadth and 7 inches height. Smaller stones were driven by mauls on top voids and trued the surfaces by breaking the projecting points. Telfbrd employed a flat sub-grade, providing slight crown using stones of varying sizes. England followed the ongoing highway development started
by . The
Macadam road concept named after John (1755-1836). another famous Scottish EnMac Adam Louden gineer road builder and contemporary of Telford, was developed and widely accepted. The invention of road building equipment enhances the development of roads in Europe. In 1858, Eli Blake invented the first stone crusher and at the same period, a steam road roller weighing 30 tons was inlroduced in by its inventor, Aveling and Porter.
l-2
Early Laws that Regulates Roadway
The early Saxon Laws imposes three mandatory duties for the people to perform, namely: To repair the roads and bridges. To repair the castles and the garrisons To aid repel invasions.
l. 2. 3.
_l
The Highway and its Development After the Norman Conquest of England, it was decreed that:
1.
2.
The king's Highway is sacred. Anybody who occupies any portion thereof, by exceeding the boundaries of his land, is considered to have encroached on the king himself. Roads are for public use. All persons who want to use them may do so.
Properf owners ading the roads were required to drain the road, clip any bordering hedges, and refrain from plowing and planting trees, shrubs, or bushes closer than the specified distange from the csnter of the road.
It
was made clear that the govenment concept towards the: use of roads inciudes upholding the right of the public to use them without interference. Since the road is intended for the benefit of the people, fur return, it becomes their duty to protect and maintain the roadway.
1-3 Highways in the Philippines In the early part of 1900, transportations in this country depended largely on trails, waterways, railroad, earth roads and partially graveled roads. Highway in the Philippines at that time is nottring more than a dream to most Filipinos. The American government initiated the development of roadways in the Philippines, connecting towns, cities and provinces. The popular Macadam road type was introduced. It gained wide acceptance because ofthe abundant supply ofstones and gravel.
After the Second World War, the new independent Philippine govemmen! continued the rehabilitation and construction of roads and bridges, through the reparations and war damages paid by the Japanese government. Otler financial grants and aids received from the U.S. government were used in the construction and rehabilitation of roads and bridges.
Fifty years later, major highways and expressways were constructed through the financial assistance and loans from
Elenrents of Roads and Highways
foreign banks. Alongside with the industrialization program of the governrnent, vehicles of various types and sizes started
flooding tle roadways. Recent Land rranspor[ation records revealed that, more than 80,000 brand new -,rehicles were added to their lists everv year. At an average of 5.00 meters road occupancy by these vehicles, the DPWH must open 400 kilometers new roads every year. This data did nr:t include ),et the roaclway for second hand or surplus assembled cars. with this statistical
report, solution to traffic problems is nowhere insight. Traffic problems are expected to worsen year after year.
The 1.ear 1960 to early part of 1980 rvas consitlered an autornobile age. Cars were no longer regarded as luxury item but a necessity in transporting people and;oods, a necessity for survival, Government new concept of development is to get the farmers of the mud. It was during this clecade that road construction'ut becornes a matter of priorit-v of the governrnent under the slogan: " This nation is on Wheels,,.
1-4 Planning Dif{iculties Devefoprn*nt and maintenance of'roads ancl highways is a contmurng process alongside wrth the technological advance_ ntent. New equipment and management techniques revolution_ ized, the construction and maintenance mcthods. Advance knowledge in the field of soils, highway materials, and designs were adopted for reliability and economic considerations. Engineers are conscious
ofthe need for roadways to be safe, useful, and attractive. This needs include improvement of the roadside, erosion control, and noise abatement. They are aware
of the fact that highways are vital to the country's development. Unfortunately, highway planners are confronted with problems categorized as follows:
l. 2. ,j.
Financial
Political and 'fechnical
The Highway and its Development
The present economic condition is related to the government budgetary expenditures fbr payment of foreign clebt arnortization amounting to billions of pesos a month. Appropriations of funds for road cnnstructions and maintenance, meet severe
difliculties that sornetimes, highway development plans
are
shelves temporarily for lack of funds.
Comprehensive road development plans that are carefully studied by technical experts are twisted, or flexed down by political muscles, to suit political interests" Roads and highways plan were either; deferred- arnended or realigned for political reasons. As a consequence, different laws with conflicting purposes and procedures impede or obstruct implementations causing delay or no action at all"
Politicians now control DPVIH projects as their source of,
political funds. Highway district engineer's qualification is simply subservience to the politician. "Do wlrat I say or get out of my district". Listing of projects given to the district engineer has the corresponding name of favored contractors- the willing victims giving SOP in cash adrances.
Rational Planning is no longer the objective process, based on training, and expertise conceming the actual needs of the: people, but is rather, a political decision. Not even the Secretarl' of Public Works and Highways could say no because politics is the power that controls appropriations, budget and appointments of the president's cabinet .
As a consequence, public confidence tremendously eroded. not only in the government's ability to abate these problems, but also in the proficiency of the technical men to offer solutions. Planners are now operating in a world of rapid change. and uncertainty, in the political atmosphere where decisions by magic, or oracles, carry more weight than those based on professional training, expertise and experiences. Indeed, our professionals more particularly the technical men, seems tc have lost confidence in thyself, or eventhe solutions that they oftbr.
Blements of Roads and Highways
The Highway and its Development
1-5 Highway Programming
Direct Effects of Highway Construction and its Use
There are three inseparable sets of irrputs involved in highway progr:unming, they are:
A" Quantifiable market value l. Cost of highways as to:
l. 2.
Ecnnomic - Deals with the questions of resources. f inancial - The question of'who pays and who spends,
3.
horl much, and where? Political and istration - This invoires decision
a. b. c. d. e.
making.
trn highway programming, projects are prioritized. Those that are most economically viable were selected, if they fit into the financial capability and of course political criteria. Projects that failed on either financial or political criteria are abandoned, modified for substitute, or an alternative but shall ed rigor-
2.
b.
Highway Prograrnming Approaches
l. 2. 3. 4. 5"
c.
Financial resources are either short or long ranged implementation by the agencies functions like construction, operations, and maintenance.
Recognition
of the legislative and
istrative desire
and constraint.
Tentative priorities based on economic analysis, critical situations, present and future expected level of traffic, and
l.
7.
operation per year
Travel savings time (commercial). Net increase or decrease in travel time multiplied by the peso value of commercial time.
Motorist's safety (economic cost accident) Net change in expected number of accidents times
Cost benefits to highway :
a. b. c.
materials, including climatic conditions.
final plan and specifications. Budgetary reserve to cover emergencies like floods and other natural disasters.
Vehicles operating costs (including congestion cost) net income or decrease in costs of vehicle
B. Non-Qu antifi able Non-Market Valu e
Providing continuity of route system and coordination with other transportation mode. Selection of projects based on availability of labor and
the project implementation in coordination other agencies, acquiring right of way and making
Maintenance costs. Operating costs.
the average cost per accident per year.
claims based on political subdivisions.
6. 'wrth Scheduling
Constnrction costs.
Cost benefits to highway s
a.
ous tests.
Planning cost. Rrght of way appropriations.
Motorists safety - Accident cost of pain suffering and deprivation.
Comfort and conversion - Discomfort, inconvenience and strain of driving.
Aesthetic fiom driving viewpoint
-
Benefit of
pleasing views and scenery from road.
C. Quantifinble Non-Market Value
l.
Cost benefits to highway s - Traveling savings time. (non-commercial) Minutes save per vehicle trip.
Highways and its Development
Elements of Roads and Highways
4.
1-6 The Planner
Secure formal ratification
fiom the local officials
have the results documented
Before any project comes to reality, it has to undergo rigorous and careful studies with participation of several line agencies involved. Where proposals may be opposed or questioned by other agencies, or in the political mill, the planner appoints coordinators or catalysts, to work out in exchanging information as to the needs, goals, and altemative solutions of those who are affected, and to incorporate them into the planning and decision
lf
and
nothing goes wrong, this
step is considered final.
Good ethics demand that planners should understand that their role is to provide.knowledge and unbiased information. To be partisan and emotionally involved, will only jeopardize their credibility. 'Ihis might give them the feeling of personal defeat and disillusionment with their profession, if the solutions that they offered are only throqm into the trash can"
making
Where planners act as coordjnators, catalysts or to work as community advocates, should not be either partisan or advocate to a particular soiution. Their role is:
L 2.
To provide technical and organizational . To receive mput or information on the needs and goals
3.
affected persons group or agencies. Incorporate the above for planning and making decision.
The Functions of the Planners are:
2.
To prepare preliminary design, scoop of study and the initial work program. Know the basic needs, plan and objectives ofafilected persons. Exploration of alternatives. Data gathering by ing the representatives of other agencies involved.
Detailed analysis. Prepare detailed plan community interaction.
for
Community Involvement
In a democratic government, the public has the right to hear and be heard. Much more to participate in public hearirry where planning and decision making
of
The planner's role must be of a clarifier, expediters, conciliators and impartial negotiators. The myth of rationality must be avoided because they might believe that as professionals, they are uniquely super qualified to judge what is best for the society in their field of expertise and competence. They must accept that their personal values and goals are different from other participants.
l.
l-7
appropriate
will be conducted before
maior
decisions are made.
It is a corrunon practice to call public hearing after all major decisions were rnade and approved. Indeed, public hearing is no more than information forum for the public to know what the
istration wants for them, rather than, what the people wants from them. Public hearing should involved the public from the start of planning to give them a chance to participate in the discussions and involved thern in:
l. 2. 3. 4.
Solicit the cooperation and of public ollicials, non-goverrrment organizations, influential persons and conservative group of the community. Create special staffto carry out this function Comrnunity leadership opportunity to participate continuously rn the planning stage. Organize and develop skilled persons to conduct group meeting, workshops, hearing and other related activities.
1-8 Highway Bconomy A Country who will not avail of loans or grant from foreign
Elements of Roads and Highwnys
The Highways and its l)evelopment
financing institutions will not fbel the great impact of their infrastructure projects, if dornestic income through taxes alone will be depended on. Financing institution such as the World Bank insists that projects to which they make grants or loans be justified primarily on the economic basis. According to W. Gillespe, professor of Civil Engineering at the Union College:
Legally, the appropriation and expenditures of taxes being the people's contribution to the goverffnent must be prorated proportionally to the different provinces municipalities and cities in of infrastructure projects and not just be concentrated in specific place. Under that principle, progress of the country would be very slow considering the meager amount each province will get, and the infiastructure it will accomplish. l{ence, borrowing from foreign banks is the ultimate solutions of the government to deliver impact infrastructure projects to boost the economy and move quickly forward.
"A rninimum of expenses is of course, highly desirable; but the road which is truly the cheapest is not the one which has cost the least money, but the one which makes the mast profitable returns in proportion to the amount expended upon it. " There are many designs and istrative decjsions that does not involve public policy, but these should be made by selecting the alternative that is cheapest in the long run. Meanrng'. the result .from an econornic study tl.tat is reasonably interpreled musl prevuil.
The intent of expenditures for highways and public transportations are enumerated as follows:
]. To 2. 3. 4.
augment the country's level of economy. To provide easy access to working place. To facilitate public services; police, fire protection etc. To facilitate medical care, schooling and delivery of re-
5.
lated basic services. To give landowner benefits to transportation and increase
property assessment. Benefit to motor vehicle s through lower cost of operations and maintenance. 7.
Benefit in time saving.
8"
Less road accident.
9
To give maximum comfort and ease of travel.
Most of the country's expenditures for highways and public transport facilities are based on the principle of "Pay as you go,, Meaning, road appropriations and expenditures depend on tax collections. t(,
Arguments of those who Favors Borrowings are:
i. The need is immediate to have instant infrastructures. 2. No impact project will be seen because tJre "pay as you go" fund is scattered through out the entire road
3.
system
where the situation is most critical. Borrowings encourage investors because offast progrcss.
Counter Arguments of those Against Financing Infrastructures through Borrowing:
l. 3.
Borrowing may impair the credit rating of governrnent agencies obstructing other more important improvements. If future income is committed to pay past improvements, no more funds available to rnaintain the existing system. With much ;rmount available temptation is there to over
4.
build and recklessly spend extravagantly. Interest of the loan is a big waste of public funds.
2.
1-9 Computation and Survey Early engineering approach to highway and transportation problems were based on the results of their computations with the aid of slide rule and replaced by calculator machine. This method is time consuming and was totally discarded in the advent of computers and its appurtenances.
ll
Elements of Roads and Highways Today, most of the agencies have their oun da[a processing and reporting is done through cornputer networts. Engineering
approach
to highway
and transportation problems are done
through computer output from the simple to cr:mplex matters. Computers can do processing dota for many problems like:
l.
Projections and statistrcal studies of traffrc and transit engers.
2 3. 4. { 6. 7" 8.
9.
ror
if correctly programmed. On the other hand, too much reli-
ance on this machine might be a trap for the uninformed to assume that the program inputs are absolutely correct. Deeper analysis and professional attention to computer program is the key to accurate results that could be the basis for good deci-
1-10 Remote Sensing
Geometric. Bridges. Pavement design and maintenance. Pavement management. Scheduling for design and construction.
Computation of earthworks and other quantrties both for planning and payment of contractors.
with stereo plotter fbr map makrng
and location identification. The computer base
interactive screen, focused on
graphics could present problems into the technical matters and management decisions making lata. Various computer programs are abundantly available to solve the repetitive highway and transportation problems.
The computer graphics display a motorist view of the highway so that the engineer could make appropriate treatment of certain portion as transition from cut to fills, route, location, traffic, and transportation planning and accident analysis. The interactive graphics is used without computer, referred to as environmental simulation^ A remote controlled television camera es through small scales physical module of the area or route. The age is recorded in the tape and the playback will show impression similar to that of the walker on the road or the vehicle driver. t2
With the aid of sophisticated computers and its appurtenances, engineering practice today is not as difificult as the time of slide rule era. Computers are less prone to computational er-
sions.
Economic analysis. Financial programming.
Con"rputers are provided
The tlighways and its Development
Remote sensing is otherwise called Photogrammetry. It is the science and art of obtaining measurements by means of photography. Photogrammetry is based on aerial photographs for engineers working data on:
l. 2. 3. 4. 5. 6. 7. 8. 9.
Locations. Planning. Geometric design.
Right of way.
Traffic studies. Drainage.
Soil classifications and identifications.
Earthworkmeasurements Material location. 10. Pavement condition survev
1-11 Photogrammetric Mapping A vertical aerial photograph taken by a camera pointed almost straight downward is the most useful mapping for highway purposes. The area to be covered is photographed in parallel runs with the individual pictures lapped in the direction of the flight (end lap) and between successive runs (side lap). For stereoscopic uses, the following must be considered:
I
End lap must be greater than one half the picture width
l3
The Highways and its Development
Elements of Roads and I{ighways
2. 3.
specified not less than 55Yo nor more than 65%o in order that the center ofone picture is included in both adjacent photograph. Side lap should average at25o/o with less than 15. More than 3 5 o/o i s unacceptable. For making map purposes, the variable includes the focal length of the aerial camera, the desired combination of
map scale and contour interval, and the ratio of map scale to photograph scale.
Instruments used in converting data from aerial photo-
graphs into maps are:
]. The Kelsh and Balplex 2.
stereoscopic plotters
The wild autograph
'lhe Kern PG2
4.
The Zeiss Stereoplanigraph
Features that cannot be identified on the photographs are located by grounci measurements foy important poinfs to be included on the ground surveys are marked for easy identification on the photograph. Accuracy ofthe ground control triangulation network is when scaled with the aerial photographs. The third order triangulation is acceptable in rural areas, and the
for urban locations wherein the
maximum errors in distance are I to 5000 and 1 to 10,000 respectively. An accurate angular triangulation measurement is easily obtained by the use of Modern Theodolites. The distance measurement is carried out by an electronic distant measuring device (EDM) that employ infra red light beams, microwave or laser light. I
I
Profiles Cross sections
Cut and fill earthwork quantities The motorist view of the road
With photographs and computer record data, a separate map could be plotted easily like:
l The highways 2. The drainage 3. Housing 4. Land use and zoning 5. Property assessment The ground field survey is done only as supplemental in
J-
second order triangulation
1. 2. 3. 4.
The Photogrammetric technique coupled with digitizer, produces digital terrain models. The horizontal and vertical positions ofthe ground surface, and other photographic features are directly transferred from the matched aerial photograph to a computer data bank. The information is recalled and the computer is programmed to develop showing the following:
completing the details of those that could not be produced in the photographs.
1-12 Orthophotographs Orthophotographs is an aerial photograph corrected for scale and trlt. When the center portiol are skillfully matched and copied, they appear to be a single photograph that shows far more detail than maps. The uncorrected or partially corrected photographs are combined to form a mosaic, considered better for engineering accuracy and right ofway purposes.
1-13 Colored Photographs Aerial colored photograph presents a more detailed and precise information on traffii and parking studies. It gives clear information of the geological conditions, land use, source of materials, surfaces and sub-surface drainage. An oblique photograph is used for special studies particularly, where the ground condition is almost flat or where cliffs are so steep that a black and white photograph could not give sufficient details.
I
14
l5
I'he Ilighways and its Development
Eleltrents of ldoads and Highways
l.
l-14 Location of the Proposed Highway Early roads started from trails. Movements of people and the use of motor vehicles prompted road agencies to improve road alignment minimizing sharp curves. Road width was standardized and grades were flattened. New highway locations are trlended witJl curvature grades and other roadway elements to offer; comfortable easy driving, free flowing traffic arteries, comply with the rules on safety standards.
To improve the highways, there should be tentative plan as to the control, and minimum design speed, roadway cross sec-
2. 3. 4. 5. Stage
1.
tions, and maxlmum slope with the following considerations:
l. 2. 3. 4.
Rpliable cost cstimate. Character and hourly distribution of traffic. Economic and community benefit facLor. Availability of funds.
2.
2. 3. 4.
Reconnaissance survey of the entire area between the terminal points. Reconnaissance survey of all feasible routes. Preliminary survey of the best route. and the structure for construction.
Activities
l. 2. 3.
I
Reconnaissqnce survey of the entire area
Stereoscopic examination of small scaled aerial photographs of the area supplemented by available maps. Determination control of photography and land use.
L.ocation
of feasible routes based on photographs
maps.
Under stage
l6
II
Reconnaissance survey offeasible route:
Survey af the hest rou(e.
Preparation of large scale t,:pographic maps ustng the route photograph and Photogrammetric methods or preparation of, large scale topographic maps b-v'' ground survey guided by best route location made on photr:graphs in the second stage. Design of the preliminary location
IV Locafion 'Swn,ey
Staking of the right of way and the highway and structures for construction"
1-15 Location of Bridges
Location survey, staking of the right of way, the highway
Under stage
III Preliminary
Stage -
Locstion surveys in the rural ureas are divided into 4 stages.
l.
Stcreoscopic examination of largo-scale aerial photographs ofeach route. Detennination of the detarled control of pirotography and land use. Preparation of route maps by Photogrammetric methods. Location and comparison of feasible routes on photographs and maps" Selection ofthe best routc"
arrd
Highways and Bridges have but one purpose - To convey traffic. The location and position of a bridge is subordinate to the general alignrnent and grade. But sometimes, fuvorable alignment has to be sacrificed, only to provide a right angle crossing to small creek. Lately however, the general policy for minor roads is to determine the proper highway location, then provide the structures. A skewed bridge is comparatively more expensive than the right angle bridge. The horizontal and vertical curvature shape of large bridge presents serious design and construction problem, but the finished product may result to a better roadwav. Foundation design of piers and abutments has large effect on costs, but cost is not alw'ays the determining factor in design.
The Highways and its Development
The Highways and its DeveloPment
The cost of a bridge and its full approach cornbined before the crossing site should be determined. Bridge survey report should be accompanied with accurate data on the waterway and the historical behavior of the water. The bridge survey data shall include the foundation conditions, stream characteristics, and the adjacent structure on the stream more particularly, waterway opening.
tleir
When the location of the bndge is approximately deter-
1-16 I{ighway Plans and Specifications Plans and specifications are set of documents of instructions and conditions under which highways and bridges are built. The plan contains engineering drawings of the prolect, whereas, the specifications is a written instructions and conditions considered as integral part ofthe contract between the contractor eutd highway agency classified as legal documents.
mined, the following requirements must be considered:
1. 2. 3 4. 5. 6.
A complete data report and special survey of dre site. Prepare sketches and full scale map and profiles. The survey report must contain accurate data of the waterway for all behavior of water. There must be a complete report on the foundation condition and the stream characteristics. A complete data of the adjacent structures particularly the waterway opening.
If possible,
skewed bridge should be avoided.
The complete detailed scheme for the road which are incorporated in the geometric designS are:
1.
2. 3" 4. 5. 6. 7.
Traffic Drainage
Erosion control Roadside development
Structure Soils Pavement
Presentation of a Road Plan
l.
Source: HigthwcY Engineeing bv Calesbv ond Hicks
The upper sheet is allocated for the plan, top view showing the horizontal alignmenl, right of way takings, drain age arrangement and other features. 2. The lower half is allotted to the profile where the original elevation of the ground surface is plotted. The roadway centerline and the vertical alignment or grade line for the road is indicated. 3. The vertical scale of the profile is usually exaggeratedly enlarged from five to ten times for precise detatl. The profile and other details of the drainage, channels or connecting roads including ramps are also presented. 5. The estimated earthwork quantities for every 50 meters
station or other intervals are indicated along the bottom of each sheet along with the estimated overhead. This FIGURE 1-1 TYPICAL EXAMPLE OF SMALL BRIDGE LOCATION PROBLEM
l6
will
serve the engineer and the contractor.
l9
I lr*.
Elements of Roatls and I'iip,,ilwavs
liighwars rln{l its ilevelopment
'tr'he rolr.lwav riross sections for every situation in the rvhole pro";cr:t stretch is indicated on another sheet of the plan.
Another shcet
cf
drayiings showing
all
structures and
roattrway appurtfin;rnces ls included.
The standard sizc of
ther
drawins sheet is 55 cm x 90 cm.
Ilartial list of suhicets c.overed by the standard drawing:
1. Fipe culr,,*rts. 7. tloncr*tc box cLriverts. 3. Guard r;ril au<J pil.riipet, 4. Curbs. 5. Cutlcrs. tr Curh:lnrc'turcs '1 5 rdq:ri;rl[,s 8" Drainag* intct anil outlet structures of numerous types. 9. Manholcs" .
{ () =
o
.
3!;i .i;
J
lril
3
f
'n; l k: r:a
r{
&.
+{-
i*
v
t
ut
z
Io a
l:
F
qt
ll.
tt
o
z
.;
5
d!i
;
A. oJ UJ
t f,
o l!
10. Rip-rap and other devices used for bank protection. I l. Fences and right of way. 12. Other survey rnarkers.
The Specifications Specifications writing is generally different and a delicate rvork requiring lcnowledge of the law of contracts as well as highway practices and experiences. Specifications that are carelessly written and loosely worded may result in the use of substandard materials and poor workmanship. Mostly, it involves extra cost to the owner or the contractor and sometimes landed in court litigations. On the other hand, specifications that are too restrictive are very costly.
d a
o
Flighway Specifications is Divided into Two:
l.
2A
Stondard Specifications applies to project implemented by istration which treat the subject that repeatedly clccurs in the agency work. 7_i
Elements of Roads and Highways
2.
Special Provisions covers peculiar item of the project in question that include additional modification to standard specifications. This includes copies of all documents required in securing cornpetitive bids and contracts. Specifications are also subdivided into two: a.) The general clause that deals with the bidding procedures and award execution and control of work and other legal matters. b.) Specifuing detail regarding the materials, manner of work execution and how pay quantities are to be measured.
CHAPTER
DEG THE
HIGHWAY 2-l
Consistency
Consistency is the most important single rule
in highway
design. That is, by making every element of the roadway conforms to the expectation of every driver.
Drivers expect the highway agency to provide them with:
l.
Clear information and guidance tlrough a variety of road
2.
Avoiding abrupt changes in the traffic as well as the road
slgns. standards.
If these guides and directions could be planned properly to convey one single message at a time, and if these directions will be followed smoothly and easily without undue haste, or changes in speed, lhen, the roadway facilities are considered satisfactory. Experienced highway Engineers recommended that highway signs and directions should be integrated as early as the preliminary layout studies.
2-2 Definition of AASTHO is the American Association of State Highway ln 1914, the American Association of State Highway Officials (ASSHO) was established as an association of State Territorial and District of Coi.rmbia Highand Transportation Officials.
way Department, and the Federal Highway istration. The L3
Deg the Highway
Elements of Roads and Flighways name was expanded
in
1973, when the Departrnent of Transpor-
tation was integrated into the association renaming AASHO to AASFilO, giving the officials of these agcncy the power to govern its operation. Engineering activities, were implemented by the standing committees with the task of preparing specifications manual and standards, representing the current trighway
Control of Access is a conditron where the rights of owners or occupants of ading land or other persons access to light, air or view in cormestion with a highway is fully or partially controlled by public authority.
engineering practice.
Full Control of Access - The authority to control access is exercised to give preference to through traffic by providing access connections to seiected public roads only. Crossing at
AASIIIO
grade or direct private driveway connections is not permitted.
l. 2. 3. +.
publications includes:
Transportation Materials Specifications and Tests. Specifications for highway bridges Geometric deign standards. Numerous policy statements and guides.
Partial Control of Access - The authority to control access is exercised to give preference to through traffic. Although in addition to access connestions with selected public roads, there may be some crossings at grade and some private driveway connections allowed.
AASHTO publications are authoritative" References are made in these books and periodic manuals. 'lhe association also publishes the AASHTO quafterly reports on current Highway and Transportations sublect including trends in forecast and legislation.
Roads and Highways is defined as strips of land that have been cleared and further improved for tle movement of people and goods.
Road. R.oad has somewhat broader application in usage while generally used to describe a public thoroughfare. It can
Through Street or Through Highway - Every Highway or portion thereof on which vehicular traffic is given preferential right of way, and at the entrance to which vehicular traffic from intersecting highways is required by law to yreld right of way to vehicles on such through highway in obedience to either stop sign or yield signs erected thereon.
Parlanay is an arterial highway for non-conrmercial traffic, with full or partial control of access usually located within a park or ribbon park-like development.
also refer to railways.
Highway" The term was first used in England to describe a public road built by digging ditches on both sides and heaping up the earth in the middle creating a way higher than the adjacent land. Highway now connotes, a higher state of development than road. but the words are almost interchangeable.
Expressway is a divided arterial highway for through traffic full or partial control or access and generally provided with grade separation at major intersections. wrth
Freeway is au expressway with/r Il control
oJ"
access"
Arterial Street is an arterial route that carries traffic to the nearest access point or through traffic. It often serves as the most advantageous routes for relatively long distance travel.
Most arterial streets are existing highways of considerable length along which cross traffic is regulated by signals or stop signs. In addition, arterials provide access to adjacent property but often with restrictions on entry and exit points. Arterial street is considered as a "make do" substitute for controlled access facilities when traffic volume exceeds about 20,000 vehicles per day.
I
t
Deg the HighwaY
Elements of Roads and Highways Basic Considerations in Planning Arterial Roadways
l. 2. 3. 4. 5. 6. 7. 8.
ernment.
Accident experienced. Width should not be less than 15 meters. Must carry at least one lane oftraffic in each direction. Should be at least one kilomster in length. Should skirt neighborhood areas rather than penetrate
a given period of time usually expressed as vehicles per hour.
9.
On gnd desrgn system streets, arterials are spaced at about 600 to 900 meters apart. 10. Where accident hazard is not a factor, the minimum volume to justifu arterial road is 300 vehicles per average hour during the day, and 450 vehicles hourly during peak periods.
Sometimes, peak hour traffic volume on designated arterial road exceeds the capacrty of two-way streets, and to increase the arterial capaclty, the following solutions are enforced:
2. 3. 4. 5.
defined as a road constructed and maintained by the local gov-
Selection of the routes. Studies of the traffic volume. Origin and destination.
thern.
l.
to residence, business, or other ading properties. It is also
During peak hours, parking is prohibited on one or both sides ofthe street. Parking is prohibited several meters away from each side ofthe road intersections or corners. fughtturn is allowed on red signals anytime with care. Left turns are eliminated on congested intersections. The direction of traffic is reversed in the center lane to provide more lanes in the direction of heavier traffic flow
Collector Street form smaller mesh grid pattem where engers are pick up from service streets and carried to the arte-
rials. Large commercial enterprises or amusement facilities like drive in theaters are mostly fronting arterial roads. Local Road is defined as street or road primarily for access
Highway Capacity is defined as the manimum number of vehicles that are reasonably erpected to a given point over
l.
Under ideal conditions, one freeway lane can accommodate about 2,000 enger cars per hour.
2.
Two-lane road can carry up hour in each direction.
to 1,000
enger cars per
There is an obvious relationship betwe€n vehicle speed and highway capacity. As the volume of traffrc approaches capacity, the average speed is markedly reduced.
AADT or ADT refers to traffic volume or flow on a highway as measured by the number of vehicles lng a partial station during a given interval of time. It is called 'Average Annual Daily Traffic" if the period is less t}an one year. Volume may be stated on houdy "Observed Traffic Volume" or estimated 30e hour volume commonly used for desrgn purposes. Some highway agencies use traffic volume for 5 minutes interval to distinguish short peak movements of vehicles.
2-3 The Design Speed There is no single sst of Geometric Standards that will apply to all highways. For every highway segment, decisions reg-di"g appropriate control for each of the many details or requirements must be addressed individually or separately.
AASI{TO defined Design SPeed
as:
"The speed determined for design and correlation of the physicat feature of a highway that influence vehicles operation' 27
26
Elernents of Roads and Highwnys
Deg the Highway
It is the marimum'speed that can be maintamed over a specified section of the highway when weather and traffc conditi.ons are so
favorable that the designfeatures af the highway govern.
Basic Design Features refers to the tightness and super elevation ofcurves, the sight distance, and grade. The design speed
is
basically higher than AASI{TO recommend that:
the
anticipated average
speed.
"The design speed be set to the greatest degree possible, to satisfy the needs of nearly all drivers bath today and throughout the road anticipated life."
obsolescence as well as the increased margin of operating safety. The high speed road design must anticipate future generation high speed vehicles and advanced transportation systems that may operate on many of these road alignments. Although the design speed of most highways is govemed by construction costs, the concept of the relatively high speed design for freeways is Regardless of Cost. They are planned for a nationwide high volume traffic and high speed network.
TABLE2.l MINIMU
For economic reasons, the Geometric Features of certain road sections are designed for speed from 30 to 50 kilometers per hour. And yet, some motorists drive faster on straight road alignment or less sharply curved sections. Under this situations, highway des4n adopted control by reducing the super elevation combined with easement curves, delineators, stripprng signs and rumble strips, to alert motorists and inform them tha! they are approaching sharp curves or blind curves. Selection of the proper road design speed is one of tlre most important decisions to make, because it sets the limit to curvature, sight distance, and other geometric figures. But because of limited funds, there is a strong ternptation to reduce the design speed. Such kind of decision is unwise, because the alignment grade and siglrt distance after the roadway has been construct€d and paved along the landscape and rights of way, become more difficult and expensive to adjust or to correct.
The AASHTO practice is to classify first the highway as Rural or Urban, then as Freeways, Arterials, Coliectors and Local. Rural collectors and local facilities are classified as flat, rolling, or mountainous. Although the design speed presently used is 80 lan. per hour, highway designers projected design speed up ta 120 kilometers per hour to guarantee against future
28
ECOMMENDEI' DESIGN SPEED
FACILITY
RURAL Km/hr 8G95 preferred 6495 but 48 in built
Freeway
Arterial Collectors Local
110-95 mountainous 80- I
l0
up areas 48 km./hr.
See Table 2-2
32-48km./hr.
See Table 2-2
TABLE 2.2 AASHTO MINIMUM DESIGN SPEEI) KM./HR FOR RURAL COLLECTORS AND LOCAL ROADS BASED ON CURRENT ADT Class
Collector
0-400 Level
4W-750
750-2000
Tra 2000-4000 Over 4000 75 90
60 45
75
I>
Rolling
60
60
IJ
75
Mountainous
30
45 50-250 45
45
60
60
250-400
Over 400
Local
0-50
Levcl Rolling
45 30
Mountainous
30
45
60 45
30
30
75 60 45
2-4 Cross Section of Typical Highway The cross section of a typical highway has latitude of variables to consider such as:
Deg the Highway
Elements of Roads and l{ighways The volume of traffic. Character of the traffic. Speed of the
traffic.
Characteristics of motor vehicles and of the driver
Highway design usually adopted cross section that is uniform in thickness from end to end of the improvement. This is acceptable on high volume traffic road facilities. For a low volume traffic facilities, modrfication of the features like the shouldcrs width in rough areas are usually employed to reduce costs. A cross section design generally offers the expected level of service for safety and a recent study showed that: t.
A
7.20 meters wide pavement has l8% less accidenl compared wrth pavement narrower than 5.50 m. wide.
A 3.
4.
7,2A meters wide pavement ha 4%o fetver accidents
than the 6.00 meters wide roadway. Accident records showed no difference between the 6.60 meters and the 7.20 meters wide pave.ment. For the 6.00 m., 6.60 m. and,7.20 meters wide pavement with 2.70 to 3.00 m. wide shoulder, recorded accident decreases by 30% compared to 0 to .60 m. wide shoulder. And 20%o compared with a .90 to 1.20 meters wide shoulder.
It appears that, the above difference in accident potentials may not justifiz higher standard, particularly, when traffic volume is low. A driver's instinct when overtaking or allowing other cars to overtake or meting oncoming vehicles is to look at the surface width of the highway, and see the kind of surface where to position his car. Originally, the total surface width of the roadway was only 4.50 meters, but due to the increased number of vehicles using the roadway, the width was adjusted to 4.80 to 5.40 meters. Lately, the width of the road was standardized to 3.00 m. for first class paved one lane highway, and now 3.60 meters wide surface was adopted standard for freeways and other major traf30
t
fic
roadways, although tlere are strong demand further from 3.60 to 4.20 meters.
to
increase
it
For Two Lane Rural Highways, a 7.20 meters wide surface is required for safe clearance between commercial vehicles and is recornmended for main highways. For Collector Roadway, 6.00 meters wide surface is acceptable only for low volume trafFrc including few trucks traveling thereon.
For Local Rural Roadway, the minimum surface width is 4.80 meters for a 30 km / hr. design speed.
For Urbair Roadway, the minimum design width is 3.60 meters although 3.00 meters is allowed where space is limited. Where there are heavy meetings or overtaking between cars and trucks, air disturbances sometimes cause side collision between ing vehicles when sweryed within or out of their lanes. Motorists are requesting for wider lanes. Rounded 2:1 cut alope in deep cut
FIGURE 2-1 CROSS SECTION OF ryPICAL TWO LANE HIGHWAYS
FTGURE
2-2 MULT|-LANE HTGHWAYS AND FREEWAYS (HALF
SECTTON)
3l
Deg the Highway
Elements of Roads and Highways
I
100
2.50
3.25
13.00
3.25
2.54
Widening 0.20
0.15
0.15
0.20
L-
t I
!r...F-.?F Vr. < 100 Km / hr. Four 3.50 m. Lanes - 2.50 m. Stop Lanes
StoD lane
stop ranJ Shoulder
1.00
Medran
Travelway
I
Travelway
Shouldel
Roadway 33.50
Yr.
12O
Km / hr. or Vr < 100 km/hr. with 13 m. Median - 2.50 m. Stop Lanes
Vr.
Vr.
>
100 Km /
hr.
<
60 Km / hr. Four 3.00 m.
Lanes
-
250 Stop Lanes
2.50 Stop Lanes
Vr. < 100 Km /
hr.
Two - 3.50 m. Lanes 2.00 m. Stop lenes
23.50
Vr
<
100 Km / hr. 2.50 Stop Lanes
Vr. < 80 Km,/ hr. Two - 3.00 m. Laner 2.00 m. Stop lanes
22.O0
Vr.
< 60 Km /
FIGURE
32
Lr-
23
hr.
2.50 Stop Lanes
FIGURE
DIVIDEO HIGHWAYS
33
2-4 UNDIVIDED HIGHWAYS
t
Elements of Roads and Highways
2-5 Road Shoulder
Deg the Highway
Policy on Geometric Design Recommended that:
Road shoulder or verge is defined as that portion of the roadway between the edge of the traffic lane and the edge of the ditch, gutter, curb or side slope. AASHTO requires that its us-
l.
able pavement width shall be strong enough to vehicles.
2.
Importance of Road Shoulder
3.
1. 2.
Road shoulder serves as a place for vehicles to stop when disabled or for some other purpc,ses. Road shoulder considerably reduces road accidents. -l'he road capacity is decreased and accident opporrunity increases if the shoulder is too narrow or omitted in the
4. 5.
meters wide is much preferred. When the design hour volume
6.
For Urban Arterial Road, similar shoulder without curb
design.
3.
Shoulder should be continuous along the full length of the roadway. It also adds structural strength to the road pavement.
4.
Shouldlr increases the horizontal sight distance
on curves. It reduces accident potential when vehicle stop during emergencies.
Most of the road shoulders in rural areas are unpaved having a width of 60 to 120 centimeters wide either earth filled or graveled surface that during rainy days, drivers are hesitant to occupy. The Uniform Traffic Control Device Manual provides that:
Outside shoulder should be paved for at least 3.00 or 3.60 meters wide if tnrck volume is more than 250 in the design hour (ADT). The recommended width of left (median) shoulder is 1.20 to 2.40 meters with at ldast 1.20 msters paved. If there are 6 or more lanes, the median shoulder should be 3.00 meters wide or 3.60 metbrs if truck volume in the desrgn hour exceeds 250. For arterials with ADT less than 400 the usable shoulder width is fixed at 1.20 meters minimum, although 2.40
ADT exceeds 400, the usable minimum shoulder width is 2"40 meters although 3.60 meters is recommended.
is suggested unless needed for proposed drainage. The width of median shoulder on four lanes divided arterials is fixed at 90 centimeters as minimum. 8. For six or more lanes, 2.40 to 3.00 meters shoulder width is recommended. 9. For Rural Collectors Roadway, 60 centimeters wide graded shoulder is required for ADT's less than 400" 10. For ADT's over 2000. 2.40 meters wide shoulder is rec-
7.
ommended.
TABLE 2.3 WIDTH OFROADWAY X'ORUNDIVIDED HTGHWAY Total Trave
" All inter-town or city highways shall
provided with edge line and may be used on other classes of roads."
A
be
continuous narrow white line strip at the edge of the roadway that separates the shoulder, serves as guide to drivers during bad weather and poor visibilrty conditions. The white strips tend the driver to stay in the traffrc lane and the vehicles seldom infringe on the shoulder. )4
Shoulder Width
Roadway Width
of
Refcrence
100-80-60-40
14.00 m. 12.00 m.
3.25
20.50
3.25
18.50
60-40
7.00 m. 7.00 m.
2.75
12.50
2.00 2.7s 2.00
I1.00 10.70
2.75
11.50
1.50
9.00
100-80-60-40 80-60-40 100-80-60-40 80-60-40 80-60-40 80-60-40
6.70 m. 6.7C m.
6.00 m. 6.00 m.
12.20
35
Deg the Highway
r\lements of Roads and Highways
ONLY WITH STOP . LANE 15 Widening
Travelway
Stop
Lane
2.50
m.
or2.25 or 2.00m. shoulder 3.25 m. or 3.30 m.
or 2.75
Stop Lane 2.50 or2.25 or 2.00
nan
0.50
m.
RoundinO 1.00
S
stope or Ditch Stop Lanes 2.50 a( 2.25 ot 2.OO
Turfed
3.00 2.0O
l/4 to
to
Wall
3.00
1/16
UNDER STRUCTURE
Natural Soil 1.20
WITH STOP LANE AND GUARDRAILS
lq
f ravelway
5%
Stop Lane 2.50. 2.25 or 2.00
I
7% 0.75
Shoulder 3.25 , 3.00 or 2.75
Concrete
0.75 ON STRUCTURE
Covered gutter
Lane 2.50, 2.25 or 2.00
FIGURE
2{
FIGURE
STRAIGHT ALIGfTIMENT SHOULDER DETAIL WITH STOP I.ANE
24
STRAIGHT ALTGNMENT SHOULDER DETATL WITH STOP
LAilE AND GUARDRAIL
Elements of Roads and Highways
Deg the Highway NO STOP LANE, FOOTPATH OR GUARDRAILS ( NO PEDESTRIAN ALLOWED)
UNDER STRUCTURE
Shoulder 2.00, 1.50 or
1-00
WITH STOP LANE USED AS CYCLE PATH AND FOOTPATH
ON STRUCTURE Stop Lane / cycle path 2.5O or 2.25 ot 2.OO
UNDER STRUCTURE
A=
Stop Lane / cycle path 2.50, 2.25 ar 2.OO
Stop Lane / cycle path / footpath 2.5a, 2.25 ot 2.oO
A=
1.50 ifvr > 60Km/hr. 1.25 if Vr S 60 Km /hr.
Under Structure
0.50
Shoulder 2.00.1.50 -
if
1.00 shouldef
1
Stop Lane/ cycle path
?.50. 2.25
FIGURE
38
ot
2.OO
2-7 STRAIGHT ALIGNMENT SHOULDER DETAIL WITH STOP LANE USED AS CYCLE PATH AtlD FOOTPATH
ON STRUCTURE
FIGURE
2€
NO STOP LANE, I,IO FOOTPATH, I{O GUARDRAILS SHOULDER
39
I
Deg the Highway
Elements of Roads and Highways FOOTPATH ONLY
I.IT{SIDE SHOULDER
Footpath 1.25
- 2.00 -
1.75
-
1.50
Paved stop
if e<4%
if e<5%
if e>4% S=e if e>5% S=e
STRUCTURE 2. OUTSIDE SHOULDER
WITH FOOTPATH ANO GUARDRAILS
Footpath 75 - .50 - or .50
if
1.00 shoulder
UNDER STRUCTURE A = 1.50 if Vr > 60 km/ hr. A = 1.25 if Vr.l 60 km/ hr.
Shouldcr 3.00 or 2.50
FIGURE
2€
SHOULDER DETAIL FOOTPATI{ ONLY
FIGURE 2-10 ALIGIIIMENT ltrl CURVE SHOULDER OETATL
Elements of Roads and Highways Considering the above recommendations, Width is defined as "extendingfrom the edge of the surfacing to the point where shoulder slope intersect the side slope. " The Urban colleclor road usually has no shoulder, instead, parking lanes of 2.40 me' ters or preferably 3.00 meters wide with gutters are specified.
Deg the Highway These types
of cross sections allow the inner lane to acit is flatter than the outer
commodate high speed traffic because lanes.
On a very wide street, the parabolic crown surface makes the centerline almost flat unless gutters are sufficiently deep enough to convey water. A combination of uniform slope with parabolic curve is used instead of ttre parabolic sections.
2-6 The Cross Slope The cross slope is provided in all tangent sections of the roadway. Slope usually falls in both directions from the ce,lrterline of the uro lane highway except where super elevation of
Slope 1% to 2%
curyes directs all water towards the inside.
For high type pavemen! the crown or slope is often Iyo tD 2o/o. However, steqter slopes are strongly recommended because rain water, flow away more rapidly reducing the water thickness on the road pavement. A cross slope in one direction of multi lane hrghways makes driving comfortable, but with heavy rainfall, the water depth increases on the roadwqy.
FIGURE
2.12 HIGH TYPE PAVEMENT CROSS SLOP€
i
Center Line
FIGURE 2.13 PARABOLIC PAVEMENT SECTION
FIGURE 2.1 1 PAVED AND GRAVEL SHOULDER CROSS SLOPE
The paved shoulder cross slope ranges from3o/ota 6% although 4Yo is the most cornmon. For a gravel shoulder, 4%to 60/o slope is satisfactory and 7o/o slope is effective drainage for turf (grass) surfaces.
42
2-7 Cut or Fill
Slope
Eadh fill of normal height is safe on a slope of I:2 ratios. Meaning, the first number represents the horizontal distance while the second number is the vertical distance. 43
Elements of Roads and Highw*ys
Deg the Highway 2. 3.
EARTHFILL OF NORMAL HEIGHT 1: 2 RATIO
FIGURE
CUTS THROUGH ORDINARY UNDISTURBED EARTH 1:1 RATIO
2.14
FIGURE 2.15
Slope of cuts through an ordinary undisturbed earthfill remain in place with a ratio of 1:1 slope. On the otlrer hand, rock cuts could be as steep as l:2 and sometimes 1:4 proven to be stable. Receirtly, slopes had been geirerally lowered for safer operations and to facilitate plant growth. Plants reduced erosion and decreases maintenance costs.
Advantages of Flat Side or Back Slope
l. 2. 3.
With back slope of 3:l or even flatter, cars could be directed to back into the road and will come to stop or continue down the slope with no risk of over turning. Flat fill slopes are visible from the vehicles at full extent grirng the roadway safer appearance. With visible slope for being low and fla! vehicles could be positioned or parked closer to the edge, and on two lane roadway facilities parkmg would be farttrer from the opposlng traffic.
Recommended Policy on Geometric Design
1.
The 6:l slope ratio could be adopted on embankment than 1.20 meters high, and 4:l ratio on a higher fill.
less
The 2:1 slope is allowed to heights greater than 6.00 m. Cut slope should not be steeper than 2:l ratio except on solid rock or special kind of soil.
VISIBLE FLAT SLOPE
ROCK CUTS RATIO FROM 1:2 ro 1:4
FIGURE 2-16 ROCKCUT RATIO FROM 1:2 OR 1:4
The AASHTO policy stipulated that where cut or fill slopes intersect the original ground surface, cross section must be rounded to blend the slope with the natural ground surface. When the side slope requires e,nrbankrnent with suitable retaintng urall, any of the following materials could be used dependrqg uponthe natural conditions.
l. Fland placed stones. 2. Cerre,nt nrbbles masonry. 3. Concrete blocks. 4. Conventional reinforced concrete. 5. T or counter forted designs. 6. Cribs assembled fromtimber. 7. Precast concrete. 8. Metal elements.
,,./,
Deg the HighwaY
Elements of Roads and HighwaYs
9. Tied back piling. 10. Earth reinforced with metal or plastic bands' 2-8 Number of Lanes The number of lanes in a segment of the highway is determined from tJre estimated traffic volume for the design year (AADT) and highway lane capacity at expected level of service. AASFilO policies accept a dually divided 16 lanes roadway with four lanes in each direction for an inner freeway and four more lanes in each direction on the outside. There are some instances where a reversible lane is located at the center of freeways with unbalanced heavy traffic flow.
Curved median with 1.20 to 1.80 meters width serves as partition - separation of opposite traffic control devices.
10.
The width of a traversable median should be wide enough to prevent vehicles running out of control from
l.
The 15 to 24 meters distance between landed edges is favored, but specific value is not-stipulated.
12. Cross slope of the median should not be greater than 6:1
butpreferably l0:1. 13. Dense planting ofrose hedges serves as safety crash barriers.
For Narrow Median, there are four means of reducing cross median accidents:
tages:
l.
It is an effective means of reducing
2.
flicts, and accident between opposing streams of traffic. The Median offers refuge between opposing traffic stream ofcross traffic, and pedestrian could traverse each
7.
9.
I
Recently, median in various forms, becomes absolute requrrement for highways because, it offers the following advan-
6.
Medians with 6 to 18 meters wide allow drivers to cross each roadway separately. A 4.20 to 6.60 meters median width provides protection for turning vehicles'
reaching the opposite traffic.
2-9 Highway Median
3. 4. 5.
8.
1. 2. 3. 4.
headlight glares, con-
strearn at separate maneuvers. Median provides available space for left tum lanes. It makes turning of vehicles smooth and safe operation.
Provide Provide Provide Provide
detemng devices. non-traversable energy absorbing barriers' non-traversable rigid barriers. G.M. barriers.
Deterring Devices. - Two sets of double strip painted on the existing pavement, raised diagonal bars, low curbing and
Where space and cost permit, wide median is highly recommended. For rural sections of freeway, the 18 to 27
shallow ditches.
Non-Traversable Energy Absorbing Devices. The line chain link fence I meter high ed by steel post augmented by cables at the bottom and midpoint. Non-traversable rigid barriers are metal guard rail.
msters wide median is being adopted. The Policy on Geometric Design states that, 3.00 to 9.00 meters median width is appropriate in suburban or mountainous situations.
For rural and urban arterials, 18.00 meters median or wider is preferred because it allows the use of independent profiles and at the same time minimizes cross over
G.M. Barriers. A high non-mountain sloped face concrete barriers called New Jersey. It is cast or extruded in place or precast in section and set in position by crane.
accident.
47
46 _t
Deg the Highway
Elements of Roads and Highways
.20 Widening
Widening h = .02 to.04
Vr.
120 km /
hr. or eventually Vr. 100 km.l hr.
Vr. <1(X) kmlhr.
Turf or stabilization 5.60
Vr. < 100 km I hr.
5
D
___r---*
r-*t 1.00 |
I
Vr.
]
I
ll T_l
I
stabilization 1.80
Turf oi stabilization
.20 S
S'
|.-l
Stabilization 1.80
|
> 80 km / hr.
Vr. 3 00 km I hr. Vr. < 100 km I hr. FIGURE
2.I7
MEDIATTI
UNDER STRUCTURE FIGURE
48
2-t8 STRAIGIIT ALIGNMENT MEDlAltl lltl CURREilT
SECTION
49
Deg the Highway
Elements of Roads and Highways
--fi V
O1
ol dl
6, ol
J
ov@
:-
^qo Noo
9': @aio
3*3 ooo
r
€oY
I
E
09'e ol 00 e
I I
I
T
o
z s ul
=
Medlan > 3.00 meters
FIGURE
50
2.I9
MEDIAN ON STRUCTURES
F]GURE
2.20 MEDIAfII APPROACH
5l
1 Elements of Roads and Highways
Deg the llighway
{
BARRIER CURB
5
12.5
lN'ul,o tll
a=z.s/
I
I .7
ot rut zt
5l zl
10
ol FI
ffil q, zl
'l
10 I
20
ll \---t-r 'll?
Stope 30:20
(
I
repForls I I I
FIGURE 2-
22 MOUNTABLE CURB
2-10 The Grade Line Grade line is defined as the longitudinal profile of the highway as a measure how the centerline of the highway rises and
FIGURE 2.2,I DECELERATION LANES A]iIO II{SERTION LAiIES
fall.
Deg the Highway
Elements of Roads and Highways \o
!c
cil
The grade line appears on a profile taken along the road It is a series of straight lines connected by parabolic vertical curves to which straight grades are tangent.
o d
centerline.
F]
p
oo
=9o\.o\o
o E]
s z
€
€C-F-\On
1.
c{oo
Fl
o\
(h
o
I *o
In laying the grade line, the designer must consider the following:
2.
oo
90\€c-\o
q)
o
l&
t-
C-
F-
\O
3.
ral
rr
a FI o 4 trl
j
E
tn
"l
z
oo
&
ti
u)
=9a€ O\€l"-\O
.2 €F-\or
a
xtsl
Fl
Undesirable native soil should be provided with suffi-
5.
cient covering. Grade line elevations along the river or stream, erned by the expected level of water flood.
is gov-
q)
o
nssS
V)
&n -d
6
E
$cnco(a
! a.l
F]
\o
u)
\o
ao
B frl
rat !f
!? Fl Xg H,O o-
'tr9 9? q> ,R6 v5 og
>:()
r4
=o. tuz cf)
xg 54
drainage purposes.
4.
q
oo
X
tr tr
fte grade line must be considered balanced excavation against embankrnents to get the minimum overall cost. In flat are4 the grade line is set almost parallel to the ground surface but sufficiently above the ground for
2-11 Vertical Curve Over Crest
r-\O\Or
E
j
main consideration. In mountainous areas,
x
E A E
Where earthwork is minimal and consistently meeting sigtrt distances in relation to grade line, economy is one
E
$$38hpi
I
U)
All vertical curves should not be shorter than the established minimum over crests. This is govemed by the sight distance requirements but sometimes a case of riding, may demand longer curves than the sight distance. Some designers prefer no vertical curye to be shorter than 300 meters. AASHTO 5t'ggested that the minimum curve lengtb varies with the design speed in meters distance equals to 8 times the velocity in kilometers per hour.
" The vertical distance from the intersecfion ofthe straight grade line to the curve is equal to one eight ofthe product oJthe algebraic dffirence in grades and the length of the curve in stations. This is called the maximum correction. TIte rate at which the curve departs vertically from both tangent grade line 55
Elements of Roads and Highways
Deg the Highway
is proportional to the square of the horizontal distance from the end of the curve. The correction at any intermediate point is obtained by:
l. Z.
Multiplyrng the maximum correction by the square of the horizontal distance between the near end of the curve and the point. Divide this product by the square of one half the length
2-13 Stopping Sight Distance The stopping sight distance is defined as the longest disof an object 15 centimeters (6") above the road surface where the design height of the driver's eye abovc the pavement is 105 centimeters. tance that a driver could see the top
ofthe curve.
2-12 Right of Way Acquisition of land for the right of way is very costly. Based on experience from the past, highway agency now consider it a good practice to acquire right of way wide enough to sufficiently provide for the ultimate expected development. A successful freeway and expressway operations, closes the roadway from direct access to ading property and some 1o-
cal roads or streets. If local traffic and land use are to be opened, it must be served by service roads originally planned as part of the main freeway. Frontage road shall be permitted m enter coruresfing cross streets only at a distance of at least 100 meters for rural road and 50 meters f,or urban conditions.
of
Frontagc No Frontage Road
Road
2
60
45
4
68
53
Lanes
6 8
Source:
83
Rcstricted No Normal with
Frontace Rd.
FIGURE 2-23 MEASURING STOPPING SIGHT DISTANCE
Stopping Distance is Made-up of Two Elements
l.
The distance traveled after the obstruction or object is seen and before the driver applies the brakes. The second distance is consumed while the driver applies brakes for the vehicle to stop. The distance covered could be expressed by the following formula:
URBAN
RURAL
width
Object 15 cm. above the pavement
Z.
TABLE 2-5 MINIMTM RIGHT OF WAY WIDTHS FOR RI]RAL AND URBAN F'RDEWAYS AT GRADE IN METER Number
1.05 m. eye level
Normal No
d: tm/s
Rd
Frontacc Rd. F
Breakingdistance:
60
4l 5l
89
53
68
59
96
60
d: (m/s)2 19.6 f
A Policy on Geometric Design
Where 56
d : (m/s)2 2 gmf
:
m,/s
-
Initial speed, in meter per second 57
Elements of Roads and Highways
Deg the Highway
t = Detection,
recognition, decision and response initiation ( brake reaction time ) Acceleration of gravity, 9.80 meters per second squared Coefficient of friction between the tire and pavement.
gm =
f=
2-14 The ing Sight Distance
The above formula assumes that the highway level is flat. If the car is traveling uphill, the braking distance is decreased, and for downhill, braking distance is increased. 'lhe braking distance on slope is expressed by the following formula: Braking distance (m)
d = (.m/ s )2
g=
/
a/o
100
2{
Specd
Break Reaction
for Time Dstance
Km/ph Condition
Sec.
Mctcr
-
30 45 60
30-32 40-50
2.5
22-24
2.5
55-60
2.5
3l-33 4044
L:
:
4=
length required ofvertical curve specified sight distance algebraic difference in grades expressed in perceirt
75
65-75
90
80-90
48-55 57-66
inc Sicht Di Cocf.
100
85-95
2.5 2.5 2.5
105
90-100
2.5
&77
110
90-ll0
2.5
67-83
120
95-120
2.5
71.88
0.27
A Policy
6t-71
on Gcomctric Dcsign
of
Friction 0.40 0.35 0.32 0.30 0.29 0.29 0.28 0.28
Source:
Computed m€tcr
3r.8-35.8
Rounded for Design (rn.)
36-38 60-60
53.4-58.8 80.1-94.2 I12.8-138.3
112-142
r50.2-t90.2
I 57-195
t65.0-217.2 183.9-252.0 200.1-283.0 222.3-324.9
165-2t7
82-97
181.255
202-285 225-330
FIGURE 2-
24 MEASURING ING SIGHT DISTANCE
The design of two lane highway of ing over crests is generally practical only cn flat grades because the longer vertical curves are required to provide ing sight than stopping sight distance.
F = (m/s)i 9.8 Rm
58
L
Ii'INIMUM STOPPING SIGHT DISTANCE WET ROAD
Dcsign Assumed Specd
than
A
S
Uphill grade is positive ( + ) Downhill grade is negative ( - ) TABLE
L : 25 - 943 where S is greater
where S is less than L L is lurgth in meters 943
Longitudinal slope of tlre roadway or Grade
,
L : AS2
1e.8(f+g)
Where:
The ing sight distance is the longest distance that a driver can see the top of an oncoming vehicle where the driver's eye level is 1.05 mgters above the pavement surface. The relationship between the ing sight distance, the algebraic difference in grades, and the length ofvertical curve is represented by the following equations:
Se
Elements of Roads and Highways
Where:
Deg the Highway
s) : Meter per second Rm : Radius in mster Se = Super elevation (slope ratio) rise
(m /
per second
The maximum coefficient of side friction on dry pavement as determlned by curve tests ranges between 0.4 and 0.5 value with normal pavemsnt and smooth tires is about 0.35 at 75 kilometers per hour. TABLE 2.7 AASHTO MIMMUM ING SIGI{T DISTAI{CE FON DESIGN
T}f TWO-I.ANE I{IGIfl$AYS Minimum ing
invite accident. Similarly, deg circular curves of differem radius from end to end or compounded curve is not a good practice, unless suitable transitions between them are provided. To have a short tangent between two curves is also a poor practice. A long flat curve is acceptable at all times. It is pieas-
ing to look at, with less probability of future obsolescence. Alignment should be provided with tangent because there are drivers who hesitate to on curyes. A short curve appears like kinks. A long flat curve is preferred for small changis in direction.
2-L6 Circular Curves
Ovcrtaking Vehicle
Km/hr. 35
35
48
243
50 65
42
58 70
327
80
65
82
552
5s0
95
75
9l
&2
u0
100
80
96
693
690
110
86
l0:.
747
740
t20
90
105
780
135
95
ll0
780 822
))
244 320 440
,i'11
820
TABLE 2-8 AASHTO RECOMMENDED MAXIMUM COEFFICIENT OF SIDE FRICTION Design Spced Km/hr.
48
Cocflicient of Friction
.16
ll3 .10
A vehicle traveling in curved road is subject to centrifugal force. This force is balanced by equal and opposite forces developed through the super elevation and side frictions. However, neither the side friction on the super elevation, could overcome nor exceed the maximum control and limit on the sharpness of the curves with a prescribed design speed. The sharpness of a curve is dependent on its radius. Sharpness is expressed in of the curve degrees, and the degrees of curve is inversely proportional with the radius.
Formula: D =
5.729.58
=
5.129.58
Radius
Rrdi* D
129 .08
2-15 Road Alignment
Where: D = degree of curve and the radius Degree of curve SI : 0.328 D Solution using the above formula will give
following results: Road alignment should be consistent. An abrupt change from flat to sharp curve and long tangents followed by sharp curve should be avoided because it will onlv create hazard and 60
The degree of curve is expressed either by the Arc definitions or the Chord definitions.
6l
Elements of Roads and Highways
Deg the Highway
l.
TABLE 2-9 DEGREE OF CT]RVES
of
Rndirs Meter
30' lo 00' 20 00'
3A9r.7s
00
Decree of Curvc 60 00'
291.06
00' 00'
t't4.63
100
1,146.38 873.19
Radius
200
2.
per elevation.
87.32
Arc Definitions - The degree of curve is the central angle subtended by a 30 meters arc ofthe curve. Chord Definitions - The degree of curve is the central angle subtended by 50 meters chord. Radius
=
50 Sine % D
TABLE 2.10 SHARPEST PERMISSIBLE HORIZONTAL CT]RVES FOR GIVEN DESIGN SPEED AND SI]PER ELEVATION MaximumPermissible Degree of Curve D, or Minimum Radius Design Speed
Km/hr. Super
Elev. 0.04
0.10
Condition for use Dcsirable for down arterials
35 50 65 80 91 t13 .t7
.16
.15
.t4
.13
6 291
3.7s 466
.12
D
45
19
l0
Rm
39
92
175
Max for Rural
D
58
8.25
5.25
3.5
Rm
30
25 70
13.25
highway and
132
198
333
499
For design speed of 50 kilometers per hour, the normal cross slope is l'- 21' or even flatter curves. For a 120 kilometers per hour design speed road, the nofmal cross slope is 0'- 15' or flatter curves without su-
121
ln each of this solution, the total side friction 0.04 for an adverse cross slope of 0.02.
2-17 Super Elevation -,Runoff Curved sections of roadways are usually super elevated. Provisions for gradual changes from one point to the other should be considered. The centerline of each individual roadway at profile grade is maintained while raising the outer edge and lowering the inner edge to attain the desired super elevation. It is done by raising-up the outside edge of the pavement with relation to the centerline until the outer half of the cross section is flat. Then, the outer edge is raised until the cross section is straight. Finally, the e,lrtire cross section is rotated as a whole until firll super elevation is reached.
.ll
2.25 776
suburban frccway
Sourcc: A Policy on Gcometric Design
The maximum allowed super elevation rate before was 0.12 but now it is 0.10 except on low volume gravel roads. The Policy on Geometric Design recommend that : 62
is less than
Lane surface
FIGURE 2-25 SUPER ELEVATION OF CURVES
Deg the Highway
Elements of Roads and Highways TABLE 2.1I SUGGESTED MII{IMI.]M LENGTII OF SIJPER ELEVATION RI]NOFF F'OR2-LANE A3.60 METERS LANE
LENGTH OF RUNOFF FORDESIGN SPEED in Meter Super clevation Rate Km./hr. .02 .04 .06 .08 .10
35
9.0 18.0 28.5 37 .5 48.0
95
50
10.5 2r.0 33.0 43.5 54.0
12.0 15.0 25.5 28.5 37.5 43.5 5l .0 57 .0 63.0 72.0
16.5 33.0 48.0 @.5 8r.0
ll5
18.0 36.0 54.0 72.0 90.0
130
19.5
39.0 60.0 79 5
AASHTO recornmended the run off leirgth to vary both with the super elwation rate and the design spee4 but with minimum sst for appearance and comfort to riders. A roadway that lies in a cut, where the grade line is nearly flat, may create sag by lowering its inner edge. This may not drain surface water.
It is advisable to make the super elevation by raising the outer edge elevated tvrice ttre usual distance. Where the alignment is of tangent connected by a circular curve, super elevation is started on a tange,ft before tlrc curve is reached and full super elwation is accomplished at a distance beyond the point of curve. It is therefore recornmended that 600A ta 80% of the runoffbe on a tangent. For wider roadway, the length give,n on Table 2-9 should be
Four lanes, individual value increased by 50% Six lanes, individual value increased by 100%
A provision for a wider roadway is necessary on sharp curve for two lanes pavement under the following reasons:
l. 2. 3. 4.
To force the drivers to shy away from the pavernent edge. To increase the effective transverse vehicle width for nontracking of front and rear wheels. To give additional width due to the slanted position of the front wheel to the roadway center line. For a7.20 msters wide roadway, an additional width of 30 centimeters is necessary on an'open curve highway.
99.0
Sourcc: A Policy on Geometric Design
increased as follows:
2-t8 Widening of Curves
Reverse circular curves are seldom used on modern highways, but reverse cuwes that are provided with proper length easemsnts between them are acceptable. If no easement curve is allotted, curves on opposite directions should be separated by tangent several meters long. There are roads with compound curves that change abruptly
from one sharpness to another. Where the radii of the compound curves are Jifferent, sudden change confuse the drivers and in turn they shift position within the lane and sometimes veer out of it. For this reason, compound circular curve of different radii is considered as poor design. recommends that the radius of the flatter curve for rural highways should never be more than 50olo greater than
AASFilO
that of the sharper one. For urban intersection, this easement curve is considered which introduces the changes in radius gradually. Super elevation changes along this transition section.
2-19 Island An island is a defined area bstwesn traffic lanes for control of vehicle movement and for pedestrian refuge. Within an intersection, median is considered an island. This definition makes evident that an island is no single physical type. 65
_ T
Elements of Roads and Highways
Deg the Highway
It may range from an area delineated by barrier curb to a pavement area marked by paint. On at-grade intersection in which traffic is directed into definite paths by island is termed as Channelized Intersections.
Island is included in the design of intersections for the following purposes:
l. 2. 3. 4.
Separation of vehicular flows. Separation of conflicts. Reduction in excessive pavement areas.
The angle between intersecting streams of traffic can be smooth
6.
Prohibited turns may be prevented
and favorable
Reduction of traffic and indications of proper use of intersections.
5
Mlf
Arrangement to favor a promineirt turning movemerf. Location of traffic control devices.
To confine vehicles in a definite location without proper route for vehicles and pedestrian, everyone's action could not be predicted by others and these are usually the main cause of confrsion which lead to accidents. By
charurelization, the angle
streams
or route between intersecting
of traffic can be smooth and favorable. Drivers are
commanded to merge into moving traffic strearns at flat angle and right speed being controlled over vehicles approaching an
A ItH'l
Speed of vehicles controlled over approaching intersections
T
Funneling vehicles into narrowing opening prevent oveftaking and ing conflict area
intersection.
When cross traffic meets at flat angle, head on collision cotrld be more serious. A right angle at 75'to 105" is most favorable glving the driver that opportunity to assess or calculate the position and speed of oncoming vehicles. By channelization, funneling is also effective in preventing overtaking and ing in conflict areas. A well studied super elevation is an imporfant adjunct to channelization that regulates the vehicle speed and:
1.
Prohibited turns are prevented.
r*
-ll/t( II tl
Ir Refuge provided for turning
vehicles
Drivers commanded to merge into moving trafftc streams.
FIGURE 2- 26 GENERAL TYPES AND SHAPES OF AN ISLAND
-
Elements of Roads and Highways
3.
By channelization, refuge may be provided for turning or
4.
The drivers has to face only one decision at a time,
crossing velucles and pedestrians. hence, conflicts can be avoided.
5. It provides location
for the traffic control devices like
Deg the Highway Under this type, weaving and merging movements are separated. It also provide an opporfunity to speed adjustment clear of the fieeway. When Freeway meets Freeway where traffic movement is heavy, interchange is provided with directional left tum in all four quadrants.
signs, signals and refuge for pedestrians.
2-20 Types of Interchange The tlpes and form of freeway intercharrge requires selection of the conformation that is best suited to a particular situation and demand. The functions of freeway interchanges are:
l. 2
To provide separation befween two or more traffic arteries. To facilitate the easy transfer of vehicles from one entry to the olher or betwesn local roadway and the freeway"
The simplest and low cost form of interchange is the diamond type. It is recornmended where the freeway crosses nonfreeway arterial. The cloverleaf type interchange is recommended for fi'eeway and arterial intersections. Intersecting arterjes are separated and free of intersections.
Y - Type lnterchanges
Objections to the Cloverleaf Interchange Design
l. It requires large area ofland. 2. At higher design speed, more time is consumed just to traverse the longer loops.
3.
Vehicles making left turn execute 270' iLdtrt. turn and travel greater distance beooming very unpleasant and
4.
Vehicles leaving the curve loop in one quadrant weave those entering the adjacent loop from the through road-
hazardous due to the sharp curyes and steep grades.
way.
Alternative cloverleaf design with collector distributor road recommended for one or two through street if the cost of added land paving and structures can be justified.
is
6b
FIGURE 2.27 TYPES OF FREEWAY INTERCHANGES
tt9
Elements of Roads and Highways
Deg the Highway
Directional Interchanges
Partial Cloverleal
Through freeway with rotary flyover with roundabout A Pollry on G.omctlic Dosign
FIGURE 2.28 TYPES OF FREEWAY INTERCHANGES
'to
FIGURE 2-29 CHANNELIZED INTERCT-.IANGES
71
I I
Deg the Highway
Elements of Roads and HighwaYs
l. 2. 3.
4" Four Level
For right angle intersections with linle trafhc. fie use of street sigh is more than sufficient. For Y intersection or other related conformation where vehicles meet at unfavorable angles may require channelization.
'lhe flared design will involve the following: a. Widening the entering trafEc lane to allow deceleration of tbe car and clear of through traffic. b. Widening the leaving lanes to provide acceleratiotr and merging fiom the traffic streams. Intersections must accornmodate large trucks. and the radius of all curves must be suffrcient enough to accommodate them.
A careful traffic count and projected future improvement must precede the design of all critical sections. Based from the dat.e gathered on trafftc count, the lane capacitl'could be determined including the ttumber of lanes to be constructed.
llll
)f_* Three Level
____)[ _
Three Level
FIGURE 2-30 FULLY DIRECTIONAL INTERCHANGES
whgre land is very expensive' Figure (a) Roadway at four levels is appropna]9 of roadways required to level 3, ln to**on (b) an
7-21 Highway Intersection at Grade at grade' highways except freeways have intersections connecting roads' lntersection area is considered part of every oocur' mov€ment turning In this area'all crossing and
Flared - T
Unchannelized - T
a)N I t
rHREE LEG rNrERSEcrroNs
| \
T- with Turning RoadwaY
All
FIGURE
2.31
INTERCHANGE AT GRADE
73
72
Elements of Roads and HighwaYs
Y - with Turning RoadwaYs
Deg the Highway
A
THREE LEG INTERSECTIONS
l\
AN* -=N T' \ /
ll /F- .' channerized-Y
Flared Type FOUR LEG INTERSECTIONS
Four leg channelized type intersections
tl /\
-AN-Four leg channelized type intersections
Rotary intersections roundabout
FIGURE 2-32 INTERSECTIONS AT GRADE
M
ulti-leg Intersections
FIGURE 2-33 INTERSECTIONS AT GRADE
Elements of Roads and l{ighways
Deg the Highway
2-22 Freeway Entrance and Lxit
TABLE 2.12 SAMPLING OF MINIMUM FOR FREEWAY ON AIID OFF TIIE RAMPS
The overall effectiveness of the individual freeway systems is governed by the flow characteristics of vehicles, and the driver's behavior near on and offthe channel.
On Ramp or OffRamp Design Speed Km/hr. Freeway
20
Speed
30
40
L = Length of Ramps in Meter
Km/hr. OnRamp
:
PARALLEL ENTRANCE
177
5l
450
303
174
ll5 147 170
95 t29 153
tO2 129
228 350
321
ll0
4't7
130 159 185
80 i,
150 273 400
95
Off
Ramps 80 95 110
189
48
68
Source: A Policy on Geometric Design
FIGURE 2-
34
DESIGN OF FREEWAY INTRANCES
,t' single lane on ramp vehicle flows into the outer continumg freeway lane. The design is either a taper blending into the through lane or an auxiliary lane parallel to the through lane. In either case, sufficient length is required to allow the vehicles to accelerate and merge into the ongolng vehicle stream at a speed near that of the freeway.
Vehicles leaving the freeway need distance to accelerate and clear of the flow of ongoing traffic. In situation where one lane could not meet the traffrc demand, two lane exits is necessary. In that situation, an auxiliary lane must be added to the freeway at least 800 meters before the point of exit. Even with one lane exit, an auxiliary lane is necessary for it reduces confusion and congestions. 76
5l
PARALLEL TYPE FREEWAY EXIT
TAPER TYPE FREEWAY EXIT
FIGURE 2-35 DESIGN OF FREEWAY EXIT
72
102
Elements of Roads and HighwaYs
2-23 Railroad
CTIAPTE
- Highway Separation
The main question asked on a railroad and highway separation is: 'Iilhere one is to go over- the railroad or the highway? If the highway is to go over the railroad, the structure itself is lighter *a *" highway load is much smaller than the railroad loads. With regards to the vertical clearance height, the railroad requires a minimum of 7.00 meters as against 4.80 meters clear distance above the highwaY. If the highway goes under the railroad, special provision is required for the removal of rainwater that falls wrthrn the^oppoiirrg area. If the ground water is high in the vicinity of the Lror.ittg, the roadway must be sealed against leakage and be made heavy enough to prevent from floating.
2-24 Bicycle Lane
soIL 3-1 Soil and its Origin From the earliest civilization up to the present time, soil is
the most important material that influenced mankind in his struggle for survival. The material where man grows his food, build his homes, roads, and ultimately his final destination.
The soil referred to in this study, is the materiat used to build with, or on that acts in combination with other forces of nature to make structures and land forms. The material classified under the field of Geotechnics.
Bicycle use is now becoming popular due to energy crises and traific problems. It requires separate road for the riders that is entirely separate from the vehicular traffic. The design speed is 20 to 30 kilometers per hoor for flat section. The width is 2.00 meters minimum for a 2-way travel. The grade of the lane is 57o maximum on short distances.
Soil may be defined as the accumulation of unconsolidated sediments and deposits of solid particles as a result of the rntegration of rocks. On the other hand rocks may be defined as natural aggregate of minerals connected by strong bonding of attractive forces classified as consolidated materials. Scientifically, most of the non-organic materials idelrtified as soil has originated from rocks as the parent material. Rock tlpes are classified into three major classes in accordance with their own origln or method of formations:
l. Igneous rock. 2. Sedimentary rock. 3. Metamorphic rock Igneous Rock is the result from the cooling and hardening of molten rock called magma ttrat has originated from deep
within the earth. The rapid cooling of molten magma called lava which was blown up by volcano solidifies into small crystal and 78
79
Blements of Roads and Highways Residual soil Transported soil
fine interlocking texture. The molten lavas that rapidly cooled on the earth surface are volcanic rock qpes called basalts, rhyolites and andesites. The molten rocks that were trapped deep below the surface of the earth, cooled slowly, and the mineral components forms into large interlocking crystals and coarse textured rocks classified as plutonic types of which,
Residual Soil or Sedimentary Soil is fomred from the weathering of rocks or accumulation of organic materials remained at the location of their origin. Weathenng plocess may
granite is the most common.
be attributed to ntechanical, chemical or solutictn weathering.
Sedimentary Rocks are formed from accumulated deposits of soil particles or remains of certain organisms that have harden by pressrue or cemsnt€d by materials. Sedimentary rocks include limestone and dolostone, shale, conglomerate and breccia. Shales are formed from deposited clay and silt particles. Sandstone is predominantly quartz cernented together with mostly silica, but sometimes with calcium carbonate of iron compounds. Conglomerate and breccia are similar to sandstone.
due
possesses
Mechanical weathering, refers to physical disintegration to effects of wind, rain, running water or tectonic forces
(earth quake).
Chemical and solution ieuthering, is deconrposition of rock due to chemical reactions that occur as a result of exposure to atmosphere, temperafure changes, reaction with water or other materials. l,ikewise. climate, topograplry, d'einage and vegetative cover have great rnfluences on the chemical or solution weathering process.
Metamorphic Rocks are rocks resulted from metamorphism due to changes in ternperature, pressure and plastic flow, changing the originai rock structure and mineral composition of the rock. Under tlds processes, limestone is change to marble, sandstone to quartzite, shale to slate or phylite
Transported Soils are frose rnaterials transported from their place of origin. Transportation may result due to the ef-
The process of rock changing to soil and soil to rock and alteration of rocks are continues and occurring simultaneously. The process of changes or alterations takes place over a long period of time, and there is no sst sequence wherein changes occtu.
The major categories of soils are gravel, send, silt and clay. Gravel and sand are universally known ts coarse grain soil be' cause of their individual particles that are large enough to distinguish without magnification. On the other hand, silt and clay are considered x fne grain soil because of their tiny particles.
There are numerous t]?es of rocks to elrumerate, but tlre construction industry and Engineer's concemed are not gsnerally afflueirt with the name of rocks but with their properties, specially in-place properties such as hardness, strength, durability, soundness and all other properties needed to build on or built wittr.
Particles larger than gravel are commonly referred to as cobbles or boulders. Thus, it is apparent that particles size alone is the basis of classifying sand, gravel, cobbles and boulders. On the other hand, fined grain soil is classified as either silt or clay not on the basis of particle size but on the plasticity or nonplasti city of the materials.
Categories of Soil
Over a var''lng range of moisture content, clay soil is plastic and sticky. When dried, possesses strong resistance to crushing. Silt soil has little or no plasticity and when dried has very little
Soil can be divided into two categories, namely:
fects of gravity, wind, water, glaciers of human
activif.
3-2 Types of Soil
8l
' f
Soil
Elements of Roads and llighways
l. Gravel Coarse sand 3. Fine sand
or no strength at all. If small amount of moist silt sample is shaken on the palm of the hand, water will appear on the surface of the sample but disappear when shaking stops. This phenomenon is called dilatancy. Sand mixed wittr silt is classified as silty sand, whereas, silt and clay mixture with mostly clay is called silty clay.
3-3 Characteristics of Soil Soil consists largely of minerals formed by disintegration or deconiposition of rocks. Disintegration or decomposition into soil may be caused by the action of water or other natural forces like temperature change, or by plant or animal life.
2.
4. Siltgrain 5. Clay 6. Colloidal claY
Gravel consist of rock fragments more or less rounded by water action or abrasion classified according to the following types:
a) b)
Quartz is the hardest of common rock forming mineral' IY'ell Rounded Pebbles and Boulders - those that undergone long period of wear that become almost quartz.
c)
Slightly Worm Gravel is rough and angular including other materials or rocks like granite, schist, basalt or limestone.
Soil contains humus and organic acids resulted from decay of vegetatron. All soils contain water, either free or absorbed in varying contents. Soil in most cases, are blend or mixture of particles of many sizes, shapes, and parsnt rock materials making its behavior very difficultto predict.
It is very common to encounter five to ten or more distinct types of soil along a kilometer of road. Change of soil types at frequent intervals has become a rule rather than exemption. Behavior of soil mass could be determined based on the characteristics of individual soil particles such as:
1.
2. 3.
Grain size Grain shape Surface texture and electrical surface charges, resulted from chemical composition and molecular structures.
Regardless of the differences in grain sizes as classified, tlre colrlrnon objective is to establish a basis for relating the particle size to soil behavior.
The General Characteristic and Classification cles are enumerated as follows: 82
of
soil
parti-
Fine Sand has particles that are more angular than the coarse and fine sand particles.
Coarse Sand is usually rounded like gravel with which
it
is
found and generally contains the same materials.
Silt Sand is similar to fine sand with the same mineral composition. They are found as rock flour in glacial moraines" It could be produced by chemical decay. Occasionally, silt contains:
1. 2 3.
Pumice Loess
Materials foreign to the associated sand.
The presence of silt in fine soil could be detected by its grittiness when small amount is bitten between the teeth.
Clay is plate like, scale like, or rod like in shape as a result of chemical weathering. Because of their smaller sizes, its performance is influenced by moisture and surface chemistry'
Colloidal clay is a finer clay particle that remains
pended in water and does not settle under the force of gravity'
sus-
Soil Elements of Roads and Matenials
If like soils occur under
like conditions of rnaterials" the
Coarse Grain Materials. F'or most purposes, coarse grain materials are considered satisfactory construction material. On the other hand, silty soil will create problerns in areas where the ground has moisture movement due to capillary action. Soil that contains clay would be troublesome, making the design and construction more difficult. As a rule of thumb, soil with clay
slope and weathering, the soil patterns or simiiar landfomrs, are also developed. The surface dramage patterns and erosion characteristics, together with the color of the goil, reflected the kinds and nature of the soil. Ridges with parallel axis may also reflect wind blown sand and silts.
should not be used clq:ser tn the roadway surfaces.
The texture classification of soil depending on the grain size distributron is classified irito three groups, namely: (a) sand (b) silt and (c) clay.
Irnpnrtant Graim Shape Characteristics
l. 2. 3. 4.
Rounded particles exlracted from the stream that has undergone wsar, are considered strong materials.
Flat and flaky particles that were not subjected to wear, are weak and variable that is not suitable for various used. Angular or roughly cubical shape particles produced from crushing strong and tough rocks, increases the resistance
of soil mass to deformation when subjected to load, due to individually interlocking grains. Generally, the rounded particle has the tendency to roll over each other when subjected to load.
3-4 Classification for Soils Pedology is the science of soils. It is the basis for pedological classification under the principle that: "like soil are developed on like slope when lilce materials are weathered in like " Regardless of geograplucal locations where slopes "fashion. and climate are the same, the depth and nature of soil mantle, are also similar.
Under the pedological classifications, soils that were produced in like fashion from the same parent rock, is assumed to possess siniilar engineering properties, that also requires similar enginlering trcatment. The number of sample to be subjected for sampling could be less than what is usually required. The test results serves as check on pedological classification contrary to the other classification methods that rely mostly on physical tests with little attention to pedological information. 84
GRADE Coarse Sand Fine sand Silty
SIZE OF PARTICLES (MM 2.00 0.25 0.25 0.05 0.05 0.005 Smaller than 0.005
-
-
FIGURE 3-1 TEXTURAL CLASSIFICATION FOR SUBGRADE $OIL OF SAND AND SMALLHR SIZES
Soil
Elements of Roads and Highways The posrtir:ns of every point inside the triangle represent the sieve analysis of soil in particular grading. After determining the grain size ofthe sample, charts is read as follows;
l. 2. 3.
2.
Sutrdivision of Snnd and Gravel Symbols
w
Spaces vertically upward startrng from zero at the bottom represent clay percentage.
GW SW
Spaces from left to right diagonally downward starting with zero at the left, represents silt. Spaces from right to left diagonally downward starting with zero at the right, represents sand.
Soil that is almost entirely a mixture of sand and silt are classified as loams. Every soil containing clay of less thmr 20o/o, is ctassified as loam with a prefix sandy or silty added to indicate which predominates. These will appear at the lower portion
C
for well graded, fairly clean materials fbr well graded gravel for well graded sand coarse materials with clay binder in combination GC and SC. poorly graded fairly clean material in combination GP and SP. coarse materials containing silts or rock
flour in combination GM and SM
3.
Fine grain soil (more than 50% ing No' 200 sieve)
4.
Fine grain soil grouped according to its liquid limit
of the chart
Soil containing 20 to 30 percent clay is called loam, with the term clay added to indicate the higher clay content. The name appears as loam classification in the chart. All other soil is designated as clay with prefixes of sandy, or silty to indicate the remainder of the materials.
Symbols
The Unified Soil Classification System, was introduced by the U.S. Anny Corps and the Bureau of Reclamations. Letters were used instead of numbers to designate the differerfi groups. The mechanical analysis and the liquid and plastic limit tests are the primary classification toois. The principal symbols and
For fine grain soil with liquid limit less than 50, low to medium compressibility in combination ML, CL and OL For fine grain soil with liquid limit greater than 50, high compressibility in combination MH and OH soil
soil designations are:
l.
Identification
For coarse grain soil - more than 50% relained on No. 200 sieves.
l\te lJnified Soil Classtfcation System recommended
sev-
eral ways for quick identification of fine grain portions of the soil, namely: For gravel or gravely soil For sand and sandy soil
l.
The sample is mixed with water to have a puttyJike consistency, then fonneci into pat and dried cornpletely 87
Elerments of Roads and l{ighways 2. 3.
5
6.
Soil
If the pat is hroken by the fingers and the dry strength is hrgh, plasticity of the sample rs considered high. If dry strenglh of the sample is high, then, it exhibits clay and colloid charactenstics If the sampie is a pat of fine silty sand, it rvill easily break in the finger. Fine sand will cause the pat to feel gritty on the fingers.and silts is smooth. Dilatancy or reaction to shaking is another way of classifuing the soil mortar. About one cubic inch of soil is rnixed with water and forrned into a pat of soft but ncrt sticky consistency. If the material is of fine sand, shaking and jotting ttre sample on the palm of the hand will bring water to the surface of the sample. Squeezing it between fingers causes the rnoisture to disappear. Silts react less cornpletely but clay does not.
TABLE
}I
3-5 Composition of Soil Soil deposit consists of solid particles and void spaces beparticles, either partially or completely filled with water. Void spaces not completely filled with water, are either filled with air or other gases. Therefore, soil deposits are composed of solid, liquid and gas
1y7esn
Engineers are interested to know the properties of soil deposit, specially, the strength and compressibility because they are necessary in determining the bearing capaclty and stabiltty of the foundation. Strength and compressibility of the soil is
directly related to:
l. 2. 3" 4.
Void ratio. Degree of saturation.
COMMON SIEVE TYPES AND F1ESH OPENINGS
Sisve Size
Designation No
U.S. Standard
Millimeter
Tyler Standard
Millimeter
Uritish Standard
Air=0
Millimeter
4
4.7N
8
2.362
10
1.651
20
0.833
40 60
o.u6
100
0.147
200
0.074
270
0"c)53
400
0.038
A Policy on Geometric Design
E .ol o
= G o F
Volume of Air = Va
AIR
Weight of tl
Source:
Soil density weight per unit volume. Water content of the soil.
Volume of voids = Vv
Weight of
water * l rw
Mass of
.?
o
water = Mw Weight of
solid
=
Ws
Mass of solid = Ms
t ,ffiIJ; ..:.
l,l'.,-u
o
'^;'.iiiTi ,.*. ,
(Soil) r.;
,;
F
Volume of Solid = Vs
iii,',,,,'it'iti ;i,ll
*'.;i-is$
FIGURE
o E
Volume of Water = Vw
WATER
ll
_'rld[3't*ffi
3.2 RELATIONSHIP BETWEEN VOLUME AND MASS WEIGHT
Relationship Between Mass Volume and Weight Volume From Figure 3-2,the total weight of the soil volume is:
l{ lJ
89
Soil
Elements of Roads and Highways Weight of the solid (Ws) + Weight of the water is equal to the Total weiglrt (Wt) or Ws
2.60 tD 2.75.
Similarly; for measurement of the mass'
The Unit Weight of Soil U could be Expressed as:
Ms + Mw: Total mass Ms*Mw=Mt
Wet unit weight Uwet
The total volume (Vt) = volume of solid
*
volume of voids.
Vt: Vs+(Vw+Va) = Volume of solid + Volume of voids Vt: Vs+Vv The relationship between the weight and volume of any materials will be:
Vg Dw
Where:
w- Weight of ttre material (solid, liquid or gas) V= G:
Uw=
M= Dw=
Dry unit weight Udry
Volume ocoupied bythe material. Specific gravity of the material. Unit weight of water at temperature stated (in most soil work, Uw = 62.4 pounds/ft3 9.80 dynes/cm3;or 9.81 kN/m3 regardless of temperature) Mass ofthe materials Density of water (l gm/cm3 or L95 slugs/ft3)
= ![s ( p/ft3, kN/-t) Vt
For soil density:
=
Wet destiny Dwet
ry[t_(
kghf,gm/cm3 )
Vt Dry density Ddry
= Ms (kglm3, grlcm) Vt
+l gm/cm3 = 62.4 polnds per cubic ft. The weight of one cnt' of water = 980 dynes The weight of one
VgUw
M:
= Wt ( p/ft3, LN*t ) Vt
Therefore, the total volume of the soil sample of the butk includes the solid and liquid air or gas. The volume of water and air is called-volume of vcids, Thus:
while Mass and Volume
The specific gravity of most commonly occurring rock or soil or soil materials is between 2.30 and 3.10.
* The specific gravity of soil solids lies within the range of
+Ww : Wt
W:
t
ft
of
water =
62-4lbs-
By definition, water content W is the ratio of tlre weight of water in soil volume to the weight of soil solids, or of the mass of water in a soil to the mass of solids. Thus:
W w o/o Ww Ws
Mw Ms
= Wwx 100% or Mwx
Ws
100%
Ms
Water content in Percer(age Weight of water Weight of dry soil Mass of water Mass of solid
Elements of Roads and l{ighways Soil
The relationship of water content and the r,veight r:f dry soil to the total wet weight of the soil volume should be:
Wt = Since:
Ws
p o/o
=
p%o
:
+Ww
Ww : (wolo)Ws r00%
By substitution: Wt
=
Ws + ( W% ) Ws 100%
Ws
e
O:IU*%J rc0%
ws= Ms=
Wt
Mt
t. q%
and the water content is known from a represertative sample.
The Void Ratio and Porosity in relation with the s,clid and void volume follows:
p%'.
The degree of saturation S, indicates the portion of the void in a soil material that is filled with water. The degree of saturation is expressed in percentage.
S7o=Vw
w
x 100%
Full saturation or 1007o saturation means that all voids are filled with liquid. Since
Vt = Vs * Vv and e = Vv
vt:vs*evs = (l+e)
Vs or;
Ys_= Vt
Vv
The Void Ratio is expressed in decimal number, and the Porosity P is conventionally expressed in percentage. Thus:
100%
spaces
Volume ofvoids Volume of solid
Vs
92
100%
1-
1+e
The weight of dry soil mass could be found easily with these equations when the weight of a large soil mass sample
e:
=
P%
pYo: e
t.iE%
rc0%
e :
100%
100%
100%
Simrlarll
Vv x Vt
And the relationship between void ratio and porosity is:
By Factonng:
Wt =
Volume of voids x l00o/o Total Volume
l+e
Example -1 One cubic foot of soil sample weighing 130 lbs. was taken from a test pit. The entire sample is thoroughly dried and finally weighted 120 lbs. Solve for the water content, wet unit
weight, and the dry unit weight. 93
Elements of Roads and Highways
q
.g
=lr
q tt
EEE
E (0
F
I
(v)
€N
.E
x-x 6.=6
E
:ro.9
xx odtx EE9 ooE t@
6
E (o
x6
x6.=
(a)
EI N
(\
do ar ZY
rl(,
=a 6P
*6 IJ
trJ
ze o(,
;) ;FAD {x
9F a> ut
cr)
x6
1r)
x 6 E tf,) (t
f
oo !to
L Z.o
+
8R
G
.9
o 6 (t
o
EEE
e*** zzz =
o
ilz EE
x6 E @o
xxx 66G
o
gE
t!
EE
AE Eto oct \b=
:9
#: i Etz' .g r
sg E.g
g!
E I!
E
lo
I
bo
Ha Eo c9
$iEe EEfE
;.E 5 Pd )(/)o
o
130
-
120
:
l0
lbs.
120lbs.
l30lbs/cu. ft.
gs3 !E3. S€E
:W:130: vt 1.0
Dry unit weight
Uory
= Ws =120
= l20lbs/cu.ft
Vt Watercontent wo/o
=E EeE
i6
water: Ww
Uwet
sFeI
gB
E s
: Weight of dry soil Ws : Weight of
Wstunitweight
66
E
x0t
Solution
i€+
*EE 9.9€
fo-
oQ, -> dF
}3
= 1.0 cu. ft.
E
E6
cD )c
FIGURE
Total volume of sample
E€
E Escr .^€ 6 oc, .l=0
E-
E
s
sEL E!d eE(' EoO oooc :'
.c
XX 6G
fa; €
:=g I o-9
o
ootrt lf,c.t-
arl
e t!
E9
EE
I
('?
F.
EE
tft -o .cl
-EE =-.9
.96
xx 6ad
iX .=G
(t
5gb
!t c 6 o
o
c') (\l
rEt € Et
-c EO J;ro iEo .D=
o
la)
o
trl Fl !e
E$fl
xx o6 EE
E
N
EE
F* Eg E.E 1
.lt g
6.=x FE6 o ttf
E tt)
:j
EEf
o
x6
c\l
,L
o o
c,)
(o
(J
F (,
o
EE
|rt
.a
CD
EEE € ON
E c) .E
I I
o
*
@
q
q,E
()P -g
-xx .=66
ut
5?
o
.E
E
F
o
v,
o
G'
CD
trl
5B
.9
BEE o@
iltrl
F
x
Soil
rr-iP
#Ei 8.gb
a.E 6
E3E
E 3a E g€ 5aL
= Ww x l00Yo = l0llbs. xI}}Yo
Ws
= Example
-
1.0
120lbs.
8.3%
2
Compute for the wet density, dry unit weighg void ratio, water content and the degree of saturation from a sample of moist soil with mass weight of 20 kg that occgpies a total volume of .008 cu. m. and .006 ou. m volume qf solid. The sample is dried in oven and weighted 18 kg. The specific gravity of the soil solid is 2.60.
Soil
Elements of Roads and Highways Example - 3
sample of wet soil has a mass
A 200 cubic centimeters
of
300 grams when 100% saturated. The mass was wheridried. Determine the dry density, dry unit weight, water content, void ratio, and specific gravity'
FIGURE
180 grams
34 trd = 3oo gm
Vt =
Solution
=
Wetdensity: Dwet Dry unit
H=ffi:2,500kg1m3
= Ws:Msq
U&y
:
200
Vt
FIGURE 3-5
Vt Solution
l8 kg. ( 9.81 kN/m3
). =
22.072kN/m3
Dry densitY: DdrY
.008m3
=
Ms
Vt Water content: w%o
=
=
20
-
Mrryx 100% Ms 18
l8 Void ratio:
180
x 100%o = I1.l%o
Dryunit weight: Udry
gn/cm3
= 56.Zlbs/cu ft
:
Water content: w % LMw) Ms
0.33
.006
300
S% : Wqs : 1l.l x2.60 =
e
0.90 gm/cm3
= ( 0'90gm/cm')6fats4'1)
e =Yv = .008 - .006
=
200 gm
Vs
Degree of saturation:
sm
0.33
sq-
x
100%
180 sm. 180 gm.
X
100%
87o/o
66.60Vo 97
Elements of Roads and Highways Volume of water.
Vw
=
Mw
gn*
= 3-Q0gn.--l-8ggn = l2o cm3
Soil Solution
l.
Since sample is saturated, all voids are filled with water.
(1.0X1.0 gmlcm') 2. Void
ratio: e = Vv = 0.40, but Vv
120 cm3 is the value of voids because 100% sao.ration means that, all voids are filled with water.
Therefore:
Voiume of soil solids:
Vs = Vt-Vv Vs : 200 cm'- l20cm'
= Voidratio:
-
:
e: Vv =f20 = 1.5 Vs 80
Vs*eVs 1.0 + 0.40
(1.0)
.Ww
:
80q = VsDw ( 80cm3X 1.Ogfi/cm3)
1.40
:
VwUw
):162'24lbs
(0.40)(62.4)
=
24.96lbs.
2.25
4
From which:
Laboratory test result showed that the v-oid ratio of a saturated soil sample is 0.40. The specific gruvity of soil solid is 2.50. Find the wet unit weight of the soil and its water content.
+Ww
=
Wt =
1d/5
wr =
187.20lbs.
162.24 + 24.96
Thus:
Wet unit weight:
I-Jwet
=
: oh Water content: w
Vs = 1.0
Wt
vt
= 187.2
133.7
= Ww x
1.40
pcf 100%
Ws
Assumed
= FIGURE 3-6
98
=
1"0( 2 60 X 62.4Pcf
Mg_.
= Example
Vt: :
Ws = VsgsUw
80 cm3
Specrfic gravity: gs :
and Vs are not known so. it is assumed that Vs = l 0
Vs
24.96Ibs. x 100% 162.24lbs.
=
75o/o
99
Soil Elements of Roads and Highways For soil above the water table but 10004 saturated. we have:
To relate a value given in grams per cubic centimeter (i.e. density) to pound per cubic foot (i.e. unit weight), multiply by 62.4 gn/cm3 = 62.4lbs/ft3.
Usuh
soil =
Usub
soil
=
Usat soil - Uw
Usatsoil- 62.4lbs./ft3
Submerged Soil
Exarnple - 5
For under water condition, the soil solid is buoyed up by pressrrs of the sugounding body of water. Therefore, the weight of srrbmerged suil, become lighter compared with the soil al-.ove water" Thus, the effective soil weight becomes the mit '*'eight when weighed rmder water. The weight of water in the voids of soil is zero when submerged, because all voids werc assumed to be filled with water, and the weight of the snlid is reduced bythe weight of water displaced.
One cubic foot undisturbed soil from a test pit, weighs 100 pounds net weight. The dry weiglrt of the sample is 80 lbs. What will be the effective unit weight of the soil if it is submerged below the ground water level when the specific gravity
Therefore. the submerged weight is equal to the soil weight above the water minus the weight of water displaced. Thus,
Wsub
=
Vs gs Uw
-
is 2.601
Solution U sub soil
:
Vs
(by faaoring)
Usub
soil
= &us = Vtotal
Vs Uw (es -1)
Vs(l+e)
= gg l Uw I *e
i00
= ll2
(100 pcO
=
50 lb/ft3
= Wf- : 80lbs. gs Uw 2.60(62.4) : 80 : Agff
Vv: Vt-Vs
For easy computation, the submerged weight is % the wst soil above the water table, except the soil containing significant decomposed vegetation or organic materials. U sub soil
1/z
162.24
Since the unit weight is the total weight divided by the total Volume, we have:
Usub-soil
=
Using the accurate formula, we have:
Vs gw Uw
= Vs Uw (gs - gw) = Vs Uw (gs-l)
YzlJwet
U wet soil (approximately)
=
1.0
-.49 = .5lff
e=Vv =.51 = I.04 Vs .49 Usub = ( gs - l) Uw = Q.6A-I\ rc2.4) (l + e) (l + 1.04) = 48.94lbs/cu. ft. or submerged weight: Wsub
=
=
(.49X62.4>(260-1)
Vs Uw (gs -
:
l)
48.921bs/cu. ft. t01
Elements of Roads and HighwaYs
Soil
or for the volume of one cubic foot:
For coarse grain soil, the higher the density or unit weight, the stronger the sheer strength, and the lesser the tendency to settlement by compression. Determination of In Place Density or Unit Weight is made on borrow pit soils to detennine the shrinkage volume or swell result as the soil is transported and compacted at the fill location. The standard practice is to test the in-place density of the soil after dumprng cn site, to determine whether, compaction is
Usub: Wsub : 48.92lbs./ft'
vt
1.0 ft3
3-6 Soit Reaction to DensitY The property of soil that contains larger amount of fines, are influenced by mixture railter than by any other factor. Soil that is strong enough with ing capability under one set of moisture is changed. Records revealed that an increase of l% moisture content on granular layers increase damages to pavernent by a factor of 700. Definitely, ';oils that are used as sub grade is subject to moisture changes. Density of soil is its mass per unit volume' It is sometimes expressed as "Wet Weight" or the total weight including water. The air volume in the soil substantially decreases as soil particles become dense when compacted. The most importarf ionsideration in pavement work is, to decrease the moisture (water) content ofthe coarse grain soil.
To decrease the moisture content, is to increase the density to improve the physical properties of the soil. High cornpaction of the sub-grade and base of the coarse grain materials is an accepted practice. On the other hand, over compaction of clay with high affinity of water, may result to big trouble unless confined by superimposed load like the weight of an over laying fill. This type of materials when compacted will mix on water and expand resulting to road surface failure'
necessary.
.
The modern equipment used for making in place density and unit weight test, is a nuclear apparatus. Through controlled use of n rclear materials, gamma iays (photons) are emitted into the tested soil. The photons collide wilh electrons in the soil materials. Some are being scattered and others were being absorbed. The quantity of, photons reaching a detection device relates to the soil density to determine the water content of the soil. A Newton etnitting device and detector is used.
3-8 Relative Densify For granular soil, the sheer strengtl and resistance to compression are related to the density of the soil. Higher strength and resistance to compression are developed by the soil when it is dense, or compact condition ftugh denstty), than when it is in
a loose condition (low density). ln a dense condition, the soil void ratio is low and high on loose condition. Relative densrty is expressed in percentage, thus:
Dro/o= emax-eo 3-7 In-Place Density and Unit Weight ln-place density, refers to the volumetric weiglrt expressed in pound per cubic foot, or kilo Newton per cubic meter, or *"gu gra-t per cubic meter of soil in the undisturbed condition or conipacted fill. The density of water is one rnega gram per cubic miter (l mglrn3) or 1.000,000 gm/m'. la2
:100%o
emrx-emin. Where: e max e
- Void ratio of the soil in its loosest
condition.
min - Void ratio of the soil in its densest condition. eo
- Void ratio of the soil in its natural conditioned or conditions in question. 103
Elenrents of Roads and Highways
Soil
so
Vv
03
Vs
.06
Dr%o=
:
0..5
emax-90 xl00% ernax*emin.
Loosestcondition Intermediatecondition Void ratio
=e
rru
Void ratio = eo
Densestcondition Void ratio = e 66
0.90
- 050 :80%
0.90
-
0.40
Dry unit weight of soil: FIGURE
}7
RELATIVE CONDITION OF A GRANULAR SOIL
Udry
In temrs of dry unit weight, the relative riensity is:
Dr 9/"
Wherc
:
Dul __Dq*
I -_l_
x
l00Yo
Dud
i
Dul = Dry unit weight in its loosest
= Do = Dud
condition. in its Dry unit weight densest condition Dry unit weight in its natural condition or condition in question.
TABLE
}3
-
6
of undisturbed fine sand .09 cubic foot, l0 lbs. dry weight with specific gravity (gs) of 2.60 was tested at the maximum density of 0.40 and minimum densrty with void ratio
A
sample
R.EPRESENTATTVE VALUES OF R.ET.ATTVE DENSITY
Dcscriptive
Relativc
Condition
Density %
Loose
Less
Medium Densc Dense
Example
lbs/ft3
Referring to table 3-4, the soil is dense.
l-l Do
: Ws = ,10lbs = lll wt .09
Very Dense
than 35
35-65 65-85 More than 85
Typical Rangc of Unit Wei LbV cu. ft. KN/m3 Less
than 90
90-
ilo
ll0 - 130 More than 130
than 14 14-17 17 -20
Less
More than 20
Source: Esscntials of Soil Mechanics and Foundation by David E. Mc Carthy
of 0.90. Find the relative density of the undisturbed sample. Solution
: Ws = 101b. = .06 ft3 gs Uw (2.60)(62.4) Vv =, Vt - Vs = .09 - .06 - .03ft3 Vs
104 105
Soil Test and SurveY Under the Stoke's Law, "The rate of settlement of solid through a given liquid or gas is proportional to the square of the diameters of the solid." The AASHTO method as specified is called Hydrometer Test AASHTO designation T-88.
CTIAPTER
SOIL TEST AI\D SURVEY
+l
Hydrometer Test
1. Samplc of the material ing
Test for Particle Size
Different soil has dif;lere,lrt charactenstics affecting the perof each individual soil by mois[re conteirt and density. There are sweral kinds of physrcal tests that have been dweloped to measure soil performance issued and recommeirded by AASHTO and ASTM. (See Transportation Materials Part I and II Tests or hferim Tests Methods by AASHTO). formance
The Sieve Analysis is the process being used to de0ermine particle sizes of gravel and fine aggregates. A sample of the the material is thoroughly dried and shake,n through series of sieves rangrng from roarse to fine. The amount on each sieve is weighed and recorded. The AASHTO standard sieve sizes for soil aggregates are presented as follows:
Sieve No. in Inches
By Number Opening in millimeter
) l t/2
3t4
37.5
25.0
r9.0
9.50
4.7 5
l0
40
200
2.0 .425 .075
Source: AASHTO Desien:tlon T-27,1v192 and ASTM Desig. E-l I
Material finer than No. 200 sieve (.075 mm) is not feasible in d*ermining the particle sizes. Insrtead, these are determined by observing the rate at which the grain5 settle through liquid or gas. 106
thoroughly with water and dispersing agent that dissipate any electrolytic bonds in the sample that might cause fl occulation and accelerate settlement.
2. After 12 hours, the miirture is agitated rnaking all particles suspended in water.
3. The mixture is then placed in a graduated flask, allowing 4. 5.
6.
the solid to ssttle under the pull of gravity.
The bigger particles settle first, followed by the smaller then the smallest one. The specific gravity of the liquid decreases. The changes are recorded by special hydrometer and read at prescribed intervals. Change in specific gravlty is related to the grain size of the material by Stoke's law' Careful control of temperature and other possible variable is strictly observed to obtain satisfactory test results'
4-2 Test to Evaluate the Effect of Moisture
3/8 4
50
No.10 sieve is mixed
Consistency of the soil varies from semi solid tlren, to liquid if water contsnt is increased.
l.
to
plastic
The Liquid Limit Test The AASHTO designafion T-89 onliquid
limit signifies the
percentage of moisture at which the sample changes- by decreasing the water from liquid to plastic state. When the sample is wet than the liquid limi! a grooved sample of the soil in will flow when lightly juned 25 times' On the other
"hand, "opif the sample is jarred at the liquid limit water separates
107
Elements of Roads and Highways
the soil particles just wide enough to rerncrvs ttre soil
Soil Test and Survey mass
shearing strength. Several tests on each sample are required to reach the moisture content wherein the groove in the sample is required to close at exactly 25 blows.
2. The Plastic Limit Test AASHTA Designation I-90 signifies the percentage of moisture wherein the sample changes with lowering w€firess from plastic to semi-solid condition. At this stage, the soil mortar starts to crumble when rolled into threads l/8" diameter" Additional water will make the soil plastic, but sands are nonplastic material that its non-plastic limit cannot be daermined.
3. The Plastic Index Text AASHTO Dengnation T- 91 is defined as the numerical difits liquid limit and its plastic limit. It is also referred to as the percentage of dry weight. ln some cornbination, it measures: ference bstween
a) The fineness and shapes ofthe soilparncles. b) The interplay of the attractive forces tending to hold the
c) d)
clay mineral flakes together. The thickness and velocity ofthe water film and, The quantity and electrical charges ofttre cations.
For coarse grain soil or fine grain soil with few particles of clay of colloidal size, small increase of water above the plastic limit will cause particles separation, destroying the athactive forces that provide shearing strength. It simply means that the difference between the plastic limit and the liquid limit is small, so that the plastic index is also small. On the contrary, for a soil that is high in clay or colloids, more water will be required before the attractive forces are overcome, and the strength of the mass is destroyed. In this case, the plasticity index is numerically high.
Experienced road builders use the Plastic Index as one conselecting the materials for under pavement. A common base course materials specified, requires the plastic index not to exceed 6 while others insist on not greater than 3. Soils with high plasticity indices are much less acceptable for sub-grade in
trol in
base course.
4. The Shrinkage Test Shrinkage test measures the changes in volume and weight that occur as partly mixture of, soil and water (except sieve No. 40). Sample is dried from the near liquid limit to constant weight of 110'C. The results are stated in of shrinkage limit, volurnetric change, and lineal shrinkage.
Higher value of shrinkage factor showed tlrat the soil will give more trouble and problem. The volume of a certain soil increases when it absorbs water. Soils that are suitable for subgrade and base course are those that oqpand very little when moistened. And those that swell more are considered as poor materials. A common soil specimen requires volume change limit of lYo for base coarse materials.
5. Hand Feel Test Experienced soil Engineer employ the "hand feel test" to approximately predict the plasticity index of the soil. The test may include
a)
Thread toughness at moisture content approximating tlre plastic limit.
b) c)
The air-dried strength.
Dilatancy
Soil mortar possessing hrgh plastic index threads and high strength without dilatancy.
will produce tough
r08 109
Soil Test and Survey
Elements of R'oads and HighwaYs On the other hand, soils having low Plastic Index (PI) will react in an opposite manner. Skilled soil technician could on tJre basis of this iest predict the Plastic lndex with standard error of about lToPercent.
clean sand with some rocks and certain other materials are classified as non-plastic materials because they cannot be rolled into threads as required in determining the plastic limit'
weight ofsoil per cubic foot cannot be termined in particular instance.
The Main Variables in the Soil Proper are:
l.
of the soil. Arnass composed of entirely spheres of one size in the deirsest possible condition will contain 75To solid and 25Yo voids. The smaller the sphere in the mass tlie higher the perce,lrtage of the solid" hence, particle size distribution may greatly affect
of road materials
Non-plastic soils are excellent lvpe
2.
when properly confined under wearing course' A weli gr"AtA rock dust form hard durable surface when
3.
6. Sand Equivalent
Test
AASHTO Designation T-176 is for field determination of the presence of undesirable quantities of clay-like materials in soil. Aggregate mixture is based on the volume, rather than on weight. Thi sand equivale,lrt is the ratio between tlre height of the-sand column (laboratory experiment tesQ and the combined height of sand and expanded saturated clay expressed in perg" Higher values of sand equivalent indicate superior ma"*t terials. The allowable moving avelage value from the Califomia Specification is 21 for sub base, 3l for agglegate baseand- 4^5Sb for aggregates of various type asphalt condete and 76 for concrete sand.
4-3 Density Test of Soil TheDensityofsoilorweightpercubicfootvarieswiththe
peculiarities of the soil itself, the moisttlre conten! and the compacted device plus the method of their use. The standard
ll0
densrty.
wst and comPacted.
Clean sand displace easily under load and their use as fill or base course create problems, but they may have other desirable feature such as facilitating sub-surface drainage'
Specrfc Gravity of the soil particles that may vary from 2.0 to 3 .3 that is normally between 2 .5 and 2.8 .
2. Particle Size distribution
As a rule:
1.
fixe4 but should be de-
3
.
Grain Shap" of Soil Particles . Sharp angular particles will resist shifting from loose to a compacted state. Flalcy particles in soil will decrease its density because they are difficuhto compact.
4-4 Laboratory Test for Soil Densrty Test for density may be divided into two:
l. Laboratory test to set $andard for density. 2. Field test to measure the density of soil in-placed on tlre roadway.
Laboratory tests may be subdivided into three, according to the basis of compaction procedures.
l.
2. 3.
Statictest. Dynamic or impacttest. Tamping foot or kneading compactiontest.
Static Test is determining the marimum density of soil sample in the laboratory. A sample of about 5000 grams of soil containing a specified percentage of water is placed in a cylinder mold 6 inches &.ameter and 8 inches high.
lll
Elements of Roads and Highways
Soil Test and Survey
The sample is then compressed under a load of 2000 pounds per square inch applied at the speed of 0.05 inch per minute. When the maximum load is reached, it is held for a period of I minute and therl gfadually released from the known dry weight of the soil. The mold diamet€r and the height dry densrty of the sample are comprrted. Several samples are compressed to delineate the peak of the moishre density. This peak value repre-
circle. About 25%. of the specimen is covered in each application. Compaction is through lsteadtng action in contrast with
seirts the standard.
Dynamic or Impaa fesf. Samples of soils each containing a designated perce,ntage of water are conrpacted in layers into molds of specified size. The sample is compacted by applying a number of blows from a free falling hammer of prescribed dimension and weight with flat circular face. The peak of moishrre densrty value represents the standard density. The AASHTO tests may be apptied on ttrat portion of the soil which will No. 4 siwe or all that es '/t" sieve. TABLE
4.I DETAIIS OF DYNAMIC COMPACTION N AASHTO
TestDaails Diameter of Mold (inches) Height of Sample (indreO Number of Lifts Blows per Lift Weight of }lammer lbs. Diameter Diameter of compacting Surfacr (inches) Surface Free Free fall tdistance (inches) Volume, Volume, rnet in cubic ft.
'AASIITO Designation
.
4-5 Field Density Test of Soil in Place Field density test is the means of comparing the density with the laboratory results. The comparison is performed on tlre basis of relative cornpaction defined as follows: Relative Compac,tion
=
Drvwt. /cu ft. of soilinlMtwayStructure Dry wt./ cu. ft. of soil sarnple at optimum moisture contsnt corpacted in standard mannel.
Relative compaction is the only measure by which the acceptability of a complaed roadway strudurc is measured.
Field Density and Moisture Content by Sampling TEST
The manners of determining relative compaction by samphng are as follows:
California
Standard
**Modified AASI{TO
Irpact
l.
Obtain samples of the compacted materials to be tested at
4to6
4to6
2.86
5 cut to 4.58
l0-12
full depth. Find the wet and dry weight of the sample, therL deter-
25 to 56
5 crr to 4.58 5 25 to 56
2.
20
3.
5.5
10
10
2
2
2
3
t2 1/30 or l/13.33
l8 ll30
18
or1113.33
T-99 ** AASIITO Designation
)
Varies
4. 5.
T-180
Tamping Foot or Kneading Compact Test. Tlrcmaterial is
fed into a rotating mold and compacted by several repetitive loads applied through tamping shoe shaped like a sector of the
t12
the static pressure or impact test
mine its moishrre content. Det€rmine tlre volume of sample in the fill by finding the weight of materials requred to fill the space. From the dry weight of the sample and the volume that it occupies in the fill, find the dw weight per cubic foot.
Find the relative compaction of the soil in fill by dividing its dry weight per cubic foot by the laboratory standard densfy.
There are four factors that affect the accuracy ofrneasuring relative density, they are:
1.
Change in the soil itself.
l13
Elements of Roads and Highways
Soil Test and Survey
2. The sampling methods. 3. The accuracy of laboratorytesting for standard density. 4. The accuracy of testing field density.
Load of test specimen at 0.1 in piston penetratiol
CRB = Load carried by standard crushed rocks based on 0.1 inch piston penetration
4-6 The Strength Test Soil tests to determine the strength of soil is classified into:
l.
Test for load carrying capacify, rate, and arnount ofconsolidation in soils that zupport the foundation. (This is applica,ble to bridge foundation).
2.
Test to measure the ing power of disturbed soils as compacted under standard procedures.
STEP - 1 COMPACT BY STATIC PRESSURE OR BY IMPACT
STEP.2 GRAPHANDFIND MAXIMUM DENSITY
California Bearing Rrtio Method (CBR) The Caffirnia Bearing Ratio Method (CBR) combines a load deformation test performed in the laboratory with an empirical desrgn chart to determine the thickness of pavement base and other layers. The tests are briefly conducted as follows: STEP
t. The disturbed soil samples at different moisture conteirt are compacted in 3 layers by static loading or impact hammer into a cylinder mold 6 inches diameter by 8 inches high. The specime,n depth is about 5 inches. The 5.5 pounds hammer AASI{TO standard density test is
.3
FIGURE
SOAK IN WATER
STEP
-4
APPLY LOAD
4.1 LABORATORY PROCEDURES IN FINDING CBR OF SOIL
The HVEEM Stabilometer Method
used in the rmpact method.
)
The moishrre deirsrty curve is plotted. The sample with greatest dry dens4y is chosen.
3.
The specirnen in the mold is immersed in water for four days to allow saturation. Expansion of the specimen is recorded.
4.
A small piston of 3 inches diamster is forced into the confined specimen. Load deformation data is recorded. The California Bearing Ratio is computed as follows:
This method measures the horizontal pressure developed in a short cylinder sample loaded vertically on its end. Stabilometer Operating Procedures
l. 2.
:
Four different samples are prepared on a short cylinder about 4 inches diameter by 2 % inches high of different known moisfure contents. Compaction is done using tamping foot or kneading compactor.
Soil Test and Survey
Elements of Roads and llighways
?,.
Each compacted specimen inside the mold is compressed until water exudes from it and several electric circuits wired in parallel through the base plate of the exudation measuring devices. ,-i|lrar'. r.- ,t?l(fxmfF4|;!F
e :rittli
t Head oftesting machine Follower for ap,plying load to specimen Neddle valve Air chamber
ldanually operated screw lype pump
Stabilometer T'est After the expansion test, the specimen is enclosed in a flexible sleeve and placed inside the stabilometer. vertical pressure is applied sl.rvly at speed of 0.05 inch per minute until it reaches 160 psi. The developed horizontal pressure is reduced to 5 psi using the displacement pump. The tums of displace_ ment pump needed to bring the horizontal pressure to 100 psi is determined. This displacement procedure ls intended to measure the penetration of the flexible cliaphragm into the intersection of the sample.
Liguid under small initial pressure Diaphragm Plate of testing machine
Loading piston Load cell leads
Cell pressure inlet
Sample cap
FIGURE
+2
DIAGRAM OF THE HVEEM STABILOMETER
Displacem ent transducer
It
was found out after several tests that soils in underlying of about 300 psi. It appears that soaking did not produce a condition of certain fine grain materials. ln effec! the exudation pressure is a different means in determining the moisture contents of the soil on the roadway. Moisture content in stabilometer test samples is set to bracket the 300 psi. value on which design was based.
After exudation test while sample is still in the mold, it is tested for expansion pressrue. A perforated brass plate is placed on the sample and covered with water for 16-20 hours. Expansion during this period is prevEnted, and the pressrue that prevents it is measured. As mentioned earlier, soils that expanded due to the presence of water should be placed under sufficient weight of fill to prevent swelling.
ll6
-
Clamps for displacement transducer
paveme,nts exceeded moisture under pressure
Test for Expansion Pressure
Porous stone Sample membrane
Samplo
be Vacuum inlet
FIGURE
+3
Chamber
Vaouum saturation inlet
Displacement transducer inlet
SCHEMATIC DIAGRAM OF DYNAMIC MODULUS TESTS
The resistance value R of the soil is computed by the following formula:
R:100-
100
2.5Pv-l+l Ph
Soil Test and Survey
Elements of Roads and HighwaYs Where:
It
R = Resistance value : Vertical pressure (160 psi) D = Turns displacement reading
Pv
Ph
:
(aPProx. from 2 to 5) Horizontal pressure in psi at Pv
was found that the modulus of asphalt concrete ranges depending upon the temperature. For cernent treated base, from 500,000 to 3,000,000 psi.. For aggregate base and sub base from 10,000 to 50,000 psi., and for fine grain aggregate soil, 1,500 to 50,000 psi, depending upon the water conlent. ,** r;
from 100,000 to 1,000,000 psi,
of 160 psi
Loading piston
Tri-Axial Design Method
Bearing plate
This method is used by some agencies for compression tests (see AASHTO Designation T-234). In open system tri-axial test, lateral pressure is held constant releasing from the container as increased load causes the sample to expand lalerally.
Transducer yoke
Lead to reoorder
Reaction and displacement continuously recorded
Constant supply of pressure
Displacement tran6ducet
Screw clamps to fasten yoke to sample
FIGURE
One of 3 tie rods
Lead to recotder
&5
SCHFMATIC DIAGRAM OF DIAMETRICAL TEST
Nuclear Devices Test
lmpervious bearing plate
-
Rubber membrane PerVious disk Lucile cylinder
FIGURE
4'{
TRIAXIAL TEST
FIGURE
+4
TRI-AXIAL TEST
Dynamic Modulus Re-compacted or undisturbed samples are tested to determine the influence of temperature, degree of saturation, density, and age on the d)'namic response of pavement rnatorials'
Recently, Nuclear Devices for determining in-place densities and moisture contents are used. The gauge readings are easily converted to density and prevent moisture using calibration curves or microprocessors. The portable device is either the transmission, or bac:< scatter tlpe.
The transmission type measures density and moisture content for any depth up to 25 centimeters. The back scatter device is placed directly on top ofthe soil layer or slightly above it to provide an air gap between the instrument and soil surface. It measures density and moisture content to a depth of 3 to 4 inches. Nuclear device overcomes construction delay where samples could be taken while construction equipment is operating. The Nuclear device travels over the fill at about 4.5 kilometers per hour and continuously recording the density and mois' ture content"
Soil T"est and Survey
Elements of Roads and Highways Gamma photon delector
lnstrum ent
Soil surface Transinrtted photon Compton scattered Photon
Gamma Photon source
FIGURE
4.6 SCI.iEMATIC DIAGRAM OF NI"'CLEAR DEVICES TRANSMISSION TYPE
l. Identification of soil types from: geological and agricultural soil maps, aerial photographs, and other sources. lnvestigation of ground water conditions, exarnining existrng roadway cuts and other excavations. Review of the design and construction procedures, and present condition ofroads that traverse the area. 4. Soil exploration along the right of way using auger boring and test pile. Sampling should be at fiequent intervals to fix the boundaries ofeach soil types. 5. Test holes should extend to a significant depth below the sub-grade elevation with reconnmended minimum depth. 6. Tlie location, nature of the ground, origin of parent materials, landform and agricultural soil name, should be re2.
corded. Gamma photon detector
Garn rna photon
7.
so tfce
Soil surface
8. Path of gamma photons (compton scattering)
Frcu RE
+7
scH
EIriJf.pJl?i#f;N
uc LEAR DEV| c Es
4-7 Soil Survey The preliminary soil investigation is an integral part of highway reconnaissance and preliminary location survey. In fixing the position of the roadway, the following should be taken into s: Soil conditions. Directness of the route Topograph5'
4. fught of way. 5. Neighborhood disruption. 6. Environmental consideration
The earlv phase of soil survey is the collection c'f infbrmation gathered from the following.
Each soil layer is described according to thickness, fixhrre structure, organic content, relation contents and cementation. The depth of seepage zones of fiee water table and bedrocks are also recorded. The soil profile along the roadway centerline showing location or test hole range of soil profile characteristics for each district soil gpe is plotted.
Along with the first reconnaissance and preliminary location survey. The highway agencies make a detailed study of the following data.
l.
The vertical and horizontal location ofthe proposed con-
2.
Location and evaluation of suitable borrow and construction materials. Need for the type of sub-grade or embankment foundation treatnent and drainage" Need for special excavation and dewatering techniques. Development of detailed sub-surface investigations for specific structures. lnvestigation of slope stabilrty in both outs and embark-
3. 4. 5. 6.
struction.
mem.
Elements of Roads and llighways
CHAPTER
Refraction Seismic Method
A
geophysical method used for sub-surface exploration cdled refraction seismic method relies on the principle that, the speed of shock travelling through the earth surface varies, depending upon the kind of materials. Shock waves travel through light loose soils at approximately 180 meters per second, and 6,000 meter per second on dense and solid rock.
ROAD MATERIALS 5-1 Aggregates Aggregates intended for either Bituminous (asphalt) or Portland cement concrete pavement, should be of good quality in accordance with the requirements of AASHTO standard or Item -703 of the Department of Public Works and Highways specifi-
If the earth's
crust is of uniform material for some d"pth, these time intervals are proportional to the distance from the origin of explosion. If the surface layer is of harder denser material, the time interval to a distant point is shortsned. The shock waves travel beneath the denser material along its upper margin, and then returned to the recording instrument.
cations which generally provides that:
"The aggregates shall consist ofhard durable particles or fragments of crusheri stone, crushed slag, or crushed rock or natural gravel."
The records frrr the time of wave travel against the shooting distance, the number and thickness of the different underlying layers, including the depth to bedrock can be predicted. This test is usefrrl in determining the depth of the rock but could be deceivrng on roughly tilted stratified materials.
Aggregates to be classified as good quality, must undergo various test enumerated as follows:
l. 2. 3. 4. 5. 6.
The refraction method was developed for exploration of underground conditions of roadway cuts. The shock wave is obtained by striking a 6 inches square steel plate wrth 4 kilogmms sledged hammer. The test is done by applying direct cur-
rent to flow through the soil between two other supply electrodes placed immediately at the third points. The resistivity changes where depth is produced, recording the results at vari-
Test for strength. Test for soundness. Test for affinity and swell. Test for shape and texture. Test for resistance to polishing. Degradation test.
Test for strength
ous electrode spacmg.
The criterion for aggregate stength test is the Los Angeles Rattler Test (AASHTO T-96) briefly conducted as follows:
This method is somewhat reliable although sometimes it can not be totally depended on regarding the information as to the presence of solid rock. It is useful in area exploration when it is used to find localized sand and gravel deposits.
1.
t22
Rattler test is done in a hollow cylinder closed at both ends. The cylinder measures 70 centimeters inside diameter by 50 centimeters long provided with steel shelf projectrng radially inward 3 % inches mounted with its axis horizontally on stub shaft a:rd fastened at the ends. 123
-L
Elernents of Roads and Flig,hwars
Road Materials The cylinder is rotated 500 revolutions at speed of 30 to 33 rounds per minute. 3.
After testing, the sample is ed on to No.l2
or strip's-off from the aggregate, the pavement will disintegrate sieve.
it
are sst aside, the amount of loss is the difference between the original and final weight expressed in percent. Those that es through
The FFIWA recommended that aggregates for a
5.
dense
graded mixture shall have 50 or less coefficient of wear.
For open graded mixture, the requirernent is 40 or less. However, percentage may be set in cases where excellent asgregates are abundantly available.
under traffrc.
Another reaction of the pavement is to pit when aggregates are pulled-off caused by running wheels. In the event that pavement mixture swells, the interlock and friction between the particles are destroyed resulting to collapse of the pavement stabiltty.
l. Hydrophilic is the term used when the
Test for Soundness of materials to deterioration from the effect of action like freezing and thawing. The comrnon test for soundness is the application q'ith sodium or Soundness refers to the resistance
magnesium sulfate. (
See
AASFIIO T -104
2.
).
l. A sample of fine or coarse aggregate is dried, and then, 2. 3. 4.
immersed in a saturated solution of sodium or magnesium sulfate, followed by draining, and oven dryrng.
The application of liquid solutions will cause splitting, crumbling, cracking or flaking of the particles surface. The application is conducted in five immersion and dry-
particle sizes. The result is recorded as percentage loss. Some road agencies do not require soundness test for aggregate intended for asphalt pavement particularly in areas where temperature of the pavement does not fall below freezing point.
Strong and durable pavement must have binder that adhere or stick firmly to the aggregate particles. If the binder separates
means fear, or against,water. If an aggregate is hydrophilic, the chemical bond between the aggregates and water is much stronger than those between aggregates and asphalt. On the contrary, if the aggregate is hydrophobic, pinholes will develop on the asphalt and water penetrate the surf;ace until it reaches the aggregates.
3.
Such water aggregate interferences may develop at the sharp edge of crushed particles and in due time, water
will 4.
ing cycles.
After washing and drying, aggregate samples are exermined carefirlly and sieve to determrne. the changes in the
Test for Affinify and Swell
t24
aggregate has
affinity for water than asphalt. Meaning, they like water than asphalt in contrast to hydrophobic which greater
5.
destroy the aggregate and asphalt bond. Sometimes, the stripped asphalt flushes to the surface of the pavement making it slicky, and after stripping, fine aggregates that are susceptible to swelling will expand when moistened, then disrupt the pavement Structure. The funmersion compression test (AASIilO T-165) indirectly measure the tendency of aggregate to strip or swell under the effects of water. The stripping problem of aggregate has long been perennial problem, although, many experienced engineers knows which of the aggregates being used will or will not be affected.
Shape and Texture of Aggregates
A relatively rounded smooth aggregate particles like natural gravel is recommenJed for Portland cement concrete pavement 125
Elements of Roads and Highways because the mixture is workable. Meaning, easily managed and consolidated inside the forms.
2.
The angular or cubical shape and rough surface texture aggrcgate tras been proven excellent material for asphalt pavement because it has stronger interlocking action and well adherence of asphalt binder to the particles.
3.
A thin or elongated piece of dirt is considered undesirable material for either asphalt or concrste pavement.
4.
The AASHTO Standard Specifications for asphalt pavement aggregate has no specific stipulation as to the control ofthe shape or surface texhrre.
Test for Resistance to Polishing
Road Materials
5.
Degradation Test Some aggregates degrade in the presence of water. This is measured tlrrough mechanical agitation in water under designation test T-210 of AASHTO.
l. Z.
One good cnterion for pavement desrgn is the high coefficient of friction between the tire and the road surface.
A good asphalt or
concrete road design is when "the rubber tire is in direct with the aggregate and not with the binder" measured under the following considerations:
1. 2. 3. 4.
t26
If in so short
About 2.5 kilograms of coarse aggregate that is retained on No. 4 sieve are washed thoroughly and agitated for l0 minutes. Sedimentation test like the sand equivalent test for soil is done on the sample ing the 0.075 mm (no. 200) particles generated .The durability index result ranges from 0
to
3. 4.
a time, the aggregate surface of the road be-
comes polished and sticky, the coefficient of friction between the road surface and the tire will be dangerously low. The skid resistance has bearing relation with the polishing of the agregate, prompting the road agency to consider the skid resistance measurement on existing road to be included and part of the road inventory. Aggregates produced from limestone are practically susceptible to polishing. On the other hand, if the parent rocks are sandstone or fine grain igneous type, polishing is not severe. Limestone coarse aggregate containing larger amount of sand that are insoluble in diluted hydrochloric acid, are found to be resistance to polishing.
Likewise, the friction factor between the tire and the road surface will increase substantially if silica sand is included in the mixture.
100, but the FHWA specifications set
a
minimum
valve of35.
For fine aggregate that es the 4.75 mm (no.4) sieve, test is the same as the above procedures except that the sample size is only ll2 kilogram. The sand equivalent test is performed after 10 minutes to establish durability Index of 35.
Particle Size
l.
For dense graded pavement.
-
The particle size of ag-
gregate ranges from coarse to dust.
2.
For open graded pavement. - One or more layer of the ofuniform size is used.
coarse rock
3.
For sheet asphalt. - The mineral aggregate is a carefully graded sand and mineral dust.
For aggregates, the inherent variance in the materials, the in sampling and testing, the segregation in the sample and in handling aggregate of large volume will mean that erosion
Blements of Roads and llighways
Road Materials
"the sieve analysis may nol be rhe true representative of the material actually incorporated. "
2.
Wren crushed aggregate is specified, not less than -50 mass percent of the particles retained on the 4.75 mm No. a) sieve shall have at least one fractured face.
5-2 Aggregate for Bituminous Pavement
3.
Generally" for bituminous or asphalt pavement, the aggregates constitute 88% to 96Yo by weight or more than 75o/o by volume. AASFITO standard specifications provides that:
The fraction ing the 0.75 mm (No.200) sieve should not be greater than 213 of the fraction ing the 0.425 mm (No.40) sieve.
4.
The fraction ing 0.425 mm (No.a0) sieve shall have a liquid limit not greater than 35 and a plasticity index. range of 4 to 9 when tested by AASF{TO 'I-89 and T-90
"The aggregates shall consist of hard, durable particles of fragments of stone or gravel and sand or other fine mineral particles free from vegetable matter and lumps or balls of clay and ctf such nature that it can be compacted readily to form a frm, slable layer. It shall conlbrm to the grading requirements shown in tcrble 5-l when te,sted bv AASHTO T-l I and 27".
Standard
Altemate
u,s. std.
MASS PERCENT ING Grading Grading Grading
A
Grading
c 100
100
5s-100 40-100 20-50 6-20
70-100
1u
100
100
t0
318
s0-85
5
No.4
35-65
2
No. 10
25-50
60-100 50-85 40-70
0.5
No.40
I 5-30
2545
0.075
N0.200
5-20
5-20
Pavement
tion ofthese three.
B
25
5-3 Aggregate for Portland Cement Concrete In order to obtain high quality concrete, road a,qencies liave imposed almost without exception that all aggregates shall appropriate tests for strength, soundness, wear or the combina-
TABI,E 5-1 GRADING REQUIREMENTS SIEVE DESIGNATION
respectively
l.
non-hardening of the concrete. Under AASF{TO T-21 standard test, the aggregate is treated with a mixture cf sodium hydrochloride solution, and when the treated aggregate turns dark, organic materials are said to be present in the aggregate.
55-100
30-70 8-25
2.
The strength of fine aggregate is measured pression tests of sand-cement mortar.
J.
Soundness
aggregate is measured by the resistance
deterioration under the action of Sodium or N4agnesium Sulfate. The sodium sulfate test is five cycles. The maximum loss under AASHTO specification is l0%.
DPWH standard specifications. Coarse aggregate materials retained on 2.00 mm No.lO sieve shall have a mass percent of wear by the Los Angeles Abrasion Test (AASHT T-96) of not more than 45
offine
by the com-
to
The following materials are classified under item 300 of the
l.
The presence of organic impurities in the aggregates intended for concreting road pavement may cause slow or
4.
For Coarse aggregate the requirement consists of crushed stone, gravel, blast fumace, slag, or approved inert materials of similar characteristics or combination thercof
Elements of Roads and Highways
Road Materials
having hard, strong durable pieces free from adherent a
coatrngs.
bo C)
AASHTO Fine Aggregate grading By Weight Percent ing
a
sieve No. 4 sieve No. 16 sieve No. 50 sieve No. 100 sieve
z
trl
F
tsl
100
& (J
95- 100
o U I
318"
I
n
c'.
u)
oo
60
z
45-80
t0-30 2-10
tr trl F
a q;)
a.l
{
&
AASHTO M-80 (a
/ Materials
Pavements
Bridge Deck
u h
Chert (2.40 speciflc gravity ) Coal and Lignite
3.0% 0.5
rOO
or t--n AA .+
c.l
3.0
Materials ing No. 200 sieve
1.0
o trl
Sodium Sulfate Soundness
12
Magnesium Sulfate
18
I
a a
ooXn OT dcq
F rr)
ftl
o|.
o
oooo r)o o\
c\l
o o.l
e5
FI Fl Fl
o
t? ra trl
The Department of Public Works and highways Standard classi$ aggregate under item 703 and specificalll'provides that: Specificatio"ns
l.
Aggregate shall consist of hard, durable particles or fragments of crushed stone, crush slug or crushed or natural gravel. Material that breaks up when alternately wstted and dried shall be discarded.
6l
c)
oo
o
E9
o\
r.q 5b4 bQo
6
*z 6d
k
+R N= -'A
F-bhghe..,
Fl tn Fr
'.= t'l
s; :f
c.l oo
I(.)
co
o
z
Clay Lumps
a '5
oSRn. 9; dd:
FJ oo
a) bt)
.ir
r)
Roo :\ocoh
B &
,r,,4
c.l
LJ
tsl
I I
fL
dc\
c?)
TABLE 5.2 MAXIMI]M AMOI]NT OF'DELETERIOUS MATERIALS PERMITTED IN COARSE AGGREGATES FOR CONCRETE
tt rnc)orr|
AhOO
G)
a h
+t
ou 6qr
3
.,. o X-
?o.,; HEa Y€\
SSsV\l A:.;;A
zZzZziE
$-s !€es€T: et--fui\i. T,colT
= b6: 'aY,
a\ r:= o 7a
vc:
Ji'O
*
29,C lctO
i+it
Road Materials
Elenrents of Roads and Highrvays
2.
3.
Coarse Aggregate is the matcrial rctained on the 2 00 rnm (No.l0) sieve and shall have a percentage of rvater not more than 50 for sub-base and not more than 45 for base and surface courses as detennined bv AASHTO designation test T-96.
Fine Aggregate is the material ing the No.l0 sieve (2.00 mm) consisting of natural, cnrshed sand, and fine mineral particles. The .fraction Ttcsssit'tg the t).075 rnm (No.200) sieve should not be greater than 0.66 (.213) ot
l-he DPWH Standard Specifications relative to mineral filler states that:
"Mineral./iller shall consist off nely divided mineral matter cr"' rock dust, slag dust, hydrated lime, hydraulic cement, ash or other suitahle rnineral matter. It shall be free from fly organic impurities and at the time of use shall be sfficiently dry to flow .freel1, and shal.l be es,yentially free from agglomerations " such
AASHTO M -17 provides that:
the fraction ing the 0.425nun (No.40) sieve.
e,
Percentagc ing try'weight shall bc as follows:
For Base Course, the fraction ing the 0.425 mm No.a0) sieve shall have a liquid limit of not more than 25 and a plastic Index (Pl) not greater than 6. For sub-base course. the liquid limit should not be greater than 35, and
No. 30(0.66mm) sieve 50 No. 50(0 30rnm) sieve 95-100 No. 200(0"075mm) sieve 70-100
Plastrc lndex not greater than 12.
5.
For Surface Coarse the fraction ing the 0.425 mm (No. 40 ) sieve shall have a liquid limit not more than 35
AASI{TO fiirtlier stipulates that all minerals other than hydrated lime or Portland cernent, the Plastic lndex (PI) value shali be 4 or less.
and Plasticity Index not less than 4 nor exceed 9.
5-4 Mineral
filler
The strcngth of road pavement r.vill be increased if dust additives which dense the graded mixture is added. It is called mineral filler that redrrces the void contents in the mixture. This dust additive is not the ordinary dust that is being found in our
floor or tables.
5-5 Bituminous Material Bituminous material or Asphalt in short, is a viscous liquid used as binder for aggregates in road construction. At normal temperature, asphalt is either slightly thicker than water or hard but brittle material that breaks under a hammer blow when cold.
l.
Dust additive is classified into:
l. l. 3. 4 5. (t
Finel-v porvdered limestone Slag
Hydrated Linre Portland Cement
Trap rock dust Flv ash
2.
Bituminous material
is in liquid form when mixed or
cornbined with aggregates. This liquid form may be produced either by heating the hard asphalt, by dissolving in solvernt or by emulsi$'ing in water. However, there are bituminous liquid materials available and read-v for use. The action of asphalt binder depends on its tvpe and the aggregate it is combined rvith. The purpose of the asphalt binder is to resist the abr;rsive force brousht about bi,
heaw traffic.
r Road Materials
Elernents of Roads and Highways TABLE 5-4 SUGGESTED SPRAYING AND MIXING TEMP. ('C ) FOR BITUMINOUS MATERIALS AND ROAD TARS T+
3.
Surface Temp.
Type and Grade of Asphalt Asphalt Cement 15-140 120-145 120-155 130-165 130-170 105-135 135-165 135-165
80-120 80-120
AR-8000 AR-16000
13t165
80-'t20 80-120
20G30O pen.
1
AC-z.5
AC-5 AC-10 AC-20 AC-40 AR-100t)
AR-2000 AR-4000
12&150
8$100 60-70 4G50
1
150-175 15-150 120-155 120-165 1 30-1 70 130-175
Cutback Asphalt (RC,SC) 30 ( MC onV ) MC. 70
i
i
ss-1 , css-1
ss-1h, css-1h
RT10-'11-12
80-120 80-120 80-120 EO-120
80-120
80-120
80-120 80-120
80-120 80-'t2o
-
130+ 130+ 140+ 145+ 150+
30+ 50+
75+ 95+ 110 +
5G80 10-70 10-70 10-70 10-70
$ $ $
20-70 20-70
$
20-70
required.
5-6 Bituminous Binders Asphalt cement is used as binder for almost atl high types of bituminous pavement. Asphalt cerirent is a semi solid hyfuocarbon retained after fuel iurd lubricating oils are removed from petroleum. The softest grade r.lsed for pavement is the 200-300 penetration. The 60-70 penetrations is the hardest type.
Penetration refers to the consistencies of asphalt cement as described under AASHTO-T49. It is the distance that a standard needle penetrates a sample under known conditions of loading time and temperature. Recently, the procedure used in grading asphalt cement is the Viscosity Test rather than the Penetration Test. (see AASFIIO M-226 Specification for Transportation Materials).
6S.105 8S.120
Cutback or Liquid Asphalt
'l.
2S70
1+55
15.55
2765
27€5
65-105 80-120
6t105 8G120
Source: Asphalt tnstitute for Asphallic Materials AASHTO Guide Specs for Tars. + oF=g/soc +32 $ Temp. of the emulsified asphalt in the pugmill mixture. Rapid curing RC grades are not recommended for hot pugmill mking Max. Temp. asphalt cement and cutback asphalt shall be below thal at which fogging occurs.
ii "
road pavement is the open t1pe, consisting entirely of coarse particles and asphalt, heavy binder is needed requiring rnore asphalts. On the other hand, if aggregates in the pavemert contain fine particles, cohesion will be developed by surface tension in the thin asphalt film surrounding the fine particles. Hence, less viscous asphalt is
2S60
Road Tars RT1-2-3 RT$.6
RT7€-9
80-120
20+ 4.O+ 55+
250 800 3000 Emulsified Asphalt RS-l, CRS-1 RS-2, CRS-2 MS-1, MS-z, CMS-2 MS-2h, cMs-2h
130 + 140 + 140 + 145 + 150 + 135 + 140 + 145 + 145 +
If
2.
Liquid asphalt is a petroleum product consisting of asphalt cement with a liquid distillate (diesel, kerosene or gasoline). The less viscous asphalt contains diluents as little as l5%. The use of cutback is being frowned for two reasons: a. It is a usable fuel b. It is an air pollutant. Cutback or liquid asphalt is classified into: Slow curing (SC) road soil Medium curing (MC) cutback asphalt Rapid Curing (RC) cutback asphalt
Road Materials
Elements of Roads and Highways I
Emulsified Asphalt Emulsified asphalt is a kind of mixture wherein the mtnute globules of asphalt disperses in water. Asphalt contsnt ranges fram 55o/o-70% by weight. Emulsion could be applied or mixed at norrnal temperature, because when the water content evaporates, the asphalt remains. It has the following characteristics.
l.
Emulsifed asphalt is excellent with wet aggregate because the water medium carries the asphalt into a superior with the particle surfaces.
2.
is an altemate tc cutback asphalt for energ-v and environmental objectives. It is an effective material in coating electropositive aggregate such as linu:stone but tend to strip from aggregates with high content of silica for having strong elqctronegative sulface
Emutrsi-fied asphalt
charges.
3.
T\e Cctionic Emulsictn is very effective on high siliceous agg,regates but may strip from high alkaline that carry
The AASHTO classification of coal tars includes RT-l to RT-12 and RCTB-s to RTCB-6.
RT-l is
Rejuvenating Agent is an emulsified petroleum resin sprayed over the surface of an old asphalt road that changes to asphaltenes causing the binder to harden and cracks. The rejuvenating agent sprayed over the pavement and softening the binder. Too much application however, produces a slick pavement surface.
Oxidized Asphalt and Road Tar Oxidized asphalt is suitable only for roofing and similar applications. Highway used of oxidized asphalt is limited to water proofing of structures and filling ts of concrete pavement. Road tar is a by-product of the distillation process of coal. T'ars are produced from gashouse coal tar, cook oven tars and water gas tar. t.r6
of Prime
Cloat at
normal temperature.
The DPWH Specifications Classify Bituminous Tack Under Item 302 which provides that:
1. 2. 3.
Bituminous materials shall be either Rapid Curing Cut Back or Emulsified asphalt. Tack Coat shall be applied only to dry surfaces or slightly moist. No Tack Coat shall be applied when the weather is either foggy or rainy. Immediately prior to the application of Tack Coat, the road surf,ace is lightly sprayed with water, but not to be saturated.
4.
strong positive surface changes.
4"
suitable for application as Tack
5.
The rate of application of either the Rapid Curing, Cut Back or Emulsified asphalt is within the range of 0.2 to 0.7 liter per square meter. Any excess of this specified quantity should be blotted by sand or removed. Tack Coat shall be sprayed only as far in advance on the surface course as will permit it to dry in a tacky condition. Traffic shall be kept off the Tack Coat until after firlly dried.
Bitumen
-
Rubber Mixture
The bitumen rubber mixture for road pavement was experimented in Holland in the year 7929. It was adopted in the United States in 1947 and later, in European countries' The assessments of the road states that:
l.
Very little improvement gained as far as coefficient of friction on newly laid pavement but expect higher advantages after six months. The analysis of the Bureau of Public Roads states tlat:
t37
Road Materials
Elements of Roads and Highways
"An appraisal of the real economic value of the addition of rubber to asphalt must wait on further observation of the
for demulsibility b. Test for settlement a. Test
behqvior of experimental pavements uhder the influence of age, weather and
2.
Sieve test
trffic".
d. Cement mixing test
Particle charge and PH tests f. Miscibility and freezing test
According to the report, powdered rubber foams added to bitumen has improved the stability of some but not all.
5-7 Problems Associated with Bituminous
Epoxy Resin as Binders
Binders
Epoxy binders are produced in a clear, dark, rigid and flexible form for application to either concrete or asphalt pavement. Hardening can be auained by mixing the resin and the catalyst hardener prior to application. The result is called thermosetting. Meaning, it will not soften under the influence of heat or the action of solvent like water or petroleum products. The high cost of resin has restricted its use to bridge surfacing and other
l.
The thickness of asphatt film in the pavement, ranges from .005 to .010 mm. Test result showed that the thicker the asphalt film, the lesser is the process of aging. Where pavement has lower percentage of voids, aging is also
special non-skid seal coating surface only.
2. 3.
Test for Bituminous Binders
4.
l.
turely. One example is mixing asphalt with an overheated
Test of consistencv is subdivided into:
a. Kinematics Viscosity test AASFIIO T-202 b. Saybolt-Fural test AASFilO T-72 c. Engler specific gravity test AASFITO T 54 d. The float test e. Penetration test
f.
Softening point
test
AASFITO T-50 AASF{TO T-49 AASI-[[O T-53
2. Test for durability AASlffO T-52 3. Test for solubility AASFrrO T-44 4. Distillation test AASF{TO T-78 5. Thin film oventest AASHTO T-179 6. Flashpoint AASFilO T-48%79 7. Test for homogeneity of petroleum asphalt AASHTO 102 8. Special test for Emulsion asphalt AASHTO T-59 138
relatively low. Mixtures that are too dry, cracks and breaks easily. Higher asphalt content and lower percentage of voids may cause instability of the pavement. Improper construction procedures can age asphait prema-
5. 6. 7. 8.
aggregate.
Storing the mixed materials, or an extended period of mixing, the temperature produces substantial reduction of asphalt penetration.
Climatic conditions can seriously affect the behavior of asphalt binders.
Different brand or source has variability in behavior. The viscosity of some asphalt varies with temperature from that of the others. An asphalt meeting a specified penetration requirement at 77'F but with hrgh viscosity temperature ratio will become hard and brittle at lower temperature.
5-8 Bituminous Pavement The bituminous pavement
is a
combination of mineral ag-
t39
Elements of R.oads and Higtrw*ys gregate and binders. 'lhe mixture of rock material particles with asphalt has created so many natnes to wrt:
L Asphalt macadam Asphaltic concrete a Mastic 4. National paving 5. Plant mix 2
6. Asphalt sheet 7. Road mix 8. Armor coat
Road Materials
l. 2.
9. Oil mat etc.
Although several names were afrxed to bituminous pavement, yct, there is only ane thing to that, all bituminous roadways are nothing more than a mixture of mineral aggre,gates and asphalt. Meaning, asphalt road is virtually o Bituminous Rosd
3.
Viscous asphalt binder is heated to a fluid condition and mixed with heated aggregates. The mixture is then laid and compacted while still hot. Mixing liquid or emulsion asphalt with aggregates at normal temperature is either by plant or road mixing. The mixture is laid and compacted at normal temperature before the solvent evaporates or the emulsion breaks. Spread and compact the clean crushed stones, sprayed with heated or emulsified asphalt binder over it. Cover the sprayed pavement with fine aggregate. This process is referred to as the "penetrotion metltod."
5-9 Asphalt Concrete Pavement Qualities of Asphalt Road To consider an asphalt road in good service, it must posses in its full life the following qualities:
l. 2. 3. 4. 5.
The surface must be free from cracks or raveling due to shrinkage and fatigue failure. It mpst withstand weather condition, including the effect of surface water, heat, cold and oxidation. It must be resistant to internal moisture such as water vapor. It must posses a tight or porous impermeabie surface as the case may be suitable to underlying base on sub-base. It must be smooth riding and skid free surface.
The term Asphalt Concrete refers to a dense graded road surface made of hot mineral aggregates, mixed with hot asphalt and laid at high ternperature of about 275'F to 300'F. Asphalt concrete is the highest type of dense bituminous pavement suitable for the most heavily traveled roads. A prime coat is first applied over untreated and treated base before asphalt concrete is laid. The purpose is to bind any loose particles of the base and likewise act as bond between the base and the pavement to deter rising moisture from penetrating the pavement. The thickness of compacted asphalt concrete ranges from 2 inches for lightly traveled road to 6 inches or more for roads where traffic is considerably heavy.
5-10 Bituminous Pavement Failure The success of an asphalt pavement lies or depends on the construction qualrty of the sub-grade, and the base course. On the contrary, pavement failure would be considered as a foregone conclusion.
A satisfactory asphalt pavement could be attained under the following construction procedures :
Bituminous pavement failures are caused by excessive load. Heavy load creates deflection on the road surface, with insufficient underlying strength. Repetitious application of excessive load will roughen and crack the road pavement that ultimately result to complete failure of the roadway. Deflection on the road surface may be the effect of elastic deformation from the consolidation of the base and subsoil or from the combination of
140
t4l
Elements of Roads and Highways
Road Materials
elastic and plastic def,ormation. Repeated healy wheel load on highly resilient soil causes deflection leading to fatigue failure of the asphalt surface. Alligator or map cracking of the surface will be substantially evident. Elastic detbrmations in the subgrade penetrate to a depth of 6.00 meters although mostly to a depth from the surface.
Tire load
Tire load
--_-.,
I
Upheaval of surface and base
1. Surface Failure
FIGURE
2. Base
Failure
3. Basement Failure
5.1 PLASTIC DEFORMATION OF SURFACE BASE & SUBGRADE
Constructing the Macadam Asphalt Road
l.
Spread tlre coarsest aggregate to the roadway. Compact with either smooth wheeled roller or vibratory devices. 2. Smoothness of the surface is checked after compaction. Low spots are corrected by removing, replacing and recompacting the stones until smooth surface is attained. J. Apply asphalt by spreading the right amount of bitumen at specified temperature. The lower stone layer will not be coated if the asphalt binder is too thick. On the other hand, too fluid mixture will cause running of the binder down the underlying layers. 4. In placing the keystone base course, sufficient amount of smaller stone is mixed and spread on top to fill the interlocking voids, followed by compaction then spraying with
5. 6. 7.
5-11 Macadam Asphalt Mat Bituminous macadam road has large amount of voids in the lower part of the aggregate layers. The road strength originates from the interlocking aggregates that hold the individual stone together. Under this condition, a strong well drain base that will not squeeze upward into the pavement voids is required.
The Bituminous Macadam base or surface is composed of two or three layers of progressively smaller, clean, sharp angular stones bonded by asphalt. Each layer is compacted by rolling then sprayed with asphalt. Usually, the surface course is sealed by spraying a binder and blotted with fine crushed stones. The binder at the time of spraying is fluid enough to penetrate and coat the aggr egate particles. 142
asphalt binder.
Sealing of the surface is applied to seal the paveme,nt against moisture. These involve spreading of selected binder, spraying and rolling of the cover aggregates. During construction, the weather must be dry and warm. If not it is better to used emulsified asphalt as binder. Before the application of asphalt binder, coarse aggregate is first chocked with smaller stone to seal the remaining top voids, followed by spraying emulsified asphalt binder.
5-12 Surface Treatment Road surface treatnent method is applied to upgrade untreated surface and to rejuvenate an existing pavement. The inverted penetration method is applied wherein the binder asphalt is first prayed over a prepared surface then covered with fine aggregates. This procedure is in contrast with the penetration method wherein the spraying of asphalt binder is done after the placement of the aggregates.
On the basis of pu{pose to be accomplished, surface treatment is subdivided as follows:
143
Road Materials
Elements of Roads and llighwaYs
l. 2. 3. 4. 5. 6. 7. 8.
Dust palliatives to control dust.
Prime coat or tack coat treating the surface to provide new wearing coarse. Armor coats to provide protection for untreated surfaces. Seal coats and retreads. Sheet asphalts. Tack coats.
Slurry seals. Asphalt overlay.
The lighter medium curing cutback oil is generally used for prime coats. It is fluid enough to penetrate into the base course Lut retain viscous asphalt in the purses of the treated surface. Surface to be applied with prime coat binder, should be uniform without variations, properly shaped, moistened and rolled to have a plain uniform and solid surface-
Light tars grade RT-l to Rt-3 have been successfully used as prime coat. The amount of asphalt binder to be applied is from 0.3 to 0.8 gallons per square meter surface area dependrng
Dust Palliative
upon the tightness of the surf;ace to be primed.
Dust Palliative is a surface treatment or application of asphalt to control dust and fine sand along the highway.
After the application of prime coa! vehicular traffic should be detoured until after the surf;ace is no longer sticky. lf traffic detour is not possible, a blotter ofcoarse sand shouldbe applied
l.
2. 3. 4.
The road surface is treated with the application of about 0.2 gallon per square meter of lighLt slow curing oil. The material commonly used is the MC-70 but occasionally the MC-30 or the MC-70. This oil penetrutes the surface to about % nch and provides film that surrounds the particles and bind together. Slow curing oil is usually selected because it remains soft and last for quit longer period of time. Satisfactory result was also noticed when slow setting emulsions diluted in a mixture of 4 to 9 parts of water was used. Cut-back or Emulsion asphalt is unsatisfactory material for surface treatment as dust palliative. It becomes harder asphalts producing brittle surface that easily cracks in a short time followed by fast disintegration. Used crankcase motor oil is also considered as an effective dust palliative.
Purpose of the Prime Coat or Tack Coat.
l. 2. 144
To plug the capillary voids in the pavement in order to Stop the upward movement of moisture. ^fo improve adhesion between the base and surface course.
on top of the prime coat.
Armor Coat Armor coat is a surface treatment using a thin bituminous binder covered by mineral aggregate applied to an earth, gravel or water bound macadam surface or to stabilize the base' Surface treatment applied in two or more lifts is referred to as armor coats. When fund is limited, ,umor coat is used as temporary pavement and protection of the base materials.
l. 2. 3.
For two-course treatment' the maximum size of cover mao/o terials for the first lift is to I inch. For three treatments, the maximum size of aggregate cover is
l" tD l-Il4
inches.
The maximum size of aggregate for each subsequent lift should be reduced.
The surface treatnent, that follows the prime coat, could be $ as thin as % inch, or as thick as one inch. The thinner type 0'40 sometimes called, one shot type consisting of about 0'20 to 145
Elements of Roads and Highways
Road Materials
gallons per square meter of ailf, neavy liquid asphalt materials covered with 5 to l0 kilograms of clean,ir""n"d stone, or fine screened gravel, or slag which are free of dust. Larger cover
materials with maximum size up to yz,, or 5/g,, will require 15 to 20 kilograms per squ:ue meter surface area. Surface treafinent is applied on a clean, and dry surface, no wrnd and in good weather condition. For healy traific highway,
surface treatnent only serve as pailiative for sustain the traffic load.
it lack ,t
"igth
io
Seal Coat and Retread
seal coat is the application of asphalt binder to a pavement surface covered with aggregate. There is no specific distinction given between surface treatment and sear coit. However, seal coat is intended for temporary surface treatment with averase life duration of about I 0 years. seal coat is also intended to:
l. Provide an abrasion and water resistant surface. 2. To improve the skid resistance of bleeding bituminous surface which had been polished under traffic. To improve light reflection and no glare characteristics of pavement surface. To provide lane shoulder or other demarcations. To alert drivers that unusual dangerous condition is near
3. 4. 5. 6.
ahead.
Sometirnes the surface is sprayed with light coating of ss-lh Emrrlsified asphalt or petroreum .rri'to rejuveiate or improve its appearance. This treatment is sometimes called, Black Seal or Color Coat.
Sheet asphalt.
It
sheet asphalt is a mixture of sand fillers and asphalt cement. is about I Yz" thick cover asphalt concrete or shL of portland
cement concrete having a characteristics of noiseless. easilv cleaned surface extensively used as surface course on urban
streets. 146
The high binder content of 9%o ta lzyo by weight makes the sheet asphalt very expensive as comp:ued wrth other serviceable types. When binder is excessively applied to what is being required, the result is unstable slickly surf,ace which is dangerous when wet.
Cold Laid Asphalt Cold laid asphalt is a mixture of coarse and fine aggregates and liquid asphalt or emulsion. The mixrure can be prepared in a central plant or field mixture. A content of 5o/o to l0% liquid asphalt
is required to permit ioating. This type of mixture
is
acceptable for low volume roadway only.
Aeration before spreading maybe required for evaporation of some solvent water, otherwise, the pavement might be over lubricated and become unstable.
Slurry Seal Slurry seal is a combination of sand, crushed stone, emulsified asphalt and water. It is an effective solution in filling cracks and rejuvenating the surface of badly deteriorated surface. The mixture contains a proportion of 1,350 kilograms fine sand, 1,350 kg. rock dust and 140 gallons SS-l or SS-lh emulsified asphalt diluted with about 80 gallons of water on hear,y or light mixer. The purpose of the operation is to fill all cracks to produce coating of about 1/8 inch thick over the entire surface area of the road. If the seal is excessively asphalted, there is a danger that the road might be slicky under traffic.
Asphalt Overlay Asphalt overlay is a layer of asphalt bound aggregate laid to an existing pavement. The purpose is to level out distorted surface or to cover cracks and ts of the pavement. If the purpose is to strengthen the existing pavement, the choice is not overlay but Asphalt Concrete tightly bonded to the old pavement with Tack Coat.
l4l
Elements of R.oads and I{ighwnYs specified to bridge deck and other structures that require lighter load. Overlay thickness could be from 50 mm to 150 mm (2"to 6").
A thin asphalt overlay is normall-1'
5-13 Aggregate for Bituminous Concrete Coarse aggregate retained on a 2.36 (No 8) sieve should be either cmshed stone, crushed slag, crushed or normal gravel.
When cnrshed gravel is used, not less than 50 mass percent of the particles retained on a 4.75 mm (No.4) sieve shall have at least one fractured face. The coarse aggregate gradation when corrrbined with other required aggregate fractions in proper proportion, the resultant mixture shall meet the gradation required under the composition of mixture for the specific tlpes specified,
Only one kind of aggregate shall be used on the project except by direction of the Supervising Engineer
Fine Aggregates Fine aegregates ing the 2.36 mm (No.8) sieve shall consist of natural sand, stone screening or slag screenings or a
combination thereof. The resultant mixture of fine aggregates when combined with other required aggregate should meet the gradation requirements under the composition of mixture for the specific type as specified.
R.oad Materials
Lightweight Aggregate Lightweight aggregate, (except slag) could be manufactured by the rotary kiln process if permiued by the special provisiotts of the specifications. The materials shall consist of angular fragments uniform in density and reasonably free from flat, elongated or other deleterious substances. It shall also show an abrasion loss of less than 45 mass percent when tested in accordance with AASHTO T96. The mass per cubic meter shall not exceed 1080 kilograms after testing through 5 cycles of the magnesium sulfate soundness test. The loss shall not exceed 10 mass percent.
Aggregates for Bituminous Plant-Mix Surfacing 'The aggregate shbuld be uniformly graded from coarse to fine. Target values for the intermediate sieve should be established within the limits given on Table 5-5.
If the crushed gravel is used, not less than 50 mass percent of the material retained on the 4.75 mm (No 4) sieve shall be particles having at least one fractured face. That portion ofthe composite material ing a 4.75 mm (No.4) sieve shall have a sand equivalent of not less than 35 as determined by AASHTO T-l'16 altemate method no.2. The aggregate shall be free of cla-v balls and adherent films of clay of other matter that rvould prevent thorough coating with the bituminous materials.
Aggregates for Hot-Plant-Mix Bituminous Pavement Open Graded Asphalt Concrete Friction Coarse Relatively, pure carbonate aggregates or any aggregates known to be polishing should not be used as coarse aggregate. In addition, the coarse aggregate fraction shall have at least 75 mass percent of particles by weiglrt, with at least two fractured faces and 90 mass percent with one or more fractured faces except that lightweight aggregates need not meet this requirements. The abrasion loss shall not exceed 40 mass percent.
148
Various aggregates fraction for the mixture should be sized, graded, and combined in such proportions that the resulting conrposite blend meets one of the gradrng requirements as prescribed on Table 5-6.
Bed Course Materials Bed Course materials for sideu'alks, paved rvatenvat's and
Elements of Roads and Highways
Road Materials
curbing shall consist of cinders, sand, slag, gravel. crushec, stone or other approved materials having 37.5 mm (l'112")
Bed materials for slope protectron should be porous and effective draining materials consisting of sand, gravel, cinders, slag, crush stone or other approved free draining materials. It should be uniformly graded wherein 100 percent of the material will through a sieve having 37.5 mm square openings.
square openings.
TABLE 5.5 RANGE OF GRADATION TARGET VALUES Sieve
AASHTO
Designation
mm
inches
25
I inch
i9
3/a
475 2.i6
BITUMINOUS PAVEMENT
(Mass percent ing square mesh sieve AASHTO T-27)
Sieve Desisnati Std. mm
50-60 38-48
8
0.075 No
TABLE 5-7 GRADATION REQUTREMtrNTS -COLD PLANT MIX
filler
100 100
No.4 No.
Square Mesh and T-27 mineral Range
T-ll
3- | The minimum sand equivalent is 35
200
Altemate US Std.
100
25
1u
85-100
20
3/4'* 1I)n
40-70
100
l0-35
95-100
4-16
l5-40
0-5
t0-2s
No.4 No.8
s
2.36 0.600 0.300
A
(t v2.)
100
(1')
95-100
2s 20
B
c
100
54-15
68-86 56-78
4.75 (No.a)
3658
36-60
2.36 (No.8)
25-45
27-47
1.18
75-95 95-100
r
riI
0-5
(Mass percent ing square mesh sieves, AASHTO T-27)
G
100
95-100
100
74.92
95-100
2747
48-70 33-53
75-90 62-82
18-37
2240
38-58
l1-28
l3-28
1
5-30
2242
9-20
I
l-28
o-e
6-20 0-8
4-8
Grading designation corresponding size No. from
AAS
18-37
0.300 (No.50)
F
mm
l l-28
(No. l6)
0.075 (No.200)
E
100
t2 (ll2') l0 (3/8")
0.600 (No.30)
D
Sievc 95-100 68-86 56-78 38-60
(314',)
4-13
TABLE 5-8 GRADATION REQUIREMENTS FOR COVER COAT
Designation
3't
No. 30 No. 50
GRADING
Sieve In.
Course
t-1t2'
4.7
rnm
Wearing (surface)
Course
38
t2
TABLE 5-6 GRADATION RANGES-TTOT PLANT MIX BITUMINOUS PAYEMNNTS (lVlass percent ing square sieves, AASHTO 11 and T-27)
Bottom (binder)
4-9
':o
95-100 45-65 30-50 33-53
l-28
l0-20
2-10
3-8
1
100
t-_tt
z-s
38
In.
l-7/2"
l"
25 20
3/4"
t2
1/2u
l0
318'
4.75
No.4 No.8
2.36 4.75
No.200
No.5
No.6
No.7
TM No.8
No.9
No.l0
100
90-100
roo 90-100
0-10
100
9G100
0-l
5
85- 100
0-15
: U2
100
100
8s-100
85-100
n-')
0-10
0-10
o-z
o--2
o-2
r-il
Elements of Roads and Highways
Road Materials
TABLE 5.9 GRADATION REQUIREMENTS FOR BITUIUINOUS SURFACE TREATMENT AASHTO T-27 Grading desigration with corresponding size number from AASHTO M-43 (ASTM D-448) modified No.5 No.6 No.7 No.8 No.9 No.l0
Sieve
Designation
mm
38 25 20 12 l0
In
l-1/2"
SALT STABILIZED BASE COURSE Sieve Designation
mm
Grading A
90-100 100 2U25 90-100 100 0-10 20-55 9G100 lm
1"
3 4" t!2',
G5 -
318'
0-15 40-70 85- 100 100 lo0 0-5 0-15 10"30 85-100 85-l0O
PRESERVATTVE TREATMENT
Grading A
Designation
Sieve 20 mm
3t4',
l0-
3/8"
2.36 0.075
4s-80 28-64
45-80 28-64
0-12
0-12
FOR SUBGRADE MODIFICATION Sieve Dcsignation Mass Percent ing square mesh sieves -
mm t-r/2" 25 mm 1' 4.75 No.4 0.075 No. 200
AASTIIO T-27
25 20 12 4.75 2.00 0.300 0.075
':o roo 30-70 0-15
70-100
50-80
5G80
4U70
35-45 25-50
3G60 2G50
5-30
lG30
No.40
I
No.200
7-15
Sieve Designation
TABLE 5.T1 GRADING REQUIREMENT$AGGREGATES
"18
100
7-1s
(Mass perccnt ing squarc mesh sieves
38
-)
100
70-100
TABLE 5.13 GRADTNG REQUIREMENTS FOR AGGREGATES FOR EMTJLSIFIED ASPHALT TREAiED BASE
100
No. 200
0.425 0.075
-
Grading B 100
No.4 No.8
4.75
mm 3" 50 mm 2" 38 1-l/2" 25 ln 20 3/4" 10 3/g' 4.75 No.4 2.00 No. l0
Grading B
75
BLE 5-10 GRADATION REQUIREMENTS FOR BITUMINOUS
75 mm
Mass percent ing square mesh sieves
Inches
100
4.75 No.4 1.7(, No.8 0.150 No 100
TA
TABLE 5-12 GRADING REQUIREMENTS FOR AGGREGATE
40-8rJ
0-20
t-1t2' ln
Grading
AASHTO llT-27
Grading
100
100
95-100
95-100
314"
50-85
100
26-59
95-100 65-100
v2, No.4 No. 10 No.50 No.200
Grading
o-s
t7-48
0-2
2-rc
12-35
3-12
Road Materials
Elements of Roads and HighwaYs
5-14 DPWH Standard Specifications on Prime Coat, Tack Coat and Seal Coat. Item 301 Bituminous Prime Coat Materials Bituminous material is either Rapid Curing (RC) or medium Curing (MC) Cutback asphalt, whichever specified. Prime coat is applied only to dry or slightly moist surface. No prime coat will be applied during foggy or rainy days.
The pump is furnished with an indicator showing the rate of liquid flow. A thermometer is fixed to indicate the temperature of the liquid immediately before it leaves the spraying bar. 7. The distribution is fumished with a Tachometer indicating its forward speed visible from the drivers seat. 8. The distributor shall be designed where the deviation from the prescribed rate of application does not exceed l0% equipped with a device for hand spraying of the bituminous liquid.
6.
Application of Bituminous Materials Equipment
1.
2. 3.
4.
5.
l_54
The liquid bituminous material sprayed by a pressure distributor with no less than 1000 liters capacity mounted on pneumatlc tires of width and load produced on the road
surface not to exceed 1000 kilograrns per centimeter width of the tire. The tank must have heating devices able to heat complete charge of bituminous liquid up to 180"C. The heating device has automatic control that overheating will not occur. The flame should not touch the casing of the tank directly containing the bituminous liquid. The liquid should be insulated that when the tank is filled with bituminous liquid at 180'C, the temperature will not drop to less than 20'C per hour when the tank is not being heated. A thermometer is fixed to the tank to measure the liquid temperature continuously. The tank is furnished with calibrated dipstick to indicate its content. The pipes for filling the tank shall be furnished an easily changeable filter. The distribution has the capacity to vary the spray width of the bituminous liquid in maximum steps of 100 mm to a total width of 4 meters. The spraying bar must have nozzles from which the liquid is sprayed in fan-shaped over the road surface equally distributed over the total spraving width.
l. The
surface to be treated shall be cleaned with broom including the removal of all dirt and other objectionable materials before applymg Prime Coat. Prior to the application of Prime Coat, the surface is slightly sprayed with water but not saturated. 3. The rate of bituminous material application is within the range of I to 2 liters per square meter. 4. Prime coat should be left undisturbed for a period of 24 hours, closed to traffic until it has penetrated and cured sufficiently, so it will not be picked-up by the wheels of ing vehicles.
The Prime Coat should not be in excess of the specified amount. Any excess is blotted with sand or removed. 6. Area not accessible by the distributor is sprayed manually using the device for hand spraying. 7. The surface ofthe road and trees adjacent to the areas being treated shall be protected to prevent their being spattered or marred by asphalt. 5.
Item- 302 Bituminous Tack Coats
of
The standard specification for Tack Coat is the same as that the Prime Coat. The difference will be enumerated as fol-
lows: 155
Elements of Roads and HighwaYs Road Materials
l.
The manner of application is either by the Rapid Curing Cutback or the Emulsified Asphalt within the range of 0.2 to 0.7 liter per square meter.
Tack coat is sprayed in advance on the surface course to permit it to dry into a 'tacky" condition. The tack coat is maintained until the next course is applied.
2.
5. 5.
The aggregate shall have a mass percent of wear not exceeding 40 when rested by AASHTO T-96. When crushed slag is used, it should be uniformed in density and qualrty. A density of not less than 960 kilograms per square meter as determined by AASHTO T-96.
Item 303- Bituminous Seal Coat
TABLE 5-15 GRAITING REQUIREMENTS
This item consists of an application of bituminous materials with or without the application of aggtegate to a bituminous
Mass
Sieve Desigration
surface course.
mm
Inch
Materials Required:
12 l0
3/8"
l.
The approximate amount of materials required for Seal
4.75 2.36
l.l8
3
Grading
A
l/2
Grading B 100
No.4 No.8
Coat per square meter is provided on Table 5-14.
No.16 0.300 No.50
Bituminous material is the Asphalt Cement penetration grade 120-150 Rapid Curing or Medium curing Cutback
0.150 No.
2.
Type- 2
100
100
100
85-1000
85-100 50-100
85-100
l0-30
lG40
0-10
0-10 0-5
1'
0-10
asphalt.
3.
Cover aggregates for Type 2 Seal Coat consists ofsand or fine screening free from dirt or other organic matter.
4.
The aggregate for Type-3 Seal Coat is crushed stone, crushed slag or crushed gravel. Only one type of aggregate shall be used in a project unless other alternative tlpe is approved.
TABLE 5-14 QUAI\TITY OF'MATERHLS FOR SEAL COAT
Material
Type-l
Type- 2
Type-
Bituminous Material L/m
.20-.50
.50-1.00
.85-l/50
None
5.00-10.00
8.00-14.00
Cover
Aggregate Kg.lrf
3
Construction Requirements
1. Seal Coating should not be undertaken 2.
on foggy or rainy
day or when the surface to be treated is wet. Wet material Cover Coat, should not be used on the work
and no Seal Coating work be continued at niglrt unless
3.
4. 5.
provided with sufficient ligtting.
Seal Coating operation should not be started until the bituminous surface is thoroughly compacted by traffic and road roller. Seal Coating should not be placed on newly constructed or reconditioned road surface in less than ten days after the surface is laid and opened to traffic. Road surface to receive bituminous material should be cleaned of dirt, sand, dust and objectionable materials. The cleaning should be effected by means of a rotary power broom or power blower.
156
t57
Road Materials
Elements of Roads and Highways
Application Of Bituminous Materials
l.
Bituminous material should be applied by means of pressure distributor at the rate of approximately 0.9 to 1.8 liters for Asphalt Cement and 1.5 to 3.0 liters for Cutback Asphalt per square meter of surface in a uniform, unbroken spread over the section to be treated.
2. The pressure distributor
specifications including its appurtenances are the same as that enumerated in item 301 Bituminous Prime Coats. Those that differ will be disapproved.
3. 4.
5.
bituminous material at the junction of spreads should not exceed the specified quarrtity. Any excess should be removed from the surface by squeegee. [fnecessary to obtain properjunction ofspreads, a trip of Manila paper approximately one meter wide and at least as long as the spray bar should be used at the beginning and end of each spread. The paper is removed immediately after use. Any skipped areas or recognized deficiency should be corrected immediately by hand application of operated
Application
of
pressure device.
Spreading of Cover Aggregates
L
lmmediately after the application of asphalt, the cover aggregate should be spread evenly over the surface at the rate of approximately 0.004 to 0.007 cubic meters per
even distribution then rolled with an approved power roller weighing not less than 5 nor more than 6 tons to a uniform surface.
Item 304 - Bituminous Treatment This item consist of either single application of bituminous material followed by a single spreading of aggregate (single surface treatment) or two applications of bituminous material each followed by spreading of aggregate (double surface treatmenl) TABLE 5-16 QUANTITY OF MATERIALSAND SEQUENCE OF OPRATIONS USING CUT-BACK OR CEMENT ASPHALT Aggregate Grading and Sequence
Double
Operation
S.T.
FIRST COURSE: Applying Bituminous Materials, liter/ sq. m. Sprcad Aggrcgate: Grading B, kg. / sq. meter Grading A, kg. / sq. mcter SECONDCOT'RSE Applying Bituminous Matcrials, liter / sq. mctcr Spread Aggregato Grading B,kg. / sq. motor Bituminous Material, litcr / sq. meter Aggrcgatc, kg. / sq. mctcr
1.58 10.88 1.36 13.@
2.94 38.0
square meter. 2.
4.
158
Spreading of the Aggregate Cover is done through aggregate spreader, to obtain an even and accurate distribution. The used of spreader board attached to the tailgate of the tmck, should not be permiued. Tires of the aggregate truck should not be allowed to come in with the uncovered and newly applied asphalt. After spreading the cover aggregate, .the surface is broom lightly with an approved push or drag broom to insure an
Materials Requirements
l.
The approximate amount of materials per square meter and sequence of operation for single and double surface treatment is provided in table 5-16.
2.
The quantities given in the table are those aggregates having a bulk specific gravity of 2.65 as determined by AASHTO T-84 and T-85. 159
Road Materials
Elements of Roads and HighwaYs
3.
The supervising engineer may adjust the amount of asphalt material per square meter if necessary, to fit into the prevailing condition. But the total amount of aggregate per square meter after adjusting for specific gravity will not be changed.
Mass Percent Fassins Sieve Designation
Bituminous material for surface treatment is either slag or crushed gravel. Only one type of aggregate should be used in the project unless alternate type is approved. The aggregate shall have a mass percent of wear not exceeding 40 when tested under AASHTO T-96. When crushed gravel is used, not less than 50 mass percent of the particles retained on the 4.75 mm (No 4) sieve shall have at least one fractured face. When crushed slag is used, it must be of uniform qualrty and density of not less than 960 kg. Per
(AASF[[O T-19)
TABLE s-1? QUANTITY OF MATERIALSAND SEQUENCE OF OPERATIONS USING EMLTLSIFIED ASPIIALT
25 20 t2 l0 4.75 2.36 1.18 0.30
l.
Bituminous Matcrial, litcr / sq. mcter Aggrcgate kg.i sq. mcter
Grading
Grading
A
B
C
100
314"
90-100
t/2"
20-55 0-15
85-100
lm
0-5
10-30
85-100
0-10
lG40
0-5
0-10 0-5
318'
No.4 No.8 No. 16 No. 50
t00
The contractor or supplier shall furnish the engineer cerf-ified certificate in duplicate of the asphalt materials delivered to the site.
2.
S.T.
3. 1.58 13.@
SECONDCOURSE: Apply Bituminous Matcrial, liter / sq. m. Spread Aggregatc, Grading C, kg. / sq' m.
ln
Grading
Construction Requirements
Double Aggregate Grading and Sequence Operations FIRST COI.JRSE; Apply Bituminous Matcrial, liter / sq. meter Sprcad Aggrcgate: Grading B, kg' / sq. m€ter
Inch
mtrn
Bituminous Materials
square meter
TABLE 5-18 AGGREGATE GRADINC REQUIREMENTS
The contractor shall provide rveighing equipment on the site to control the application of aggregate. It ntust have an approved multiple beam twe scale with indicator and other necessary dials protected by a weatherproof house with floor area not less than l0 sq. meters. A mechanical spreader is used for spreading ther aggregate, capable of spreading the aggregate uniformll' over the full width of the area being treated, and shall irave a control to regulate the feed gates, the feed roll, the auger and truck hatch.
Application of Bituminous Material 1.58 13.60
1.
The application of bituminous material is done onll' rvhen
the weather condition is dry and favorable. Spraving should not be done unless the road temperature is above 20"C for at least one hour prior to the conrmencemcnt of
Elements of Roads and Highways spraying operation and the temperature is not less than
Road Materials trtem 305
20oC during the spraying.
-
Bituminous Penetration Macadam Pavement
Asphalt material is applied to the surface at least 24 hours after it has been Prime-coated.
The asphalt material should be applied on dry surface whenever cutback or asphalt cement is used. The surface
should be lightly wetted with water when emulsion asphalt is to be used.
lhe
This item consists of furnishing and placing one or more courses ofgraded aggregate and one or more application ofbituminous materials, followed by Seal Coat cover aggregate constructed on a prepared base. rABLE s-re
recommended application temperature for asphalt cement is within the range that produces a viscosity of l0 to 60 seconds savbolt fural. And for cutback Asphalt with
the range given in item Bituminous Material, the ideal tcmperature is rvhen fogging occurs.
Spreading the aggregates
Type ofAggregate and Sequence of Operations
of Bituminous Materials Asphalt Cement or Rapid Curing (RC) Asphalt
FIRST LAYER:
lmmedratell' after applying asphalt material, the dry ag-
gregate is uniformly and evenly distributed over the treated surface by an approved mechanical aggregate spreader.
2. Truck delivering aggregate
AND SEQUENCE
OF OPERATIONS
Spread
l.
QuANrrr"""sffirxffiLs
Aggregale 314"
Coarse Aggregate, kg.
/
sq. m.
on
Choker Aggregate, kg.i sq. m.
l0
Apply Bituminous Material, li1rlrl m2
5.5
SECONDLAYER:
shall move backward in
spreading aggregate to prevent the tires and the mechanical spreader from rolling directly over the newly sprayed asphalt.
3.
No portion of the sprayed surface shall remain uncovered for a period of more than 2 minutes. Immediately after spreading the aggregate, treated surface is rolled with an approved pneumatic tire roller.
4.
Asphalt materials that are exposed during rolling operation. should be covered r,vith additional aggregate and furtlier rolled until an even surface is attained.
5.
Traffrc should be prohibited from ing at speed in excess of 40 km. per hour before the asphalt material com-
Spread Aggregate Key Aggregate, kg./ sq. m. (112") Apply Bituminous material, literl mz
l0 3.5
THIRDLAYER: Spread Aggregatc Key Aggregate, kg./sq. m. Apply Bituminous material, literl m2
FOI.]RTHLAYER: Spread Aggregate CoverAggregate, kg./ sq. m.
TOTAL QUANTITIES: Bituminous material, liter / sq. m. Aggregate, kg. / sq. meter
pletelv set. 162 163
Road Materials Elements of Roads and Highways
3. Material Requirements The amount of materials per square meter and sequence operations shall be as provided in table 5 - I 9.
of
Bituminous Material is either Asphalt Cement Rapid Curing Cutback Asphalt or Emulsion Asphalt whichever is specified.
Aggregate should be crushed stone. crushed slag or cntshed gravel consisting of clean, tough, durable fragments, free from excess of flat, soft or clisintegrated pieces and free from stone coated u'ith dirt or other objectionable nutter. Natural gravel may be used for cover material. Aggregate shall have a mass percent of wear not exceeding 40 rvhen resred b-v AASHTO T-096. *When crushed gravel is subjected to five cycles of the Sodium Sulfate Soundness Test (AASHTO T-104), the weighted loss shall not exceed 12 mass percent. *When crushed slag is used, it shall be uniform density and qualrty. A density not less than 1,120 kilograms per sq. m. as determined by AASHTO T-19. Application of bituminous material should be made only when the aggregate is dry and the atmospheric temperature under the shade is l5"C or above and the weather is not foggy or rainy.
The roller should be self-propelled steel wheel, vibratory or pneumatic type. Its weight should be suffrcient enough to compact the layer of the required conditions.
TABLE 5-20 AGGREGATE GRADING REQUIREMENTS
mm
Grade
4.75
236
1.18
No.4 No.8 No.16
A
GradeB
!
GradeC
Grade D
100
9G100
35-70
Gl5 100
0-5
90-100 40-14 0-1 5
90-100 20-55
100
0-1 5
85- 100
0-l
)-u
5
10-30
0-10 o-5
Base Preparation
l.
Before spreading the aggregate, the base is properly cleaned of all loose foieign materials. The existing base is swept until the embedded large aggregate is erposed or in the case of previously constructed asphalt until the surface is free from mud or other covering.
The equivalent to be used shall include, a) I:land or power operated brooms, b) Shovel
c) Rakes. d) Self powered
bituminous material distributor hand or power operated spray pumps, broomdragging equipment and self powered rollers.
2. A
Inch
62 2-l/2" 50 2n 38 l-ltz' 25 ln 20 314* 12 712* l0 3/8'
Equipment
1.
Mass Percent
Sieve Designation
sufficient number
of
stiff-fiber steel bristle
push
2.
Prime Coat is applied to the prepared untreated base, or in case of previously constructed asphalt, or cement surface, Tack Coat is applied.
3.
During the application of asphalt materials, building paper is laid over the end of the previous application where the new application will start on the building paper.
4.
The distributor should not be cleaned or discharged into ditches, borrow pits or shoulder along the right of way.
brooms is included. 165 I
i
lii
164
Road Materials
Elements of Roads and Highways
Item - 306 Bituminous Surface Course Bituminous material is either Rapid Curing (RC) cutback, Medium Curing (MC) Cut Back or Emulsified Asphalt whichever specified. The proportion of bituminous material on the basis of total dry aggregate is from 4.5 to 7.0 mass percent when cut back asphalt is used and from 6.0 to 10.0 mass percent when emulsified asphalt is used. During the mixing operation, one half to one 0.5 to L0 mass percent of hydrated lime, dry aggregate basis is added to the mixture. The lower percentage limit is applicable to aggregate which predominantly calcareous.
l. 2.
3.
The equipment includes bituminous distributor and heating equiprnent, scarifier, mixer, spreader, and finishing compactlng cquipment. Road rollcr should be Self Propelled Steel Wheel tandem of 3 rvheel rollers weighing not less than 8 tons each and a Pnc:urnatic Tire Rollers having a total compacting width of not les than 1.52 mm (60 inches) and the gross mass
adjustable within the range of 3,540 to 6,360 kg./m. of compaction width. All tires of Pneumatic Roller is equally inflated exerting equal unit pressure with mass of varying pressure to suit project condition.
Base Preparation
Case I(NewAggregate) When new aggregate is used for the road mix surface course, the existing base is scarified lightly and bladed to a uniform grade and cross section as specified Case
1.
t66
- II
( Salvaged Aggregate)
When materials in the existing road surface are to be used for mixing, the surface is scarified lightly and bladed to a uniform grade and cross section. Tlie re-shaped surface is
scarified to depth as defermined by the Engineer to leave a foundation of undisturbed material parallel in profile
2.
and cross section to the finished surface.
The loosened materials are bladed aside into windrow side of the road, and {he undisturbed materials rolled, watered, and rolled as dirested.
5-15 Geoplastic Fabrics The Geoplastic fabrics were introduced and experimented in Europe in the year 1970. Thpy were used to reinforce soil of pavement and to provide drainage and erosion control for highways and railroads.
According to FF{WA report RD 80-021 enititled Evoluation Test Methods and Use Criteria for Geotechnical Fabrics in Highway application", the use of geoplastic fabric is considered as excellent. The evaluation was ed by Koemer and Welosh in "Construction and Geotechnical Engineering Use of Synthetic Fabric" published in New York year 1980.
The Functions of Geoplastic Fabrics
L 2. 3. 4. 5.
As Filter.It holds the soil in place while allowing water to flow easily away by some form drainage. As Drainage. Heavy geoplastic fabrics -provide channels for carrying water away from the soil to the drain. As Separator. The fabrics prevent different materials from mixing together. As Reinforcement.It adds mechanical strength to the soil of pavement structure. As Armor.It protects the soil from surface erosion or attractive forces.
Materials
Euplastic fabrics are manufactured from polypropylene, polyester, nylon, polyethylene and polyvinylidene chloride
of t6'1
Elements of Roads and Highways
CHAPTER
which changes in properties depends on the processes by which the fabric is produced aside from the differences in chemical composition. Most of these Geoplastic materials are made of polypropylene and polyester.
DRAINAGE AND SLOPE PROTECTION
Differences in Properties Includes:
1. Specific Gravity
5. Creep resistance
2. Strength 6. 3. Future stain 4. Modulus of elasticity.
Resistance to ultra-violet light and biological effect.
6-1 Drainage
Construction Methods are classified as either Woven or Knified non-woven. -l.or Woven Fabrics, the filaments are directed in two perpendicular directions and overlapped. For transportation use, the pattern is simple uniform and rectangular constant pore size distribution. The Monofilament Fabrics are woven from single strands and the Multifilament Fabrics are made h'om yarns with many fine strands. The Ribbon Filament Fabrics are made from strands with widths several times their thickness.
KGF) is made of loops of fibers by straight segments. They could be stretched in ei-
Knitted Geoplastic Fabrics corurected
ther direction without significant stresses to the fabrics. Knitted Geoplastic Fabrics in tubes serve well as filters around drain tile particularly for agricultural needs. Non-Woven Geoplastics are neither woven or knitted. The fibers or strand arrangements are held together under the following marmer:
l. 2. 3.
Needle punching through the fabrics.
4.
Combination bonding is the combination of two or more ofthe processes described to produce a particular charac-
Heat bonding or melt bonding
Resin bonding wherein the fabric is impregnated resin wh^ich cements the fibers together.
teristics.
I68
with
a
Drainage is defined as the me:lns of collecting, transporting and disposing of surface water originating in or near the right of way, or flowing in stream crossings or bordering the right of way.
ApproximatelS abofi 25Yo of roadway firnds are spent for culverts, bridges and other drainage stmchrres. Bigger appropriations are also allotted for ditches, dikes, charmels and erosion control structures of rural roads. Likewise, major capital investnents are channeled to urban areas for storm drains and other appurtenanoes plus the routine clearing of drainage facilities.
Surface drainage is only one :unong the many problems to be considered in establishing the location and construction of roads. The most favorable location of a roadway as far as drainage is concerneS, is the division bstween large drainage areas. All streams must flow away from the right of way to reduce the drainage problem. Roadway location parallel with the large streams should be avoided because it will cross every tnbutary canal leading to the streams. Steep grades, and heavy cuts and fill, should likewise be avoided for it will contribute to the problems of erosion. Surface drainage problems
l.
follow three basic considerations:
Hydreulic design that deals with estimating the highest rate of run-offto be handled.
Drainage and Slope Protection
Elements of Roads and Highw*ys
2. 3.
Hydraulic Design deals with the seiection of the kinds
drainage pattern. Water ing the natural right of ways several streams are collected, to under the highway through
is often intercepted by road cuts. The flow of
and sizes of the drainage facilities that is most economical to accommodate the estimated water flow. Erosion Control is to ascertain the design will not create erosion or other unacceptable en"ironmental conditions.
a single channel, diverting streams to canal or culverts that differ in sizes and length urcluding the flow characteristics from the previous one.
6-2 Hydrology Hydrology is that branch of physical geography that deals with water of the earth. The branch of hydrology that concern highway engineers are:
l.
2. 3. 4.
The frequency and intensity of precipitation. The frequencies that this precipitation brings the highest run-offwhich are equal or exceeded critical values.
The distribution of precipitation throughout the seasons that influences water behavior affecting the highway surThe prediction regarding future rainfalls or run-off from gathered statistical approaches, formula, or simulated msthods based on the laws of probability.
probability of error.
Runoff is Predicted Based on the Following Methods: Bythe Rational Methods. By the Empirical Formula. By the Unit Hydrograph. By Statistical Approach. By Simulation.
Relationship and Effect of Hydraulic and Construction
l. 170
Usually, highway construction disrupt existing natural
Construction operations may disturb the ground cover, and loosen the soil creating muddy stream as a result of erosion.
3.
Erosions create debris that are carried downstream, and deposited at points where the velocity slackens. Record shows that, almost every drainage installations disturbed the ecoiogical balance of nature.
4.
Any changes in the land use may alter the historical runoff or un-gauged rural water shed that could be disastrous on wide scale basis.
faces.
Concomitant thereof, any methods of predicting may be subject to substantial error. Therefore, design should make the best possible use of existing methods, with full expectations of high
l. 2. 3. 4. 5.
2.
Cardinal Rules on Drainage Design
l.
As much as possible, any exisfing drainage terns and soil cover should not be disturbed.
2.
system
Wt-
Necessary changes in the drainage patterns should not in any manner bring velocities that may create new erosion
problems. Non-observance of these simple rules have created many serious problems in the past, and worse, the people put their blame on those who were not involve in making the highways very unsightly.
6-3 Drainage Economic Considerations The term economy in drainage system, simply mean; finding the solution to a problem that is cheapest in the long run under the followins conditions: 171
Elements of Roads and Highways
l. 2. 3.
Determine the estimated initial investment cost. Consider the maintenance cost or outlay. Consider anticipated.loss and damage for each solution.
Under the foregoing considerations, arurual appropriation for possible drainage or economic loss is equal to the estimated losses from floods of various magnitudes, multiplied by the probability that these floods will occur any tirne of the year. For instance, if the drainage loss from any flood exceeding the design flow is P200,000 and according to hydraulic computations such floods will occur once in every 5 ysars, then the annual loss of flood damage is F200,000 divided by 5 years or
Drainage and Slope Protection road pavement under tlre influenc€ of the cross section slope or super elwation in the pavement and shoulders. If the water flow is controlled, then, the shoulder is in danger of erosion. However, t'he shoulder will have minimal erosion damage if it is already covered or protected by turfor grass.
1.
2.
Water flowng across tlre roadway down the road slope must be thin enough in a sheet form like so that the erosion on tlre shoulder will be minimized. Unprotected slope could be badly washed out if irregularity in the pavernerfi or shoulder accumulates water into small streams. Another point of water accumulation that endangers the shoulder is the low portion of sagged verti-
3.
cal curves. One way of preve,nting washout of the side slope is to retain the water at the outer edge of the shoulder.
P40,000 per year. Drarnage problem is varied" and there is no single sst of assumption or rule to economic problem in drainage, considering the uncertainty of flood frequency where the design is based. To major highways with large volume of traffic, losses to motorists
and to the economy, is tremendously high, closed frequently, due to flood and washout.
if
Turf slope not less than 0.12 Pavement slope approx. 0.04
the road will be
For major highways, projections might proved that drainage facilities should accommodate a 50 year flood, whereas, the desrgn based on a 5 year flood is reasonable for a low volume rural roads.
Low fill slope 4:1 or 6:1 approx. 1.5 m. High till slope 2:1
Where drainage problem of any magnitude has allernative solution, economic studies based on reasonable estimated costs and possible dam4ges, represent the best approach. Flood frequencies and some of the costs, must be thoroughly approximated and let catastrophic occurrences pervert our perspective
Shoulder Turf sloDe not less than 0.12 Paved slope approx. 0.04
on cost risks.
4:1 slooe or flatter
G4 Draining the Highway Rain water flows laterally or obliquely on the surface of the
FIGURE
A1
TYPICAL HIGHWAY CROSS SECTIONS
Drainage and SloPe Protection
Elements of Roads and Highways 4.
5.
A crown ditch or intercepting
channel mav be employed at the top of the cut slope. This will prevent erosion of the cut slope by surface runoff from the hillside above. The surface should not be disturbed in any manner where the natural ground is already covered with grass or other ground cover. The channel or canal should be formed making the origi-
nal ground as its bed and a small dike of topsoil or imported materials to serve as its bank. Scouring must be controlled. If possible, the water flow must be limited to a safer amount by diverting the flow at intervals. Water should be dropped down to the roadside ditch b]'means of specially designed conduit or channels.
c = Runoffcoefficient expressing rate of
I = lntensity of rainfatl in inches per hour for a duration equal to the time of concentration'
Ad = Drainage arca in hectares. On Freeways and urban strests, ttre inlets for gutters and median should the designed flood without clogging with debris. TABLE 6-1 SUGGESTED VALUE OF COETFICIENT OF RUNOFF C, FOR USE IN THE RATIONAL FORMULA
2. 3. 4.
On city streets, rain waters is guided by the road slope to the gutters and along wrth them the curb and inlets designed to limit the spread of water over the traffic lanes. AASFITO recommended that for a grade materials water should not encroach on the outer lane by more than 1.80 meters for a l0 years flood. A 50 years return penod is proposed for depressed facilities. The decision for water storm inlets and connections for gutters and depressed median should be based on the same periods. Main storm drain for freeways has to accommodate 50 to 100 years storm. For arterials, the return interval is 20 to 50 years. The water flow estimate was based on the Rational Formula using the value of runoff coefhcient between 0 8 and 0.9 for pavements; 0.4 and 0.6 for gravel, and 0.1 and 0.7 for grass.
RationalFormula: Q
=
clAd
Where:
Q: t74
Quantlty of runoff in cubic foot per second
Coefficiency of Runoff
Type of Drainage Area
Draining the Urban Street
l.
the ratio or
runoffto the rate of rainfall
Concrcte or Bituminous Pavcment Gravel Roadways, open Bare Earth ( high value for ste slope)
0.8 - 0.9
Turf meadows Cultivated fields
0.1 - 0.4
Forcsted areas
0.1 - 0.2
0.4 - 0.6 0.2 - 0.8 0.2 - 0.4
6-5 Manhole, Inlets and Catch Basin Manhole, inlets and catch basins are classified under Itent 502 of the DPWtl,,standard specifications which includes construction, reconstruction or adjustrnent of manholes inlsts and catch basin
Material Requirements:
l. 2.
Units' Whsn bituminous
coating is specifiled, it shall conform to ASTM D-1187, Asphalt Ease Emulsion as protective coating for metal' Sewer and manhole made of bricks from clay or shale must conform to AASIITO M-91 standard specifications' Building bricks of solid masonry units made from clay or shale must conformto AASIITO M-l14' Comrgated Metal
t75
Drainage and Slope Protection
Elements of Roads and Highways
3.
4.
t mortar mixture should be one part Portland cement and two parts fine aggregate (gravel) plus hydrated lime equal to 10% of the cemelrt by weight. Frames, gratings, covers and ladder rungs, should be assernbled before shipment and may be re-assembled readily'in the same position when installed. lnaccuracy of bearings must be corrected by machine. The frame, gating or cover to be used must constitute one pair.
Al1 casting should be uniformly coated wittr asphalt base emulsion meeting the requirements sf ASTM D-l18?.
Stuctural concrete for the purpose must attain a minimum 28 days compreSsive stength to 20.68 Mpa (3000 psi). precast unit must be cured and the water absorption of individual cores must not exceed 7 percent.
If
certified for use at 14 days from the date of casting. If the strength is not met at 28 days, atl units made from that batch will be rejected. Cracks in units, honeycombed or patched areas in excess of 2,000 squ:lre millimeters, excessive water absorption and failure to meet strength requirements will be rejected.
Construction Requirements Concrete conskuction must conform to the requiremeirts
for ltsm 4O5-Stuctureal Concrete. Metal frames should be set in full moitar bed and pipe sections flushed on the inside of the structure wall projected outside sufficiently !
i
2. 3.
for proper connection with the next pipe section. Masonry shall fit neatly and tightly around the pipe. When grade adjusftnent or existing structure is specified, the frames, covers and gratings are removed and then reset to the specified elevation.
Upon completion, each structure should be cleaned of anv accumulation of silts, debris, or foreign matters r:f, any kind until final acceptance of the work.
Methods of Measurement Standard manhole inlsts and catch basins be it new, or reconstructed will be measured in unit. Any authorized additional
concrete, reinforcing bars, masonry or labor required, will be measured and paid for under Item 404 and 405. Junction Box structure is measured for paynent as a manhole. The number of concrete covers, pairs of metal frames and gratings, pairs of metal frames and covers, will be rneasurecl as acceptably completed. Likewise, the number of existing manholes, inlets and catch basins will be nreasured as acctabll' completed.
Sufficient number of cylinders shall be cast from the concrete for each unit that will permit compression tests for 7. 14, and 28 days. And to allow at least 3 cylinders for each tests. tlrc strength requirement is met at 7 or 14 day, the units will be
l.
4.
6-6 Channel The purpose in deg a charxrel is to determine the cross section of the canal that will accommodate water flow smoothl,v and cheapest to construct and maintain.
1.
Side slope with a ratio of 2:l or even flatter is most acceptable, except on rock or other hard materials wfierr: channels are lined. For unlined or unfinished channel surface, the best cross section requires the least total excavations.
2.
The design of crown ditches, gutters, stream channels, and culverts flowing partially or fully, are based on the principles of flow in an open canal. For uniform flow, the relationship is expressed in the Manning Formula:
Q= vA = (ARz S1'z) nx3
where:
Q=
Quantitv of discharge in meter per second
Drainage and SloPe Protection
Elements of Roads and Highways
R_
Hydraulic radius in meter. This is the area of the
[=
flow across section divided by the wetted perimeter. Area of the flow cross section in square meter
s=
Slope ofthe channel.
|rf = Manning roughness coefficient
(see
table 6-2)
Unless the possibility of erosion is eliminated within a reasonable lirnit, channel design is considered not a completq unit.
1.
2. 3.
T,ABLE 6.2 REPRESENTATTVE VALIINS OF ROUGHNESS
Types of Lining Ordinary eartl5 smooth gravel
Rough rubble or jagged rock Rough concrete Bituminous lining Smooth rubble
Well maintarned grass-depth of flow over 15 on. Well maintained grass-depth of flow under 15 cm. Heavy grass
Value of n 0.02 0.04 0.02 0.02 0.02
0.04 0.06 0,10
The condition to various channel problems rest on the following distinctions:
a)
b)
Water flowrng down a mild slope in an open canal is in Sub-critical flow. Water flowing on steep slope is in Super critical flow.
Sub-critical flow exists when the depth of water in the channel is greater than the critical depth.
Super-critical flow exists when the depth is less than the critical level. The Critical depth occurs when the velocity head is one half the average depth.
The Average depth or Mean depth is the cross sectional area of the flow divided by its width at the liquid surface.
4. 5.
The actual velocity must be checked against the maximum values for unprotected earth. Where channel scouring is indicated, reduction of water velocity should be adopted to a safe level. To'reduce the velocity is to reduce the flow of water by diversion.
Where diversion is not possible, the channel is widened, or lengthened. As an alternative, the slope of the channel is decreased. Baffles, checks or drops are introduced to reduce slope in the channel.
TABLE 6.3 MAXIMT]M SAFE VELOCITY WHNN CIIANNEL EROSION IS TO BE PREVtrNTED
Tlpes of Lining
Allowable Velocity in ft. per second
Well establidhed grass on any good soil
6
Meadow type of blue or bermuda grass Bunch grasses, exposed between plants Grains, stiff stemmed grasses that do
2-4
Bend over under slnllow flow
Earth without vegetation Fine sand or silt, little or no claY Ordlnary firm loam Stiff clay, highly colloidal Coarse gravel Clay and gravel Soft shale
) 2-3
t-2 2-3 4 4 4 5
6-7 Culvert With the exception of storm drain, culvert
urcludes all closed conduits with standard designs repeatedly used'
Drainage and Slope Protection
Elements of Roads and Highways
l.
Culvert is loaded vertically by the wheel load of vehicles; the earth fill covering the culvert; and the horizontal ive or active earth pressure. The magnitude of these loads are uncertain as they are influenced by:
a. b. c. d. e.
2.
Depth of the cover.
Nature and density of the overlapprng and adjacent soils. Trench width and depth. Deformation of the pipe under load. Field construction procedures.
Comrgated metal pipes are more flexible that could tolerate greater deformations. The sides of the comrgated metal pipe deform laterally against the adjacent backfill under vertical load and the horizontal earth pressure increases the load carrying ability of the pipe. 4.
5.
Materials
The stress calculation for pipe culverts are based on the assumptions regarding the methods of under pipe soil at its sides and loading distribution over it.
Highway engineers rarely make struchrral design for pipes and culvert because of the difficulties and uncertainties involved. Instead, they used past experience and records as guide, then develop standard plans to fit all normal situations.
Corrrugated metal Plain or reinforced concrete Asbestos cement Vetrified clav or cast iron
FIGURE 6-2 CULVERT PIPE
mm]l Single
Double or multiple span
For concrete, vitrified clay and cast iron pipe, what is specified is the strength or class of pipe to be used in each condition. For comrgated metal pipe, highway engineers prescibe plate thickness for the different pipe size and the heights of fill.
nn
lt
is now the practice of relying much on the recommendations of various manufacturers who prepared all the de-
:
Single
) r
I
I I I
,J
Double or muftiple span
sign data and computations etc. 7.
180
Highway agency has standard drawing of various culvert desrgn appropriate for the more cornmon heights and widths of openings, heights of fill, including skew angles
FIGURE
G3
BOX CULVERT- REINFORCED CONCRETE
18t
Drainage and Slope Protection
Elements of Roads and Highways
Installation of Culverts In order to safeguard the culvert and to prevent subsequent settlement in the roadway surface, standard procedures for culvert installations are given special attention particularly the bedding (footing) and backfilling.
l.
.t
Culverts are installed
in the original bed of
10. The L qpe headwall create serious accident hazard, thus, gutter inlet with grate cover is recommended. I l. A wing type wall is recommended for large culverts. The flared U and warped walls are used on special applications.
Under Item 500 of the DPWH standard specifications, the construction or reconstruction ofpipe culverts and storm drains strearn with
are classified as Conduits.
their slope and flow line conforming to the natural channel or canal. The stream flow should not be disturbed to minimize the tendency of erosicn. ln mountainous or rolling terrain, departure from charurel aliggrment, either upstream or downstream, may divert the current flow to one side ofthe channel. This is dangerous to create erosion and deposition on the opposite side. Culverts on skewed channel are relatively longer and costly. But channel changes and erosion protections are provided with struclnres at one or both ends to reduce the
U . TYPE
skews. 4. 5.
Inverted siphons should be avoided rvhenever the water carrics sediments of debris. Stagnant water trapped inside the culverts sag is highly objectionable that must be avoided.
6.
n L
8.
I
l
Most culverts start upstream with headwalls and terminate doq'nstream with end wall. The headwalls direct the flow into the culvert proper, while the end walls provide transition from the culvert back to the regular channel.
WING TYPE
FLARED TYPE
Hydraulically, the headwalls and end walls functions separately but both retain the embankment and protect it from washout. In most cases, cut-off wall is extended to the level of expected scour. Sometimes a paved apron or energy dissipater is extended beyond the cut offwall. The use of small pipe as end wall and sometimes headwall is being discouraged because they are hydraulically inefficient as entrances. Instead, the pipe is extended beyond the toe of the embankrnent.
WARPED TYPE
STEPPED U . TYPE
FIGURE 6-4 TYPICAL HEADWALLS AND ENDWALLS FOR CULVERTS
Drainage and SloPe Protection
Slements of Roads and Highways
Conduits
-
2. The lower segment
of the conduit pipe should be in
with the shape throughout its full length.
Conduits are laid on bedding or footing that conform with the following standard specifications:
l. Z. 3. .1.
5. 6. 7. L 9.
Conduit Bedding is classified into Class A, B and C. In laying culvert pipes, the reqrdrernent of class C bedding is applied if no bedding class is specified.
Class
A
bedding shall consist
of a continuous
concrete
cradle conforming with the plan details. Class B bedding is extended to a depth not less than 30% of'the vertical butside diameter of the conduit pipe. The minimum thickness of the bedding materials bsneath the pipe is 10 centimsters composed of sand ing a 9.5 mm sreve but not more than l07o es 0.075 mm sieve. "trhe layer of bedding material is arranged and shaped to fit nr the conduit for at least 15% of its total height. When a bell and spigot type is used, the recesses in the bottom trench are shaped to accommodate the bell.
Ckiss C
bedding should be extendeel
to a depth not
Class A
Note:
Bc + 20 min.
1. For class B and C beddings, subgrades should be excavated or over excavated, if necessary, a uniform foundation free of protruding rocks may be provided 2. For class A or other unyielding foun' dation pipe should be free frrim shocks if blasting is anticipated in the area.
Class B Bc + 20 mrn pBc p max = 0.5
than llYa of its total height.
Pipe Cornrgation on Depth
Compacted
granular
1/6 Bc min
less
compacted
For flexrble pipes, ttre bed is roughly shaped and a bedding bl;r:rket of sand is specified as follows:
114 Bc
1/4 D min.
d
granular Granular foundation
material
Granular Foundation
Minirnum Bedding Depth
l0 mm
25mm
25 mm 50 mm
50 mm 75 mm
material or densely compacted backfill
Depth of bedding Material below pipe
Class D
D
smaller m. larger
.65 m and .75 to 1.50 1.65 m. and
dmin 75 mm 10O mm 150 mm
For a large diameter structural plate pipes, the shaped bed need not exceed the width of the bottorn plate.
Flat subgrade
Bc H
Laying tlre Conduit Pipe
D d
L lnstallation of conduit pipes should start at the down-
= outside diameter = bacKill cover above top of pipe = inside diameter = depth of bedding material below
stream end of the conduit line. 2.
The lower segmelrt of th€ conduit pipe should be in contrast with the shape throughout its full length. FIGURE
18,1
6.5 BEDDING CLASS AND LOAD FACTORS 185
Elements of Roads and Highways clAss A ReinforcedA3 = 1.0% Reinforced A3
Plain
=
0.4016
Drainage and Slope Protection 3.
Lt = 4.8 L1 = 3.4 Ll = 2.8
Bc + 20 min
4.
Bc + 20 min. Densely compacted backftll
y
lt9H
I
15 min
r.lo 10 min
Plain or reinforced
Compacted
concrete 2000 psi
granular
5.
The bell or groove ends of rigid conduits and outside circumferential laps of flexible conduits are placed with longitudinal laps or seams at the side. Paved or partially lined conduit pipes are laid with the longitudinal centerline of the paved segment coincides with the flow line of water. Elliptical and ellrytrcally reinforced conduits are placed with tlre major axis within 5 degrees of a vertical plan through the longitudinal axis of the conduit.
material Concrete Arch
ing the Conduit Pipes
Class C
backfill Compacted granular material Granular Foundation
1.
Compacled granular
a) Portland cement mortar or grout. b) Rubber gaskets. c) Oakum and mortar or t compound. d) Plastic sealing compound. e) A combination of these qpes or any other :rs rnay
Granular Foundation
15 min
D
Depth of Bedding Material below oiDe
65 m. and
dmin
smaller
75 mm
to 1.5O m 100 mm Lq5 m. and larger 15O mm
be specified.
.75
backfill
2.
Flat subgade
I
1. For class and C beddings subgrades should be excavated or over excavated, if necessary a uniform foundation free of pro-
truding rocks maybe provided 2. For class A or other unyielding foundation, pipe should be free
from shocks if blasting is anticipated in the area.
FIGURE
186
In ing conduit pipes, the ends are frrlly entered into the inner surface evenly flushed. ts are connected by:
material
€H Loose
Rigid conduit pipes are the bell and spigot type, tongue and groove, or other types that may be specified.
Lr = 1.5
Lightly compacted backfill
Oensely compactecl
Legend Bc = outside diameter H = backfill coyer obove top of pipe D = insidediameter d = depth of bedding material A3 = area of transverse steel in the cradle or arch expressed in 016 of area of concrete at invert or crown
J.
4. Source: American Corrcrete Pipe Ass.
6-6 BEDDING CLASS AND LOAD FACTOR
5.
t mortar for concrete pipes consists of I part by volume of Portland cement and 2 parts of approved sand with water necessary to obtain a refined consistency. Mortar should be used immediately within 30 minutes after its preparation. Mortar t is made with excess mortar to form a continuous bead around the outside t of the pipe and smoothly finished on the side. Rubber gaskets are installed to form a flexible waterhght seal. When Portland cement mixture is used, the completed ts are protected against rapid drying by any suitable covering materials. Flexible conduits are firmly ed by coupling bands. 187
Elements of Roads and l{ighwnys
Backfilling Backfilling follows after the laymg installation of conduit pipes under the following specifications:
l. Materials for backfill should be fine, readily compacted soil or granular material selected fiom approved sources. It should be placed on each side of the conduit for the firll trench width up to elevation of 30 cm. above the top of the pipe
Backfill rnaterials should be free from stones ttrat wculd be rstained on 50 mm sieve, nor chunks of highly plastic clay and other objectionable matenals. 3.
At least 95% of the grarrular backfill materials es the 12.5 rntn sieve and not less than 95% of it are retained on a4.75 mm sieve.
4.
Oversized materjals if present should be removed.
5
On top of the trench, backfill materials are placed at or near optimum moisture content and compacted in layers not exceeding 15 cm. (compacted) on both sides up to 30 centimeters above the top of the conduit. Care should be exercised to compact thorougNy the backfill under the haunches of the conduit.
7.
For that portion above the trench on each side of the conduit pipe, the width of backfill is equal to twice the diameter of the conduit or 3.50 msters whichever is smaller. After being bedded and backfilled, all conduits are protected by cover fill 1.00 meter high, before any heavy equipment is permitted to cross during the construction of
Drainage and Slope Protection
through shop elongation or by means of jacks applied after the entire line of conduit installed on the bedding but before backfilling. The vertical elongation should be maintained by means of sills and struts, or by horizontal ties used on paved invert pipe. Pipes and struts should be 30 centimeters in place until the embankment is completed and compacted.
Methods of Measurement Conduit pipe of different types and sizes whether new or reinstalled will be measured by linear meter installed. Conduit with sloped or skewed ends will be measured along the invert. Every section will be measured according to the number of units installed. Class B bedding (footing) materials placed and approved will be measured in place by cubic meter. When the Bid Schedule contains an estimated quantity for furnishing and placi4g backfill materials and pipe culverts, the quantity to be paid will be ttre number of cubic meter completed
in place and accepted, measured in final position between the limits as follows:
1.
Measursment include backfill materials up to the top of the original ground line but will not include any materials placed outside of vertical plane 45 cni. up outside and parallel with the inside wall of the pipe at its widest hori-
2.
The measurement will also include all backfill materials above the original ground line adjacent to the pipe for a height of 30 cm. above the top of the pipe and for a distance on each side of the pipe not greater than the widest horizontal dimension of the pipe if the original ground line is less than 30 centimsters. The measuremertt includes the placing of backfill materials in all trenches.
the roadway"
Field Strutting Whenever required by the plan and specifications, vertical diameter of rounded flexible conduits is increased by 5 percent
3.
zontal dimension.
Elements of Roads and Highways
6-8 Design of Underdrain Underdrain is categorized under Item 501 of DPWH Standard Specifications, which provides that:
"This item shall consist of constructing underdrain, using pipes and granular filter material underdrain pipe outlets and blind drains using granular material in accordance with the specifications and in reasonably close conformity with the lines and grades shown on the plans or as established by the engineer."
l. 2. 3. 4. 5.
The pipe is used to carry away collected water. The size and number of pipes and its locations of opening should be studied carefirlly to prevent excessive entrance velocrlv that will cause silting to the pipe. Filter materials with which the trench is backfilled or the opening in the filter, should be fine enough so that the adjacent soil will not be washed-out into the drain. The top of underdrain should be sealed with impervious soil to prevent the entrance of surface water. Intercepting drains must extend into the impervious zone. The pipes are laid with the flow line at least 1.20 meters below the finished grade and carefully bedded with gravel or filter materials.
Drainage and Slope Protection
5. 6.
acceptance.
Construction Requirements
l.
2. 3.
Materials should conform with the requirements specified as follows:
5.
2. 3. 4. 190
(AASfilO
Granular backfill filter materials shall be permeable meeting the requirements of AASHIO M-6 specifications except that soundness tests will not be required and minor variations in gradrng and content of deleterious substances may be approved by the engineer. All materials are subject to inspection before
4.
Zrnc coatd, (galvanized) comrgated iron or steel for culverts and underdrain (AASFIIO M-36). Extra strength and standard strength clay pipe and perforated clay pipe (AASHTO M-165) Porous concrste (AASI{TO M-176 Perforated concrste (AASIfIO M-175)
M-I77)
Asbestos cement perforated underdrain pipes M-189
Granular Backfill Filter Materials
Materials
L
Bituminous fiber non-pressure sewer drain and under drainage pipe system (AASSHTO
6.
Pipe installation. Trenches are excavated to ttre dimensions and grades required by the plan. A minimum of l5cm. bedding layer of granular backfill materials are placed and compacted at the bottom of the trench. Subdrainage pipe are embedded finnly on the bedding. Perforated pipes are placed with the perforations downward securely ed with appropriate fittings or bands. Non-perforated pipes are laid with the bell end upgrade with open ts wrapped with suitable material to permit entry of water, or unwrapped as may be specified. Upgrade end sections of all sub-drainage pipe installations are closed with suitable plWS to prevsnt entry of soil materials.
After the pipe installation, granular backfill materials are placed 30 centimsters above the top of the pipe and should not be displaced by the covering of open ts. The remainder of granular backfill are placed and compacted at every aft€r 15 cm. layers up to the required height. Any remaining portion of the trench above t}re granular backfill shall be filled with either granular or impervious material and thoroughly compacted.
l9l
Elements of Roads and Highways
Drainage and Slope Protection
Underdrain Outlet
6-10 The l,egal Aspect of Drainage
Trench for underdrain outlets are excavated to the depth and width as planned. Pipes are laid in the trench with all ends firmly ed and backfilled after inspection and approval of the
Flighway agency is legally responsible for any damage tcr private property affected by the changes it makes in natura! drainage pattem within the limit that water must flow.
pipe installation.
Blind Drain Trenches for blind drains are excavated to the width and depth as shown on plans. The trench is then filled with granular backfill material to the required depth. Any remaining upper
portions of the trench should be filled with either granular or impervious material in accordance with the requirements for
Damage claim against the Department could be established
1.
Wren as a result of the agency's project, the flow of several streams or creeks were concentrated into a single channel that resulted to erosion, silting or flooding ofpri-
2.
When due to poor design or inadequate rnaintenance rel="nofollow"> water backed against highway or embankment resulted to rnundation of land or property or caused irjury or death. Liabilrty however, is limited to damages lr direct conscquences of the improvement. The agency would not be li-
excavations.
6-9 Debris Control
3.
Flood waters usually carries objectionable objects like brushes, banana trunks, tree branches etc. These floating debris clogs culvert entrances and raise the headwater elevation overflowing the road and damaging ading properties. Culverts should be designed to allow debris to A single large span box culvert is preferred on streams carryrng large floating objects than the multispan culvert with the same area of openings.
Another alternative is to extend the curtain wall separating the barrels of the multi span culverts upstream, with its top slanting downward so that in time of flood, debris carried by flood water will ride up on this wall or turn to easily tluough the opening. Another method proven effective is to install up stream debris racks or wire, steel rail or piling. Some design provides trap for the sand or gravel carried by the stream rather than having it tlrough the stmcture. However, design of debris control devices depards upon the kind of debris to be handled, the volume of floodwater and the site conditions. 192
if:
4.
vate properb/.
able for damages if an unprecedented storm causes the stream to overflow a newly constructed channel, provided that this channel has the capacity equal to the natural volume of water flow. Engrneering decisions if based on an accepted practice, do not provide for a course ofaction. ln any case, the responsibility of the highway agency would be determineil through negotiations or court litigations. 'fherefore, design of drainage system must satis$ the various requirements of the environmental laws and regulations.
6-ll Roadway Design and Construction for Unusual Soil Conditions Problems usually encountered
in the design and construc-
tions of roadways are:
l. The stability of fill sand slope 4. Permafrost 2. T\e drainage 5. Elasticity and rutting 3. Capillarity and frost heave 193
Drainage and Slope Protection
Elements.of Roads and Highways
Stability of Fills and Slope
Original fill sloPe Slip surface
There are instances where the materials in cut bank slips down the roadway, or sometimes, a portion of high fill slides outward carryrng portion of the roadway. This pattem of failure is common in fills or cut slope of homogenous non-granular materials.
1. 2.
3.
4. 5.
Slides may happen during construction or at later date after the road is in service. It is advisable to risk some sliding or adjustments of large slope than to flatten increasing pay yardage. If possible during the location surveys, areas that are threatened by frequent slide, shc'uld be avoided. Minor slope adjustment, slides, and ledge falls that occur during construction should be removed to widen filI or to flatten the slope.
Slides may be caused either by mudflows, slope adjustment, or movement due to underground water or undercut rock strata. Slides happened when an underlying inclined surface of shale, soapstone, or the like is lubricated by seepage water.
Slides mayte controlled by removing large portion of the materials above the slippage surface, or by some drainage devices that keeps water offthe surface of weakness. Water must always be intercepted before it lubricates the critical slip surface.
Surf,ace of shear failure
Common Failure
FIGURE 6-8 COMMON FAILURE OF SLOPE
Capillarity Capillarity is the tendency of water to seek its own level as
if in an open channel flows through the pores a:rd fine channels of the soil. It is the force pulling free water through the voids of the soil in all directions.
Capillary action is most common in permeable rnaterials such as dirty gravel and soils composed mainly of fine sand" silts or clayey silts. Capillary flow however, is less common in impermeable materials like clay and colloidal soils.
L ln roadway
construction, moisture has to be controllerl. Over saturation of the soil in road structure reduces its
strength and the differential expansion of the soil due to uncontrolled moisture may lead to serious problerns. 2.
Original topography J.
F'IGURE
t94
6.7 MAN MADE SLOPE OF NEW SHAPES
Slumping of Fill
Moisture in the roadway is brought about by the changes in weather, seasons or by capillary action of the water. Water movement due to capillarity action take place in any directions, and an upward movement may create undesirable conditions. If the surface of the soil is open, evaporation of moisture is faster, and no damage may result, bug if the surface is covered with pavement or other impervious blanket, capillary water may accumulate and saturate the subsurface layers that usually resulted to pavement failure.
l9_s
Drainage and Slope Protection
Elements of R.oacis and tr{ighways 4.
5.
Consistency of soil .zaries fiorn semi solid to plastic irquid if moisture content is increased. The behavior of the material used is directly correlated with changes and percentages of moisture content. Voids in soils are of the same order of magnitude as the particle sizes. Thus, the height of capillary rise would be greater in fine grain soils than in coarse grain soils. Likewise, temperature piays an irnportant role in the capillary
Highly plastic soils should not be placed closer to
a L.
When heary loads itjs on a plastic soils, compression and rebormci occurs to at least 6 meters below the surface. B0% of tlre load is concentrated 90 cm. from the top of the surface. The design therefore, is to sum up the total expected load and rebound in the pavement to be sure that it does not produce fat.igue and failure in the pavement.
rise r:f water in soils. 'Ihe height of rise is gieater in low te.rnperature than in high tenaperaflire.
-
Deflection of the pavement surfbce as the wheel slowll' rolls past dre reference pornt is measured by a measuring device called Bankelman Bearn. A long slender bar slips into the space between the dual tires of the truck wheels. Deflection rate of travel shock wave is recorded.
TABLE 6-4 REPRXSENTATIVE IIXIGHTS OF
CAPILLARY RISE IN SOILS
Apgoximate Capillary Hei ehts Soii Tlpe Small grar,el Coarse sand Fine sand Silr Clay
Centimeters
Feet
2to l0
0.1to 0.4
15
0.5
30 to 100 100 to 1000 1000 to 3000
3to30
the
roadway surface where heavy loads are ex?ected. Early cracking of the pavement may happen due ro deformations caused by tlie rebound of the soil.
6-12 Stabilizing the Unsuppofred Slope
Ito3 30 to 90
An existing earth slope ihat have been stable can experience significant movement called slope failure or landslide due to the following physical changes :
TABLE 6.5 REPRESENTATIVE VALUES OF COMPRESSIVE STRESSES RESIILTING FROM CAPILI"ARY T'ORCES
a. Changes in natural conditions b. Changes induced by man Changes in natural conditions may be the result from:
200 to 2000 2000 to 6000
0.i to
1"0
1.0 to 3.0
l0 to
100
100 to 300
Elasticity and Rutting Elasticity is common in soils whose fines consist mainly of flat and flaky particles. This kind of soil has rubberized characteristic that rebound under heavy loads.
t96
l. Ocgurrence ofearthquake. 2. Subsidence ofunderground cavern. 3. Erosion. 4. Slope weakening due to the development 5. 6.
of cracks or urtrusions. by water shnnkage cracks that are followed Variations in the elevation of ground water or changes in
the slope subsurface flow that create new seepage forces. Weakening of buried soil or rock seams due to ground water flow or chemical leachine. 197
Blements of Roads and HighwaYs
Drainage and Slope Protection
Changes Induced by Man Grr
a.
b. c"
d.
Increased loading on a slope or near its crest. Removal of earth below the toe of a slope. Removal of materials from slope making it steeper. Topographic modification like earth moving, excavations, change in elevation from one areato another which may create slope failure. Landslide or other conditions caused by manSlope and Toe Failure typical for possessing internal friction
Slide Slide refers to the occurrence where the moving mass is defined and separated from the underlying and adjacent earth by
plane, comprising a number of adjacent planes were seepage result The seepage plane represent the continuous surface where the maximum shear strength of the earth material has been reached with the result that large displacement occurs.
Slide is classified into four:
l. 2. 3. 4.
Rotational slide. Translational slide. Block or wedge failure.
Base Failure typical for clay slopes underdrain by deep, hard stratum.
Flows and spread.
CofnAG-flto-
Ratioiral slide is associated with natural slopes and constructed embankment of homogeneous materials possessing cohesion.
Translational slide is associated with slope of layered materials where the mechanism of slippage occurs along a weak plane that possesses a downward dip and in cohesionless soil slopes where seepage occurs.
Block or Wedge'failure refers to the displacement of an intact rnass of soil due to the action ofan adiaccnt zone ofearth. l9l{
FIGURE
6.9 RATIONAL SLIDE 199
Elements of Roads and Highways
Drainage and Slope Protection
Firm clay Sofr clay with water bearing silt and sand layers Ftrm ctayey
FIGURE 6-10 TRANSLATIO\AL SLIDE
Flows and Spread failure is the nrost complex type of soil mass nlovement. Flow involves lateral rnoveJnent of soil having a clnractcrrstic uf viscous fluid, although the actual consistency of the moving mass may vary fiom very wet to dry. Spread refers to the occurrence of rnulti-directiorral lateral movement bv a fractured soil mass. Earthquake is a typical causes of lat*rai spreads.
Depositional area
-t^
FIGURE 6-12 FLOWS AND SPREAD FAILURE
6-13 Improving the Stabitity of Slope Slope areas that have experienced slides in the past should be considered likely to undergo further movement if loading
condition changes. FIGURE 6.1
2{Xl
1
BLOCK ANO WEDGE SLIDH
201
Drainage and SloPe Protection
Elements of Roads and Highways Procedures adopted in the past which have been successful in stabilizing slopes are enumerated as follows:
l. 2. 3.
Corrective and preventive measures of reducing a mass or loading have successfully prevented further slides. Improving the shear strength of the earth in the failure zone by constructing structural elements that will provide resistance to movement.
11.
Pile Driving, sheet piling or retaining walls are utilized to provide lateral and increase resistance of slope
tending to stocks. t2 Improvement and protective methods such as slope flattening and drainage control are preferred for economical reasons.
Consider the characteristics of the soil in the slope like:
a)
The thickness and depth of the materials involved in sliding. b) The ground water conditions. c) The spaces available to undertake corrective changes. d) The topographical conditions at the vicinity of the slope and the tendency for changes such as the advert of the seismic and vibratory loadings to occur. 4. 5.
Slope llattened or benched
Where area is available, flattening of the slop can be done to reduce the weight of the mass that tends to slide. If base failure is anticipated, placement of beam below the toe of the slope
6.
a.
will increase movement resistance.
lf the zone below the toe is susceptible to severe erosion, protective rock fill blanket and riprap catr be installed at the toe area.
7. To prevent infiltration,
b. Berm provided at toe
erosion and to reduce seepage force, the stone subsurface water and intercept surface water should be lowered.
8.
If the soil is cohesionless, the shear strength of the slope material can be improved ttrrough densification by using explosives or vibroflotation or terra probe procedures. For cohesive soils, shear strength could be improved by consolidation and water content reduction through surcharging which may include wick drains, electro osmosis and thermal drytng
10.
add cementing and bonding agent.
202
c.
Protection against erosion provided at toe
Where the weak condition is critical to the stability of the slope, grouting and injection methods could be utilized to FIGURE 6-
13 IMPROVING THE SLOPE STABILITY
203
I I I
i
Elernents of Roads and Highways
1. Drive pile closest to stope, then
2. Drive back piles last to reduce effects of driving on slope stability
d.
Provrde driven or cast in place piles
Lowered water
e.
table
Drainage and Slope Protection Settlement and distortion of a retaining wall due to compression of the foundation soil must be limited to a tolerable value. The combined effect of soil and water pressure on the retaining wall causes over turning moments and sliding forces greater than the condition where there is no water. To avoid the rise of water building up behind the retaining wall, a weep hole or collector drainage system or both ilre provided as part of the design construction. Weep holes should be at least 3 inches diameter provided with granular soil filter fabric at the wall to prevent backfill erosion. The horizontal spacing of weep holes ranges from 1.20 to 3.00 meters. For taller walls, two or more rows of weep holes may be provided with typical vertical spacing at l.50 msters.
Col,ector drahl perforated pipe in gravelfilter
Lowering ground water table to reduce pore pressure in the slope Removed soil
2:tltlm. plumb
Fill SloPe or
--f
.075 to .10 Weepl.bles
@ 1.50m. o.c.
: ' Ground FIGURE
6.14 IMPROVING THE SLOPE STABILITY
line
30x30x30 Gravel bacKill
6-14 Retaining Wall The practical use of gravity retalning wall is controlled by height limitations. Thus, the required wall cross section increases signlficantly with tall heights due to the effect of the triangular soil pressure distributed behind the retaining wall. If the ground water level rises into the backfill behind a retaining wall because of either changrng ground water condition or percolating water surface, the lateral pressure against the wall is also changed.
204
]x+o.om Dry Rubble
Cement Rubble
FIGURE 6-15 CROSS SECTION OF RUBBLE RETAINING WALL
205
Elements of Roads and Highways
Drainage and Slope Protection 1n"
0F-F-1 L- ls" -l
(a) Stralght Sectlons Used where tension valve of inter lock is cellular construction Piling ordered with required interlock strength specified and type of structure indicated Gravity wall
FIGURE
1n"
i-11R2"
b-F-r L-
i6"-J
Cantilever wall
6.16 REINFORCED CONCRETE RETAINING WALL
(b)
Z
Sec0ons
High ratio of beam strength to weight means maximum economy in steelsheet piling. Used primarily in filled bulkheads or other walls requiring high beam strength.
(c) Archweb Sectlons Designed for applications where Weep Hoeg 3 to 4'y' spac€d at 1.50 m. o.c.
Gravgl or Ftter Fabdc
a combination of beam strength and interlock tighness is required. Used generally in light bulkheads internally braced single wall
cofferdams, cut-ofi wall s.
FIGURE
206
7 DRAINAGE METJHODS TO PREVENT DEVELOPMENT OF WATER PRESSURE BEHIND THE RETAINING WALL
6-1
FIGURE 6-18 REPRESENTATIVE STEEL SHEETING SECTIONS
Drainage and Slope Protection
Elements of Roads and Highways
A good retaining wall
design must conform to the following
Excavation and Placing
requirements:
l.
The base and stem of the retaining wall must be capable of resisting the internal shear and bending moments developing as a result of soil and other loading.
2. 3. 4.
The wall must be safe against overturning. The wall structure must be safe against sliding.
The bearing capacrty of the foundation material ing the wall must not be exceeded.
Item 504 Rip Rap and Grouted Rip Rap This item includes furnishing and placing of riprap with or without grout; rvith or without filter backing. Stones for riprap shall consist of rocks as nearly rectangular in section as is practical except that riprap of Class A may consist of round natural stones. The stone shall be sound, tough, durable, dense, resistance to the action of air and water and suitable in all respects for the purpose intended. Class of Stone for Ripraping Class
A
- Stone ranging from 15 to 25 kg. with at least 50olo of the stones weighing more than 20 kilograms.
Class B
- Stone ranging from 30 to 70 kg. with at least 50%
The bed for riprap is excavated dorvn the requir*d depth properly compacted, trimmed and shaped. The riprap foundatio:r is dug below the depth of scour. The toe trench is filled with stone of the same class as specified. Stones placed below the water line are distributed properly and those above the water level are placed by hand or individually laid by machine with close broken ts firmly bedded into the slope against the ading stones
Each stone is laid with its longest axis perpendicular to the slope in close with adjacent stone. The riprap is thoroughly rammed into place and the finished stone are laid to an even tight surface. lntersections between stones are filled rvrth small broken fragments firrnly rammed into place"
Grouting When grouted riprap is specified, stones are placed by hand or individually laid by machine. Spaces between stones are then filled with cement mortar sufficient enough to completely fill all the voids exceptthe face surface ofthe stones left exposed.
Cement groufijs placed starting from the bottom to the top of the surface and then swept with stiff broom. After grouting, the surface is cured like structural concrete for a period of at least 3 days after the installation.
of the stones weighing more than 50 kilograms.
Class C
- Stones ranging from 60 to 10Q kg. with at least 50% of the stones weighing more than 80 kilograms.
Class D
-
Stones weighing from 100 kg. to 200 kg. with at least 50% of the stones weighing more than 150 kg
Where required, riprap shall be placed on a filtered layer to prevent fine embankment materials from being washout through the voids of the face stones. 208
Mrsonry stone is categorized under ltem 505 of the DPWH standard ipecifications. This item consists of stone masonrf in minor structures, in headwalls for culverts and raaining walls at the toes of the slope.
Material Requirements
1.
The stone should be clean, hard and durable. Adobe stone shall not be used unless specified. 209
Drainage and Slope Protection
Elements of Roads and Highways the backing by 30 centimeters minimum.
Item 506 Hand Laid Rock Emtrankment
Z.
When the wall thickness is 45 cm. or less, the header should extend entirely from the front to the back face.
Material Requirements
3.
Backings are built chiefly of large stones. The individual stones of backing and hearting are well bonded with the
Stones for hand laid rock embankment must be sound and durable furnished in a well balance range of sizes meeting the requirements as follows:
face wall and with each ottter.
4. All
openings and interstices in the backing are filled ccmpletely with cement mortar or with spall surrounded completely with mortar.
All stones should be more than 0.015 cubic meter in volume and not less than 75 percent of the total volume should consist of stones at 0.03 cubic meters in volume. Stones obtained from excavation performed under the
I
Pointing and Coping
contract may be used.
Adobe stone should not be used unless otherwise specified in the plan.
Cement mor[ar for ts on top of masonry surface are crowned slightly at the center to provide drainage. If coping is required, it should be indicated in the plan.
Where coping is not required, the top of the wall is finished witlr stone wide enough to cover the top of the wall from 45 cm. to 100 cm. in length and of random heighs of 15 cm. Stone is laid where the top course is an integral part of the wall. The tops of the top course stone are pitched to line in both vertical
Construction Requirements. Excavation shall be sufficient enough to expose the foundation bed. Stones are laid flat securely placed with their broken t lined. The larger stone should be generally located in the lower portion of the structlrre and voiCs eliminated to possible
2.
and horizontal plane.
Weeping Holes
All walls and abutrnents
extent.
Spall smaller than the minimum stone size are used to
3.
should be provided with weep holes placed at the lowest point where free outlets for water can be obtained and spaced not more thart2 meters center distance.
4.
Cleaning and Curing
5.
check the larger stones solidly in position to fill voids between the major stones laid in the embankment.
The exposed face of the rock mass should be uniform without projections of more than 15 cm. beyond the neat lines indicated on plans.
Backfill adjacent to the hand laid rock
embankment should be filled entirely with acceptable materials coming from the excavation iterns and compacted.
Immediately after laying and while the mortar is still fresh, should be thoroughly cleaned of mortar stains and should be kept clean until the work is complded. If weather is hot or dry, the masonry should be protected from the sun and kep wet for a period of at least 3 days after
Itern 5-7 Sheet Piles
the completion.
sheet
all face stones
212
This item consists of furnishing dividing and cutting off of piling covered by the specifications: 713
Drainage and Slope Protection
Elements of Roads and HighwaYs
Material Requirements
l.
Timber sheet pile may consist of any species that will satisfactorily stand driving It is sawn or hewn with square corners free from worn holes, loose knots, wind rhuk.., decay or unsound portions or other defects that might impair its strength or tightness.
Z.
Concrete Sheet Piles. Concrete reinforcement and marrufacture of concrete sheet piles should conform to the requirements of ltem 400 - Piling.
3.
SGaI STeelt-Pites sFould be of the type, weight and section modulus indicated on the plans or special provisions and conform to the requirements of item 400- piling.
Item 509 Gabion Gabion is a wire mish supplied in various width and length that is in multiple of 2,3,or 4 times its width. The height is equal to 1.2 or 1.3 the horizontal width equal to 100 centimeters with a tolerance limit of 3%o. The wire mesh is made of galvanized steel or plastic having a minimum size of 3.05 mm diameter. Its tensile strength should be in the range of 423.7- 686 Mpa
Construction Requirements
l. The wire mesh is twisted to form hexagonal opening of uniform sizes. The maximum linear dimension of the mesh opening shall not exceed 11 mm and the area of the mesh opening do not exceed 51.65 square msters. 2. The mesh should be non-raveling which means the ability to resist pulling apart at any ofthe trvists or connection when a single wire strand in a section is cut. 3. That the Gabions sides, ends, lid and diaphragms can be assembled at the construction site into rectangular baskets of the specified sizes. It should be of single unit constnrction. The base, lids" ends and sides should be either woven into a single unit or one edge of those connected to the base section of the gabion. 4. That Gabions could be divided equally by diaphragms of the same gauge as the body of the gabions into cells the length of which does not exceed the horizontal width. All perimeters of the edges of the mess forming the gabion should be securely seivedge so that by q'tng the selvedges the ts shouid have at least the same strength as the body ofthe mesh. 6.
60,000 - 85,000 psi.
For galvanized wire mesh, the minimum zinc coating should be 22.7 gru*r per 0.0929 mt 10.t0 o/sq. ft) of uncoated wire surface as determined by tests conducted in accordance with AASFNO T-65.
in
gabions are hard, durable rock pieces that will not deteriorate when submerged in water or exposed to seRocks used
vere weather conditions. Rock pieces should be uniformly graded generally in sizes ranging from 10 to 20 centimeters. FiU"O gaUiont thull have a minimum density of 1,400 kg/nt' and voids distributed evenly. The rock shall meet the requirements of AASHTO M-63 except that the sodium sulfate soundness loss should not exceed 99/o after 5 cycles. ')1,4
The tie and connection wire should be supplied in sufficient quantity to securely fasten all edges of the gabion and diaphragms and to provide for four cross corurecting wire in each cell whose height is l./3 or Yzthe width of the gabion and 8 connecting wires in each cell whose height equals the width of the gabion.
6-15 Highway Bridges HighwaV bridges are of two types:
1. 2.
Those that carry vehicular large stream.
traffic and pedestrians over
a
Those that separate traffic movements as interchanges and street pedestrians over or under crossings.
2lt
Drainage and Slope protection
Elements of Roads and ftrighways
tlydraulic Problerns
l.
There must be available strearn record that provides the usual method of estimating water discharges under the bridge.
2.
,A,nalysis of the channel relationship as to:
a. b. c. _t,
Peakflow Water way opening Water surface elevation at the structure and upstream and flow velocity.
Highway Bridges, Designed to Resist Loads Brought by:
l. 2.
The weight of the structure itself called'dead load.
3.
The weight and dynamic effect of moving load called "Live Load". The centrifugal forces developed by moving vehicles on
4.
curved structure. The wind load and the stresses brought about by:
e. Rib shortening
a.
f.
b.
Erection
flurrent+rsssus
h.
d.
The degree of confiaction of the flowing water in the
Earttquake
channel approach. +.
Final structure proportions and required channel modifications based on the studies.
5.
6.
Etfect of bridge opening and approaches that might cause flood to adjacent properties. This is associated with hydrauhc aspects ofbridge design. Econondc, legal and social implications where coopera-
tive planning with all affected groups and agencies is ry
8.
to
A bridge consists of substructure of abutments and piers that s superstrusture that carry the roadway between s. Bridge fype includes: slab, girder, truss, arch and cable stayed. Each suspension bridge has a distinctive form of structure, the selection of the kind of bridge to be installed depends on the length of individual span as follows:
necessary.
1.
Where the bridge is to rest on eroding streambed scouring is the primary concern. The problem of the designer is, if the design is over safe, it is over design, meaning, the foundation becomes very costly. But if scouring is under estimated, the foundation might be undermined which might result to total destruction of the entire bridge.
2.
Recent findings showed that the latest scours is when the pier has less resistance to flow. Meaning, that the piers are aligned with the flow rvith the smallest cross section that is best where scouring is a problem. Test results fruther showed that, scouring increases wilh depth of flow and becomes a problem in streams with high ratio bet$,een flood and normal flow
2
Bridge Types
3. 4.
Short span up to 18 meters which either: a.) Reinforced concrete rigid frame with slab deck. b.) T-Beam or box girders reinforced concrste. c.) Steel plate girders with reinforced concrete deck. Bridge of large span a.) Girder type rigid frames of reinforced concrete. b.) T-Beam or box girder reinforced concrste. c.) Steel plate girders with reinforced concrete deck Span that exceeds 90 meters long steel trusses, arches of steel or reinforced concrete. Span that exceed 150 meters are generally made of steel trusses, cable-stayed or suspension bridge.
For deg purposes, AASHTO has adopted vehicles as representative loadings
standard
:
2r7
Elements of Roads and Highways
CHAPTBR I Not less than 9.0O meterE
At least 18.30 m. greater than appmach pavement
Face of wall or pier
Face
of lltwAll
CONSTRUCTING THE ROADBED
Face of rail
7-l Roadway.60 m. min. ureater than approach way but not le6s than 7.30 m.
TUNNET ANO BRIDGES
UNDERES
Soil as Structure
Early road constructions have concentrated mainiy on the road surface pavement. Little attention was given to the subgrade, the base materials, and the manner of construction more particularly, tlre placing and compacting of the pavement foundation. As a result, too many road failures past and present were recorded with an endless maintenance and rehabilitation activities.
F IG
uRE&
1
e
R
Ec
oMM. -
"R
H
Xrrffiinr^AtD
o
R
rzo NTAL c LEARAN c E
For design pu{poses AASFfIO adopted standard vehicles that produce a representative loadings. HS 20-40 designation is a truck semi-trailer combination havrng a total weight of 36 tons. Trucks and other heavy equipment that contribute to the larger live loads has variety of total werght, axle loads and axle spacing. The number 40 indicates the year in which the loading standard was adopted. For minor highways, the standard vehicles are trucks weighing 20 tons(H-20) 15 tons (H-15) and l0 tons (FI-I0)
Because of these very expensive undertakings, hrghway agencies were prompted to undertake advance researches and studies on the properties of sub-grade and soil performance under severe conditions. After a long study of the unending road failures, road agencies have established a more detailed procedure regarding the kind of materials to be used on a particular condition, type and behavior of the soil where the road is to be constructed. Roadway has three major structural parts, namely:
l. Tlie Sub-grade or Sub-base 2. 3.
The Base Courso The Pavement
'The Sub-grade or Sub-Base is the earth beneath the road, properly arranged and graded, compacted and stabilized. It is defined as the "ing structure on which the pavement surface and its special under-courses rest. " In a cut section ofa road, the sub-grade is the original soil 218
219
Elernents of Roads and Highways
Constructing the Roadbed
lying below the layers designated as the base and sub base materials. On fill road sections, sub-grade consists of the imported materials taken from nearby roadway cuts or fiom borrow pit.
Construction and Maintenance Requirements of Untreated Gravel Road Surface
The Base Course is the materials laid on top of the subgrade consisting of crushed stone or gravel, sometimes mixed with asphalt binders. The Pavement is the material laid o'zer the base coarse consisting of Asphalt Concrete or Portland Cement Concrete.
FIGURE
7.1 ROADWAY STRUCTURE LONGITUDINAL SECTION
7-2 Types of Base Course Base course is classified into trruo t)?es:
l. 2.
The granular base course or untreated soil mixture. Treated base course.
l. That, the road must be stable to the super imposed loads without detrimental deformation. It must be resistant against various traffic activities and could withstand the abrasive action of traffrc. 2 It must shed the large portion of rain that falls on the surface because water penetrating the sub grade might soften it and loosen the surface stability. It must be free frorn large rocks or stones over one inch in diameter so that it could be regularly maintained by btading or dragging. 4. Gravel road must possess capillarity properties sufficient enough to replace the moisture lost through the surface evaporation. The road must maintain the desired damp condition that is required to bind the particles together. 5. On dry weather, the moisture film on the clay particles should bind the entire mass together, and in wet weather, the first rain that fall on the surface, should expand the clay and close the pores to prevent water from entering
6. 7. 8.
The granular base course is a road surface ofuntreated soil mixture described as gravel road. Gravel road consist largely of stone pebbles or crushed rock particles combined with either; clay, lime, iron oxide or other fine materials sufficient enough to serve as binder of the coarse particles. 220
L
If
and softening the materials.
An excessive amount of highly expansive clay materials should be avoided because clay will swell and unseat the coarser materials when wet and ultimately will weaken the stability ofthe road. Gravel road must be low cost. Funds for low traffic road is very limited that most of the time overlooked in the list ofappropriation priorities except on election period. Use local materials. Meaning, those materials that could be found nearby the project must be utilized.
the gravel surface road is to be maintained for several
years without bituminous or asphalt surface treatment or other
impervious surfacing, AASHTO standard specifications requires maximum liquid limit of 35 and a Plastic lndex of 4 to 9 and a maximumS%o ing the No. 200 sieve. 221
El3lents
3!
Roads and.Highways
Constructing the Roadbed
TABLE 7-1 GRADING REQTIIREMENTS FOR SOIL AGGREGATE MATERHLS (AASHTO Designation M-f47)
l. z.
to specified temperature and mixed with
Percentage by Weight ing Square Mesh Sieve Sieve Dcsig
mm Inch 150 2u 25 I' l0 318" 4.75 2.00
No.4 No. l0
0.425 No.40 0
075 No.200
Grading
Grading Grading Grading Grading Grading
DEF
BC
A
100 30-6s
75-95
100
100
4U75
50-85
6G100
25-55 300-60 15-40 204,5 80-20 lt30
2-8
5-20
100
100
35-65 50-85 55-lm 70-100 25-50 40-70 4G100 55-100 15-30 2545 2G50 30-70
5-15 5-20 5-20
8-25
Suitable for Surface Courses
Suitable for Basc and Sub-bases
To stabilize the base coarse. it is
either; Asphalt
Cemen! Cutback asphalt or Emulsion asphalt. The qualrty of asphalt is classified as either for stabilizing or for waterproofing purposes only. If the purpose is for stability, mixhrres are measured in the laboratory by the Marshall or FWEEM Stabilometer procedures. The weigirt of asphalt in percentage would
probablyintherange of 5Yoto1o 5. If the purpose is for waterproofing only, 2o/o to 3yo of the asphalt binder is added. 6. If Emulsion asphalt is used, enough water is included in the mixture to allow compaction at near optimum moisture content. .
Sand and Asphalt Base Course
7-3 Treated Base Course sometimes treated with
either Asphalt, Lime, Portland Cement or other materials as binders mixed with the aggregate base course. Treated base course is adopted if in the study or analysis of the highway agency, a better road can be produced at a minimal over all cos! or when a politician order the lughway office to construct the road with or without study because it was a commitment durtng the campaign period.
Asphalt or bituminous treatment is employed to waterproof and bind the granular aggregate to the sand and clay. Thus, the primary function of the asphalt in a treated aggregate, is waterproofing. Asphalt treated base allows a thinner over all depth of the pat'ement. Different types of asphalt are used to bind the natural materials like untreated granular base and granular aggregate with sands and even clay. The type ofasphalt binders for base course depends on several factors enumerated as follows: 222
J4.
100
The mixing procedure is either by plant or field mixing. If mixing is processed in the plant, the aggregate is heated
The sand and asphalt base course is composed of either, pit or river sand cemented wittr asphalt materials. In the early road construction, sand and clay rnixture is not only used as road surfaces but also for base courses. But lately, the Cutback asphalt, Emulsified asphalt or Tars have been introduced as substitute for the clay binders to produce loose beach sand, dune
quallty base courses for roads and highways. Sand for rmxing asphalt should be clean and strong, because the surface properties and grain shape must have the qualrty to resist displacement under load. If in the eveirt that quality of available sand is not satisfactory, it may be blended with sharp angular particles like crushed aggtegate, stone or screened slag, stone dust, loess, cement or other non-cohesive minerals to produce an stable mixture. The test could be by the Hubbard Field, Marshall and Hveem Stabilometer procedures.
Asphalt binders with the grade of asphalt cerneNil for hot plant mixing should be:
223
Constructing the
Elements of Roads and Highways
a.) Medium viscosity, rapid or medium curing asphalts. b.) Slow setting emulsified asphalt or c.) Tars of grade RT-6 to RT-10. The content of asphalt binder is in percent by weight ranging from 4oA tn l0%. Compaction is done using either pneumatic tired or smooth wheeled roller. In case the surface is tight and non-friable, sealing could be disregarded.
Fine Grain Asphalt Base An asphalt stabilized base and sub-grade constructed with fine grained has- a controlled Plastic lndex of 6 to l0 respectively. Aggregates with Plasticity lndex up to 30 are processed with lime. Those with up to 50o/o ing the No. 200 sieve and Plastic lndex up to 18 can be stabilized even without pretreatrnent.
Soil and Base Course Stabilized with Cement The use of Portland cement in stabilizing soils and aggreWar-l in 1914.
gates was initially practiced after World
1.
2.
3.
224
Cement stabilization by mixing natural materials and Portland cement compacted at optimum moisture content and cured to hydrate the cement is considerably strong and stable base. It is less susceptible to deformation caused by moisture and temperature changes. Comparatively, this is less rigid than the Portland cement concrete because its modulus of elasticity ranges from 100,000 for clay soils with little cement up to 1,000,000 for the strong mixture. Its compressive strength ranges from 300 psi to 600 psi with flexural strength of about 20o/o of the compressive value.
Portland cement concrgte modulus of elasticity ranges from 3 million to 6 million with compressive strength of about 3,000 to 5,000 psi.
R
oadbed
The stabilized cement mixture is called "Soil Cemenl" produced by using abundant native local materials subdivided rnto three types:
1.
Sandy and gravelly soils contarning less than 25o/o sllt and clay.
2.
Sand with lesser amount of fines like beach sand, glacial
3.
and windblown sand. Silty and Clayey Soils.
Materials having plasticity index greater than 30 is rarely used, unless lime is added. Materials with high PH or sulfate content are not advisable for use. The cement content fbr stabi" lized mixture ranges from 5o/o to l4Yo by volume of 3o/oto l6oh by weight of dry aggregates. Sandy and gravelly soils required less amount of cement, unlike the silt-v and clayey soils that needs higher percentage of cement. The dry densities of cement stabilize mixture compacted b1' AASI{|O standard methods, ranges from 135 lb per cubic fbot for a well graded gravel down to 85 lb. per cubic foot for silty or clayey soils, the recommended field density is about 95olo. The qualitS' of aggregate cement mixture is measured by its abilrty to resist abrasion and disintegration. Other methods of testing for stabilize cement content is the Unconfined and Triaxial Compression and Flexure Tests.
z-+ Grading and Maintenance of Untreated
Surface The cross slope of untreated surface gravel road must be sufficient enough to drain water to prevent potholes and softening of the roadway, thus;
1. If
the road materials are sufficiently stable and water tight, one inch per slope is considered satisfactory although 3/8 ta Yz" peer foot slope is prefi:rred. 225
Constructing the Roadbed
Elements of Roads and HighwaYs
2.
Ifthe road is steep grade, substantial cross slope is needed
5.
to direct the water into the roadside.
Compaction is effectively done by using pneumatic tired or steel wheeled rollers. Where surface is tight and nonvariable, sealing may be omitted.
Untreated surface road is seldom constructed in less than 20 ce.ntimeters loose depth. When compacted,'will be compressed Road development sometimes
to about 15 centimeters thick.
adopted the stage construction methods which means, step by step improvement of the roadway, depending upon the availability of funds and dernand of increased traffic. The sequence of improvement could be as follows:
First: It might be an earth road surface. Second: Untreated gravel road. Third: Application of asphalt over the gravel.
Fourth: The use of stone type pavement with gravel as part of the base cotuse. Maintenance of gravel road surface is a routine activity spe-
cially in maintaining the smoothness of the surface under the following procedures:
l. 2.
J.
By cutting off a thin layer of the road surface using road grader distributing the scraped layer uniformly over the roadway surface. The cut is deep enough to remove the comrgations ofthe road surface. The blading sequence is once or twice a year or sometimes monthly, depending upon the finances, traffic and equipment availability. After blading, the road is compacted by road roller to maintain the cross section slope and th: crown of the roadway. The most effective routine maintenance is done immediately after rainfall where the surface is soft for the blade to drag. Losses of materials caused by grading and traffic wear generally ranges from Yr" to 1 inch of the thickness per year allhough it varies due to traffic volume, rainfall, wind intensity, frequency and maintenance practice or habit.
226
7-5 DPWH Standard Specifications on Aggregate Sub-Base Course The Department of Public Works and Highways classified the aggregate sub-base course as Item 200 which consists of furnishing, placing and compacting aggregate sub-base course on a prepared sub-grade.
Item - 200 Material Requirements That, aggregates for sub-base shall consist ofhard, durable particles of fragments or crushed stone, crushed slag or crushed or natural gravel and filler or natural crushed sand or other firrnly divided mineral matter. The composite material should be free of vegetable matter' and lumps or balls of clay that could be compacted readily to form a firm stable base. TABLE 7-2 GRADING REQTTREMENTS FOR ITEM 200
Conditions
l.
The fraction ing the 0.75 mm (200) sieve should not be greater than 0.666 (213) of the fraction ing the 0.425 mm No. 40 sieve. 227
Elements of Roads and Highwa5,s
2.
Constructing the Roadbed
The fraction ing the 0.425 mm (No. 40) sieve should have a liquid limit not greater than 35 and Plastic Index not more than 12 as determined by AASHTO T-89 and T90 respectively.
3.
Req
u
irements
l. 2. 3.
TABLE 7-3 GRADTNG REQUIREMENTS FOR rTEM-201 Sieve
Mass Percent
Standard Altemate US Standard 50
2u
38
1-l12
z>
1u
20
3/4" 7/2'
12
4;t5 0.425 0.075
No.4 No.40 No.200
The materials ing the 20 mm (3/4") sieve shall have a soaked CBR value of not less than 80%.
Item- 202 Material Requirements
The coarse portion retained on a 3.0 mm (N0. l0) sieve shall have a mass percent of wear not to exceed 50 by the Los Angeles Abrasion Tests as determined by AASHTO T-193. The CBR value should be obtained at a mum dry densit) as determined by AASHTO T-180 Method D
Tfeml[Ot lfaterial
4.
Grading B
4.
The portion ing the 0.075 mm (No. 200) sieve shall not be greater than 0.66 (Zl3) of the portion ing the 0.425 mm (No. 40) sieve. The portion ing the A.425 mm (No. 40) sieve shall have a liquid limit n(lt more than 25 and Plastic lndex not more than 6.
The coarse aggregate retained on 2.0 mm (No.lO) sieve shall have a mass percent of wear not more than 45 by L.A. abrasion tests, and not less than 50 rnass percent shall have at least one fractured face.
The material ing the 20 mm (3/4") sieve shall have a minimrrm soaked CBR value of 80%.
TABLE 7- 4 ITUNI 2(T CRUSTfID AGGREGATE BASE COURSES 60-85 oo-as 35-65
20-50
30-35
Mass Percent
Standard Altemate US Standard mm lnch
8-25
38
o-12
2-t4
25
I'
20
3/4*
t2
712',
4.'t5 0.425
No.4 No.40 No.200
0.075
That the fraction ing the 0.075 mm (No. 200) sieve shall have a mass percent of wear not to exceed 50. The fraction ir4l the 0.425 mm (No. 40) sieve shall have a liquid limit not greater than 25 and Plastic Index not greater than 6. The coarse portion retained on a 2.0 mm (No. 40) sieve shall have a mass percent of wear not to exceed 50. 228
B
t-t/2'
s-20
Conditions
Grading
100
60-85 60-90 30-35 8-25
35-65
2-14
5-1 5
l0-30
Item* 203 Lime Stabilized Road Mix Base Course This item consists of foundation for a surface course comof soil aggregate, lime and water proportion mixed on site and constructed on a prepared sub-grade or sub-base. posed
'229
Constructing the Roadbed
Elements of Roads and Highways
4.
Material Requirements
1.
Soil aggregates refers to the combination of gravel, sand, silt and clay, or other approved cornbination of materials free of vegetable or other objectionable matter that might be encountered in the construction site or obtained from other approved sources.
2. 3
The intent of the specification is to utilize soil existing on the roadbed if the quality is satisfactory according to the specifications and minimizing cost. On the contrary, if the material quality is poor or deficient, aggregate must be obtained wholly or partially from
"
5.
The equipment to be used includes: scariSer, pulverizer, mixer, spreader, hauler, water truck, compactor and finishing machine, including slurry line distributor equipment.
Distributor equipment should include: pressure gauge, volume measuring devices or a calibrated tank. It should "be equipped with power unit for ttre pump and full circulation spray bars adjustable laterally and vertically and also agitator to prevent settrng of solid lime.
Preparation of the Soil Aggregate
an approved outside sources.
Case
TABLE 7-5 GRADING REOTIREMENTS FOR ITEM.2O3
l.
Standard Alternate US Standard mnl
Inch
Mass Percent Pas Gradrng
100
2"
4.75
No.4
55-100
2.ffi
No. l0
45-100
0.425
No.40 No.200
25-80
0.075
I l-35
The existing roadbed is scarified lightly and bladed to a uniform grade according to the plan, then rolled, watered and rolled.
2. All depressions appearing on the surface are filled, and
B
50
- I For New Soil Aggregate
the weak portion of the roadbed is strengthened with new
3.
soil aggregate.
Allow one day for measuring, sampling and testing of the sample for approval of the qualrty and gradation before spreading the windrow for application of the hydrated lime.
4. If soil aggregate moisture
exceeds two mass percent of aeration by harrowing the soil aggregate until the moisture content is reduced to 2o/o or
th" dry aggregate, apply Conditions:
l. 2. 3.
5. That, the Plastic Index of Item 203 should not be less than 4 or more thar 10. The aggregate mass percent of wear should not exceed 50. Hydrated lime must conform to the requirements of Item 701- Construction Lime. The amount of lime added to soil aggregate should be from 2to 12 mass percent of the dry soil. Lime should not be applied during windy, rainy or with
less.
Finally, spread the aggregate smoothly and uniformly over half the road or other convenient width of the surface ready for the application of hydrated lime.
Case
l.
- 2 Salvage
Soil Aggregate
When materials in the site are to be used for mixing, the surface should be scarified lightly and bladed to a uniform grade conforming to the cross section of the plan.
impending bad weather. .:1J I
230
Blements of Roads and Highways
2. 3.
Constructing the Roadbed
The reshaped surface is scarified again to depth required leaving a foundation of undisturbed material parallel rvith the profile and cross section. The loosened materials are bladed into a windrow at the srde of the roadway. The undisturbed materia-ls are then rolled, watered and rolled.
then mixed by blading the mixture from side to side of the road, or by manipulation producing equivalent results until the whole rnass has uniform color. The mixture should be free from lean spots or balls of unmixed parti-
2.
Application of Lime
3. Application of lime shall follow correct procedures enumeratod as follows:
l. 2. 3. 4 5. 6. 7.
The hydrated lime is uniformly spreaded at specified percent using either the dry or slurry (wet) methods. The hme is distributed in successive applications at the arnount and intervals as prescribed. The rnixing equiprnent follows immediateiy behind the distributor after each application to partially mix the lime n'lth the soil aggregate. lt is applied only to specific areas as can be mixed into the soil aggregate during the day of application. Dry upplication is either by spotting bags of lime in equal pre-determined transverse and longitudinal intervals or by applying in bulk lime from equipped self-loading trucks. If lfune slurry (wet) is employed, the typical slurry ratio is 1,000 kilograms lime to 2 cubic meters water. The achtal mixing proportion depends upon the percent of lime specified, the tlpe of soil and its moisture condition. To prevent run-off and consequent non-uniformity of lime distribution, the slurry is mixed imrnediately after each spreading .
Mixing
4.
:3?
After the last lime application and partial mixing, the entire rnass of rnixture is withdrawn on the road surface and
Should the mixture show an excess of deficiency or uneven distribution of lime, the condition must be corrected by adding soil aggregate or lime then remixed. tf the mixture contains excessive amount of water or volatile matter, as may be encountered in slurry operation, it should be bladed, aerated or manipulated until the moisture and volatile content becomes satisfactory. Whether mi*ing is completed or not, all loosened materials are bladed into a windrow at the end of each day work and retained as such until operations resumed.
Spreading Compacting and Finishing The methods of spreading, compacting and finishing are enumerated as follows.
l.
The materials are spreaded by self-propelled pneumatic tired blade grader or mechanical spreader of approved type. Cutting into the underlying course should be avoided.
2.
After spreading, the surface is leveled to the road centerline, then to the outer edges of the road overlapping the shoulder.
3.
Each should terminate at least 90 centimeters in advance or to the rear ofthe end ofthe preceding .
4.
During the time of compaction, the surface is dragged or bladed as necessary to fill and remove incipient corrugation or other surface irregularities.
5.
Rolling must continue until after the surface is in uniform texture satisfactorily compacted.
lvlixing procedures are enumerated as follows:
L
cles.
233
Elements of Roads and Highways
6.
Constructing the Roadbed
Rolling should be stopped whenever there is an excessive pulverizing of the aggregate or displacement of the mixture.
Protection, Curing and Maintenance
After stabilizing the base course by lime,
it is protected
against rapid drying for a period of at least 5 days by either of the following curing methods:
l. A thorough and continuous 2. 3.
moist condition should be
maintained by sprinkling water. The surface must be covered with 50 mm layer of earth or sand and maintained in moist condition. The surface is applied wittr asphalt mernbrane of the type and quantity approved bythe Highway agency.
Item 204 Portland Cement Stabilized Road Mix
Mixture Proportion. The amounl of asphalt material to be added to the aggregate should be from 4 to 7 mass percent ofthe dry aggregate.
Item 206 Portland Cement Treated Plant Mix Base Course
A) Travel Plant Mixing Method: The salvage or new aggregate is pulverized until at least 80 mass percent of all the materials other than stone or gravel es a 4.75 mm (No. 4) sieve. Any material retained on a 50 mm (2") sieve and other unsuitable materials are removed.
Procedure:
l. 2.
Base Course This item consist of a foundation for surface course composed of soil aggregate, Portland cement and water, proper proportions of road-mixed placed on a prepared sub-grade or subbase.
Proportioning Mixture
l. 2.
The amount of cement added to the aggregate shall be 6
to
ofthe dry aggregate. Construction requirement and procedures is the same as that of Item-203 wherein the world lime is deieted and replaced with Portland cement. 10 mass percent
Item 205 Asphalt Stabilized Road Mixed Base Course Materials. Asphalt materials should be Anionic or Cationic Emulsion asphalt of the slow setting type. 234
3. 4.
Aggregates to be treated, is placed in uniform windrow spreaded to a uniform thickness to the required depth. Portland cement of proper quantity is applied uniformly in a trench on top of the windrows or spreaded uniformly over the aggregates.
Mixing is done by rnachine for thorough and uniform blended mixture. When this method is used, a maximum time of 2 hours is allowed for wet mixing, letdown and finishing.
B) Central Plant Mixing Method. The plant is equipped with feeding and metering devices that will introduce the cement aggregate and water into the mixer in quantities specified. Mixrng continue until after a uniform mixture is attained.
C)
Spreading, Compacting and Finishing. Not more than 60 minutes should elapse from the start of mixrng to compaction of the laid mixture. After spreading, the mixture is compacted and finished in accordance with the procedures as enumerated for lime stabilized road mix base course ltern 2'3.
7-6 Clearing and Grubbing 235
Elements of Roads and l{ighw*ys Clearing and Grubbing is categorized uneler ltem-100 of the
DPWH standard specifications. It consists of clearing, grubbing, removrrg and disposing of all vegetable matter and debris except those objects that are designated to remain in place or are to be removed in consonance with other provisions of the specifications. It also includes preservation from injury or defacement of all objects designated to remain.
Specifications for Clearing and Grubbing provides that:
1. All surface objects and all trees, stumps, roots and other protruding obstructions, not designated to remain should be cleared and/or grubbed including the mowing required as follows:
a)
Removal of undisturbed stumps and roots and non-perishable solid objects with a minimum depth of 90 centimeters below sub-grade or slope of embankrnents will not be required. b) Outside the grading limits of cut and embankment areas, stumps and non perishable solid objects should be cut off not more than 15 cm" above the ground line or below low water level. c) In areas to be rounded at the top of cut slope, stumps should be cut off flush with or below the surface ofthe final 5lope line. d) Grubbing of pits, channel changes and ditches will be required only to the depth necessary by the proposed excavation with such areas. e) Buming should be under constant care of competent watchman that the surrounding vegetation, adjacent property, or anything designated to remain on the right of way will not be jeopardized. Methods of Measurement
l.
Area Basis
-
by hectare and fractions thereof acceptably cleared and prubbed.
Constructing the Roadbed
2.
Lump Sum Basis. No measurement of area will be made for this item. 3. Individual Unit Basis (selective clearing). The diameter of trees will be measured at a height of 1.4 meters above the ground. Trees less than 15 cm. diameter will not be measured for payment. The unit basis will be designated and measured in accordance with the following schedule of sizes: Diameter at heigtrt 1.4 meters Over 15 cm. to 90 cm Over 90 cm.
- Pay item designated. - Small
-Large
7-7 Excavati0n Excavation is the process of loosening and removing earth or rock from its original position in a cut and transporting it to a fill or to waste deposit. Roadway excavation is classified into:
L 2. 3. 4. 5.
Unclassified excavation Rock excavation Common excavation Muck excavation
Borrowexcavation
UnclassiJied Excavation is the excavation and disposal of all materials regardless of its nature, or not classified and rncluded in the Bill of Quantities under other pay iterns.
Rock Excavation consists of igneous, sedimentary
and
metamorphic rocks that cannot be excavated without blasting or the use ofrippers and all boulders or other dstached stones each having a volume of I cubic meter.
Common Excavations are those that are not included in the Bill of Quotations under rock excavation or other pay items. Muck Excavations consist of the removal and disoosal of
I
236
237
Constructing the Roadbed
Elements of Roads and HighwaYs
l. Embankment Sub grade Shoulders
deposits of saturated or unsaturated mixtures of soils and organic matter not suitable for foundation matenals regardless of
2. 3.
moisture contents.
Borrow Excavation is the excavation and utilization of approved materials for the construction of embankment or for other portions of the work obtained from approved sources in accordance with the following requirements:
l.
Borrow Case -I: Materials obtained from sources designated on the plans or in the special provisions.
2.
Borrow Case
- 2:
Materials obtained from sources pro-
vided by the contractor.
Construction Requirements
l. '
When there is evidence of discrepancies between the actual elevations and that shown on the plans, a preconstruction survey with reference to the datum plane used in the approved plan is undertaken by the contractor or agency to serve as basis for the computation of the actual volume excavated.
2. All excavations
should be finished to smooth and uniform surface. As much as possible, no materials shall be turned to waste. Materials outside the limits of slope should not be disturbed by the excavation operations. Excavations should be done only after the clearing and grubbing in the
3.
area.
Top soil encountered in excavation and on areas where embankment is to be placed should be removed to the depth as the Engineer may determine and should be transported and deposited in storage pile designated area separated from other excavated materials for later use.
4. Slope 5. Bedding 6. Backfillforstructures
All
unsuitable materials that could not be properly compacted in embankment must be disposed of without delay for it might be included in the work when the engineer turn his back for a cup of coffee. Borrow materials should not be placed until after the fill accessible roadway excavation has been placed in the
fill.
Pre-Watering and Pre-splitting Excavation areas and borrow pits may be pre-watered before excavation. When pre-watering is adopted, the areas to be excavated shall be moistened to the frrll depth from the surface to the bottom of the excavation. The water must be controlled so that excavated materials will contain the acceptable moisture content to permit compaction to the desired density. Pre-watering has to be supplemented where necessary by truck watering unit to insure ttrat the enrbankmert materials contains the proper moisture at the time of compaction.
Pre-Splitting is drilling and blasting procedure that may be employed to control over break and to give a uniform face to the back slope or rock cuts. Pre-Splitting is performed by:
l. 2.
Drilling holes at uniform intervals along the slope line. Loading and stemming the holes with appropriate explo-
. sives and stemming materials.
3.
Detonating the holes simultaneously.
If the pre-splitting is under contract, prior to drilling operations, the contractor shall:
The Use of Excavated Materials
All
suitable materials removed from the excavation area are used in the formation of:
238
l.
Furnish the engineer a plan outlining ttre position of all explosive to be
drill holes, depth of drilling type and
used, loading pattern and sequence of firing.
239
Elements of Roads and Highways
2. 3. 4. 5.
6.
7. 8.
The drilling and blasting plan is for record purposes only, and will not absolve the contractor of his responsibility for using proper drilling and blasting procedures. Controlled blasting must begin with a short test section of length to be approved by the engineer. The test section shall be pre-splitted production drilled and blasted. Sufficient materials sample to be taken for ttre engineer to determine if the contractor's method is satisfactory.
The holes are charged with explosives of the size, kind, strength, and spacing suitable for the formation being presplitted, and with stemming material which es a 3 inches standard sieve which has the qualities for proper confinement of the explosives. The finished pre-split slope should be reasonably uniform and free of loose rocks. Variance from the true plane of the excavated back-slope should not exceed 30 centimeters. Localized irregularities or surface variations that do not constitute safety hazard or impairment to drainage courses or facilities will be permiued. The maximum offset of 60 centimeters will be permitted for construction working bench at the bottom of each lift for use in drilling the next lower pre-splitting pattem. The engineer may order discontinuance of ttre presplitting when the materials encountered are unsuitable for pre-splitting
7-8 Free Haul
-
Overhaul (Item 107)
Free haul distance is the specified distance wherein an excavated material will be hauled without additional cost. The free haul distance is 600 meters unless otherwise specified in the contract. The overhaul is an authorized hauling in excess of the free haul distance. For example, if the hauling distance of materials is 800 meters, considering that the free haul is 600 meters, t}ren the excess 200 meters is considered the overhaul. 240
Constructing the Roadbed
Methods of Measurement The overhaul distance for material obtained and placed within the rnadway limits will be measured along the centerline of the roadway. No allowance will be made for transverse of lateral movement to or from the c.enterline except materials moved to or from designated areas outside the roadway limits.
If the contractor chooses to haul materials frorn other route which is longer than the designated source, pa)ment will be based on the overhaul distance measured along the route designaled by the engineer. Payment will be made based on the number of cubic meters overhaul materials multiplied by the overhaul distance in kilometers.
7-9 Construction of Fills and Embankment An stable embarkment is atfained by spreading the materials into a thin layer then compacted at a moisture content closer to optimum. These layered process of compaction produces unifo.*rty and higher density of the material and moisture corrtent. On the other hand, filhng materials which are just durnped in thick layers even if compacted will have a varyrng density and moisture contents from one spot to another. This will result to differential settlement or swell between the adjacent areas of the embankment.
The AASHTO-ARBA t Commiuee on Compaclion of Earthwork proposed the following amendment to the original AASFIIO density requirements to wit:
1.
2. 3.
Granular aggregates or those with only slight degree of plasticity, should be compactedto 95%-100% Fine grained aggregate possessing a low degree of plasticity is compacted to approximately 100% at a moisture content near laboratory optimum. Densities for asgregate possessing moderate to high plasticity should not be so high as to lead to subsequent srvel241
Elements of Roads and Highways
Constructing the Roadbed
ling. Compacting procedures should not exceed the as_ gregate shear strength
4.
Clay soil should not be over. compacted beyond about 90Yo
to avoid post construction swelling.
The problems encountered in the control of embanlanent
construction are:
I.
Embankment Control Basically, there are two procedures employed
to
assure
w-ater.
specifi ed embankment density.
L
To specify the expected value to the minimum acceptable amount of relative compaction and to ascertain from the
fill density tests that the specified value is obtained. To specify tJre manner and methods of constructing the embankment particularly the layer thickness, moisture control and the number of es by a roller of specified
2.
type and weight.
2.
J.
a) c)
TABLE 7-6 RECOMMENDED MINTMUM REQUTREMENTS
of Soils AASHTO M-I45 A-1, A-3 A-2-4, A-2-5 A-2-6, A-2-7
A-4, A-5, A-6, A-7 Source: AASHTO M-57-64
r
** +
Compaction at 95% of T-99 optimum content. Usc of these materials rcquircs spccial design and construction. AASHTO Desig. M-146 basement soil compacted doil.
Density test requirements
b) Moisture control
1. Mrnimum Relative Density Requirements* +
c) Evaporation or rainfall during compaction. Some soil may not easily assimilate watei unless wefiing agent is employed, Sometimes soil type cannot be segre_ gated dunng construction unless brought to laboratory. Materials re hauled from different sources and segrega_ tion of the same type is difficult in the actual work.
Construction Requirements and Equipment
Field control is a matter of ascertaining and defining the specific procedures to be done. what is important is the manner and methods that will yield the expected result.
Class
Difliculties in maintaining uniform moisture content. This is due to: a) Variable wetness of the soil. b) Problems in evenly distributing and mixing in
2.
Compaction equipment like:
Tamping Roller varies from light unit test weight 6,000 to 10,000 lbs. for an 8ft width. For giant fully loaded roller, 75,000lbs for a l0 ft. width. Grid Rollers is effective in breaking down clods and soft
rock. 3. gPneumatic Tire Roller with rubber tires, weighing g tons or more. 200 tons for airport. Smooth Tired Roller of two or three-wheeled type used to compact bases and bituminous surface.
4.
5. 6.
Wbratory Compactor is effective in compactrng stones of
Macadam road. Hauling and Spreading equipment.
Embankment on Swampy Areas Conventional construction of roadways in swampy area is
242
243
Elements of R.oads and flighways
Constructing the Roadbed
not advisable because record shows that muck turd plate provide unstable for fills causing failure of highways and railroads. Construction of roadway through swampy area requires either of the following methods:
the muck speeding up :onsolidation. care should be exercised not to exceed the shearing strength of the muck otherwise, displacement of the muck and settlernent of the fill may take place. After a period of consolidation, the surcharge material is ,emoved and rq:laced with base course and temporary pavement.
l" 2.
Removal and replacement of unsuitable materials. Displacement under the followrng methods:
a) Surcharging method b) Vertical sand drain c) Fabric reinforcement
Affit
reduetion
Removal and Replacement Method is applicable where the unstable material is shallow or thin. Unstable materials are removed to the level of the underlying materials before fillmg.
Displacement Method. Imported materials are carefully placed along the advancing slope allowed to flow under the dense muck to displace it. Sometrmes a trench almost equal to the width of the embankment may 6e blasted out and backfilled at once with stable materials. The blast pushes part of the muck out of the trench and the other portion is liquified for easy displacement. Where muck is deeper or thick, the under-fill method of displacement is applied. The trench is bladted and a large volume of the fillmaterial is dropped to settle into the peak.
The Vertical Sand Drain Method provides rapid consolidation of deep layer muck. sand drains are vertical columns of sand that penetrate the muck almost to solid materials. Across this top is a horizontal blanket extending through the side slope of the fill. u'der the pressure induced by fill and surcharg", .ob surface water flows up the clrain and out of the fill. Rapid consolidation of the muck follor,i's.
The Fabric Reinforcement Method is covering the muck with permeable fabrics. Weight Reduction Method is installing a block of styro-
foam over the muck to reduce the weight of the fill.
DPWH Specifications on Embankment (Item-104) Embankrnent shall be constructed fined as:
acceptable that could be compacted in accordance with the contract as specified. Selected Borrow for topping. Soils graded particles that es a 75 mm (3") sieve square openings and not more than 15 mass percent will the 0.075 mm (No. 200) sieve. The material shall have a Plastic lndex not more than 6 and liquid limit not more than 30.
The Relief Method is also employed after the fill materials are dumped in place. Relief ditches are blasted along the side of the fill to displace the underlying muck.
244
de-
l. Suitoble Materials are materials
,,,,:
Surcharging Method is applied on low fill over shallow muck up to 30 or 40 centimeters depth. Where top of the muck is soft, displacement through careful filling is done. The fill is then built-up in compacted layers to its elevation allowing settlement to its final grade. Surcharge of un-compacted fill material is laid to add weight and accelerate the flow of water from
of suitable materials
2.
Unstabile Materials are materials other than suitable ma-
terials such as:
a)
Materials containing detrimental quantities of organic substances like grass, roots and sewage. 245
Constructing the Roadbed
Elements of Roads and Highways
b) c) d) e)
Highly organic soils like peat and muck. Soils with liquid limit exceeding 80 and or plastic index exceeding 55. Soils with natural water content exceeding I00yo Soils with very low natural density of 800 kg./^t or lower.
Methods of Construction
l.
Z.
Where embankment lower than 120 centimeters below the sub-grade is to be made, all s,rds and vegetable matters are removed from the surface" The cleared surface should be totally broken-up by plowing, scariffing or steeprng to a minimum depth of 15 centimeters. Sods not required for removal should be disc harrowed or scarified
4.
compaction.
Compaction The contractor shall carry out full-scale compaction trials on l0 meters wide and 50 meters long. Compac-
areas not less than
tion trials with the main types of fill materials to e used in the work should be completed before any work with the corresponding rnaterials is allowed to start. Throughout the period of compaction, the contractor should adherg to the compaction procedures found during the compac-
tion trials for each type of materials, comp4ction equiprnent employed, and each degree of compaction specified.
Roadway embankment on earth materials are placed in horizontal layers not exceeding 20 centimeters loose volume than compacted as specified before the next layer is
Protection of Roadbed During Construction.
When excavated materials contains more than 25 mass percent of rock larger than 15 centimeters in greatest diameter and cannot be placed in layers of the thickness prescribed without crushing, pulverizing or further breaking down into pieces, such materials may be placed on the embankment in layers not exceeding in thickness the approximate average size ofthe larger rocks bul not greater than 60 centimeters.
Lifts of materials containing more than 25 mass percent of rock larger than 15 centimeters in greatest dimension should not be constructed above an elevation of 30 centimsters below the finished sub-grade. The balance of embankrnent should be composed of suitable matenal placed in layers not exceeding 20 centimeters in loose thickness and compacted as specified for embankment.
246
Hauling and leveling equipment should be routed and distributed over each layer of the fill to make use of compaction efforts affording and to minirnize rutting and uneven
befbre thc construction of embankment.
placed.
3.
5.
During the construction of roadway, the roadbed should be rvell maintained and drained at all times. slide ditches or gutters emptying from cuts to embankrnent or otherwise should be constructed to avoid damages to embankment by erosion.
Rounding and Warping Slope Rounding. Except solid rocks, the top and bottom of all slopes including the slopes of drainage, ditches, are rounded as planned. A layer ofearth overlapping rock is rounded above as was done in earth slope.
Warping. Adjusfinent in slopes are made to avoid injury to of weather head rock or to harmonize with, existing landscape features adjusting to thd gradual slope. At the intersections of cuts and fills, slope are adjusted and warped to flow into each other or into the nafural ground surface without noticeable break. standurg trees or marring
),47
Elements of Roads and Highways
Constructing the Roadbed
7-10 Sub-Grade Preparation
vertical structures, roads or other structures it is important to know if the in place materials possesses the following proper-
Sub-grade preparation is categorized under ltem 105 ofthe DPW standard specifications. The sub-grade is prepared for the
ties:
1. 2.
of overlying structural layers extended to the full width of the roadway.
3.
Material Requirements
l. 2.
4. 5.
Except when the sub-grade is in rock cut, all materials below the sub-grade is leveled to a depth of 15 centimeters or more as specified to meet the requirernents of selected borrow toppings Prior to start of the sub-grade preparation, all culverts cross drains, conduits and the like including the backfill, ditches. drains and drainage outlets are thoroughly com-
These desirable features could be achieved with compacted
Highly desirable characteristics such as strengtlr, low compressibility and stability is associated with high densrty values as a result of using good materials and proper compactron.
Any type of soil may be used for structural fill provided that it does not contain organic or foreign materials that will decompose or otherwise undergo changes after it is placed.
Sub-Grade Level Tolerance The finished compacted surface ofthe sub-grade shall conform to the allowable tolerance specified as follows:
l.
Permitted variance from design
+20mm -30mm
3" Permitted surface irregularities
4. 5.
measursd by 3 meters straight edge Permitted variance from design cross-fall of camber Permitted variance from design longitudinal grade over 25 m. long
,
The water content in the soil fill has substantial effect on its stabilrty and rn the process of compaction. Fine grain silt, and clay soil, or granular soil containing fine materials are affected by vibrations due to its water contelrt. Soil that is too dry is difficult to compact and those that are too wet are difficult to spread and compacted.
+ 30mm
Generally, compacted silt is stable. It is capable of developing fairly good strength and has litfle tendency for volume change. But silt soil is difficult to compact if wet or if work is
0.5%
performed on rainy period.
+ O.lyo
7-11 Compaction and Stabilization Whether the soil is used as foundation material to a40 Ln0
The soil must be durable and save against deterioration. The soil must possess proper permeability.
fill of selected types of soil properly placed and arranged.
pacted. Any work on the preparation of the sub-grade should not be allowed to start unless approved by the supervising engineer.
2. Levelof service
That, the soil must have adequate strength. The soil must be relatively incompressible to avoid insignifi cant funrre settlement. The soil must be stable against volume change as water content or other factors varv.
Compacted clay has very low permeability, an advantage where movement of water needs to be restricted, but clay soils cannot be compacted properiy when wst. If the height of the fill is reasonably high, marginal materials to be placed under water
should consist
of
coarsc granular materials. Fine grain soil
should be avoided.
249
Elements of Roads and Highways
Constructing the Roadbed
The thic}ness of the initial fill should be greater than the normal fill in order to create a working pad capable of ing equipment used for the subsequent placement and compaction of the fill.
particles tend
Equipment for Compaction
rangement.
l.
2. 3.
4.
The Pneumatic or nrbber tired rollers.
The drum type roller with projecting feet or logs called the sheep's foot roller. Vibratory compaciors. Smooth
This natural frequency refers to the value at which the soil to oscillate in unison giving maximum effect to the repeated impact imposed by the compactor instead of having a random oscillation of particles that would create damping effect. Thus, shaking the particles into a more compacted arThe Smooth Drum Roller has limited depth of compaction' This is not suited for compacting earthfill due to the size of the drum and the large soil . This $pe can be utilized for compacing limited thickness such as granular base course on highways and the like.
'Ihe hteumatic Tire Roller can be used effectively on all types of soils. It compacts by kneading available as selfpropelled unit or as towed units. Load sizes vary from 20 tons to 200 tons of which, 50 tons is commonly used.
The smooth drum roller can be used on earth moving projects to seal the surface of the fill at the end of each workday providing smooth surface for the water to rapidly run-off fiom the work area.
Light rollers of 20 tons type can compact 6 inches thick layer with few es. The 40 to 50 tons roller can compact 12 inches thick layer with 3 to 4 es. The heavy 200 tons type was proven to compact layers up to 18 inches thick with limited number of es.
Compaction Equipment and Density Control Strips
Tlre Sheep's Foot Roller is limited to cohesive soils. Its pressure varies from 700 lN/m'?
6
4,200ld\f/m'?.
The Vibratory Compadar is the most effective compactor on non-cohesive soils available as:
1.
2. 3.
Vibrating drumtype. Vibrating pnzumatic tire. Vibratfug plate equipment.
On some vibratory compactors, the vibrating frequency can be varied by operation. The frequency riurges between 1500 and 2,500 cycles per minute that is within the natural frequencies of most soil. 250
Compaction equipment should be capable of obtaining compaction requirements without detrimentally affecting the compacted materials. The compacting unit may be of any type, provided that they are capable of compacting each lift of material as specified and meet the minimum requirements.
Minimum Requirements for Road Roller
l. 2. 3.
Pneumatic Tire Roller must have smooth thread tires of equal size that will provide uniform compacting pressure for the full width of the roller and capable of exerting ground pressure ofat least 550 kN ( psi). Sheepfoot Tamping as grid roller should be capable of exerting a force of 45 Newton per millimeter (250 psi) of length of roller. Vibratory Steel Wheel Roller must have a minimum mass of 6 tons. The compactor is equipped with amplitude and frequencY controls. 251
Elements of Roads and llighways
4.
Steel Wheel Roller. Other than vibrato{, should be capable of exerting a force not less than 45 Newton per milli meter of width of the compression roll or rolls.
CHAPTER
TABLE 7.7 SOIL COMPACTION CIHRACTERISTICS
CONCRETE PAVEMENT
AND RECOMMENDED COMPACTION EQTIIPMENT Gcneral Soil Description Sand
&
sand
Gravel mixturc (no silt or clay) Sand or SAnd
uninei soit
Compaction
Classification
Charactcristics
Sa, SP,
Gw
Good
8-1 Portland Cement
Equipmcnt
Vibratory down roller Vibratory rubbcr tire or pneumatic tire cquipment
Sm,GM
Good
Gravel with
Clay
silt
:ndcd Compaction
ML
Good !o Poor
Vibratory down roller Vibratory rubber tirc, Vibratory sheep's foot
Fair to Poor
fmt
CL
Good to Fair
Pncumatic tirc, shc's foot, vibr8tory sheep's foot and rubber tire.
CH Organic Soil
OI,OH,PT
Fair to Poor
The different types
-do-
Not recommended for strrrctural carthfill
Portland cement specified by
1.
Type 1 or 1A (Air entraining). This type of cement is for general concrete construction when the specified properties ofthe other four types are not required.
2.
Type II or IIA (Air entraining) This type is for general concrete construction exposed to moderate action or where moderate heat of hydration is required.
3.
Type
III
or IIIA (Air entraining) This type is for high
strength concrete.
4. Type IV is for low heat of hydration. 5. Type V for high sulfate resistance Generally, Portland cement constitute the following chemicals:
l.
2. 3. 4. 252
of
AASFITO are the following:
Pneumatic tire,
Vibratory rubber tirc Vibratory sheep's foot sheep foot typc
Clay
substances.
Pneumatic Tire Vibratory rubbcr tirc,
Vibratory she's MH
Portland cement is a combination of limestone, marl or other calcareous materials and clay, shale, or like argillaceous
Tricalcium Silicate (C3S) Dicalcium Silicate (C2S) TricalciumAluminate (C3A) Tetracalcium Alumina Ferrite (C4AF) 253
Elements of R.oads and Highways TABLE
AND STRENGTH CHARACTERISTICS OF VARIOUS TYPES OF PORTLAND CEMENT
Types ofCement
Comp. Strength Normal Portland Cement Concrete
Compor.rnd Percent
r7283 I
Concrete Pavement Design Assumes the Following Considerations:
8-I COMPOSITION
Cornpound
II
Concrete Pavement
- Normal - Modit'ied
III - High Early IV - Low Heat V - Sulfate Resistant
50 24 lt 4233 5 60139 26 50 5 40404
100
100
75
85
8
190
120
t2 9
55
r))
55
lJ
That, transverse cracks on the concrete pavement cannot be avoided. The designer however, presumes that pavement cracks could be controlled, by providing reinforcements to the slab ts with the following assumptions.
2,
day days days
8
beams.
Percent
C3S C2S C3A CAAF
l3
L That, the pavernent slab was designed as plain concrete
100
90
110
75 75
months 100 100 100
a) With reinforeemen! cracks on the slab will be
t00 100
b) 8-2 Concrete Pavement Characteristics and Behavior
c)
The behavior of concrete pavement that is exposed to loading and environmental effect entirely depends upon the quallty of concrete, the underlying sub grade, and the base course. Generally, concrete is strong in resisting compression load acting on it, but considerably weak in resisting tensile stresses. Thus, concrete pavement actrng as a berrm, resting on a weak sub-grade and base courses, is also weak in carrying heavy load associated with impact forces. The reaction and movement of the sub-grade ing the slab, affects the stability of the concrete pavement.
Concrete like other materials also expand and contract due to temperature changes. It expands when wet and contracts when dried. After pouring, concrete shrinks as the mortar hardens and the cement hydrates. Concrete pavement changes in
length with time of day for being exposed to different elements of weather changes. A curl tendency is very likely due to the effect of daily and seasonal temperature and moisture differences between the top and bottom of the slab. 254
'
conlined to a weakened plain ts spaced at 4.50 to 6.00 msters distance. Vertical offsetting across the narrow cracks will be prevented by aggregate interlock, or by dowel bars.
Wrth simply reinforced slab, cracks will only appear at weakened plane ts spaced at 12 ta 20 meters intervals. Hair cracks to be hetd tigldy by the steel between ts.
ts are omitted. Hair cracks are checked by the steel and developed at close intervals. Faulting is countered by aggregatn interlock and
d) With continuous reinforcemen! transverse
e)
steel bars.
That longitudinal cracks on the pavement slab more than one lane wide is inevitable.
4.
Pavement slab is ed by foun
Definition of Deterioration. Deterioration of concrete pavement is due to stress brought about by load, moisture and temperature.
255
Elements of Roads and Highways
Concrete Pavement
Distress of Concrete is generally grouped intcr the following categories: a) Distortion b) Cracking c) Disintegration
Distortion is a vertical displacement of concrete slab at the ts or cracks. Distortion is due to failure or weakness of concrete ts.
Faulting. For faulting to occur, there must be free water on top of the base corrse and pavement deflection across the t due to hearry axle loads. Faulting is the result of'pumping tremendous force or load that develop urder pavement. Causes
offaulting are:
a) Loss ofslab b) Erosion of sub base
Cracking can take many forms in concrete pavement that could be the result from; applied load, temperqture or moisture changes.
The most common type of cracks are:
a) b)
Corner craclcs associated with excessive corner deflection Transverse craclcs associated with mixture or temperature stresses, or poor construction methods.
Disintegration appears in the form of durability cracking, scaling or spalling, as the result of mix design or construction related problems like: a) Durability Crachng. Results from freeze-thaw action. b) Scaling. A network of shallow fine hairline cracks which extend through the upper surface ofthe concrete. This is
the result from deicing salts, improper
construction,
freeze-thaw cycle, or steel reinforcement too closed to the surface.
2\6
c)
Spalling is the breaking or chipping of the t edges. It is the result from excessive stresses at t, weak concrete, poorly designed or constructed ts
Changes in Temperature and Moisture Content create slab curling, flexure stresses and overall lengthening and shortening of the slabs. The tendency of the slab to ,shorten is due to temperature drop or drying that create tensile stresses" On the other hand, the tendency to lengthen is due to temperature rise or increased in moisture that creates compression stresses.
8-3 Control of Cracks Load transfer anci t alignment is sometimes dependent solely on aggregate interlockrng. If the t opening is considerably small from .03 to .04 inch, the projecting aggregate is considered tightly keyed, and w'hen the edge of one slab deflects due to load. the ading edge will also be forced down. the ts open so wide, the aggregate interlocked is considered ineffective as a means of load transfer. Although some ageniies employed designs based on aggregate interlocked, others adopted the use of steel dowels as load transfer devices at the pavement ts.
If the coarse aggregates are weak, as when
Dowels can be painted, greased or coated with asphalt for almost one half of their length to break the bond with concrete, allowing the dowels to slip within one of the abutting slab ends. Skewed fiansverse contraction t in plain concrete pavement is being adopted. ts are slanted 60 centimeters in each 3.60 meters lance from the normal position. The offset places the inside of a double tire of a truck just forward of the t and at the same time the outside wheels are just behind the t.
8-4 Transverse Expansion ts Expansron ts provide space allowance for the lengthen251
Elements of Roads and Highways
Concrete Pavement
ing of slab due to expansion. Because of the so many buckling upward of concrete pavement, Engineers have come up with a conclusion that these blowups serves as conclusive evidence that expansion t is necessary,
Since year 1940, the provision for expansion t at interval of 30 meters or less was almost universally practiced in load building. The reason for providing expansion t is to prevent blowups by relieving direct compressive stresses before reaching the stage of unmanageable level.
TABLE 8-2 RTCOMMENDED DTMENSTONS OF DOWELS FOR CONCRETE PAVEMENT TS Dowel Diameter
Dowel Length
Dowel Spacing
Thickness cm.
mm
meter
mgter
15.0
20
.45
.30
17.5
25 25
.45
.30
20.0
.45
.30
2.2.5
32
.45
.30
25.0
32
.45
.30
27.5
32
.45
.30
.45
.30
Pavement
30.0 Source
:
AASHTO lnterior Guide & Proposed Revision 1980 (c) Longitudinal t
(a) Contraction t
T-
Based on the shrdies of more than 5,000 blowup samples, it was found out that blowups occurred mostly in mid afternoon at a temperature above 90"F during a peiod preceded by varying amount of precipitatrons.
8'5 Longitudinal ts Longitudmal ts are provided between adjacent traffic lanes. It is considered as hinges to provide edge , but allows rotation between the slabs" By this t, flexural stresses that might cause irregular cracks along the length of the road are relieved or neutralized. Longitudinal ts cannot be considered as a major problem under the followrng assumpttons:
1. 2.
Thatthere is no big load transfer across it. That, the expansion and contraction movement developed across the pavement width is very small small.
T
J Sawed or forrmed groove
Load transfer if specified
Longltudhd Jcllt Deformed tie oar
Formed groove
;+1.-W
+ 114min
(b) Expansion t F|GURE
258
(d) Construction t
8-1 BASIC TYPE OF CONCRETE PAVEMENT TS
FIGIJRE 8.2 LONGITUDINALT LOAD TRANSFER 2-i9
Elements of Roads and Highways
3. 4. 5. 6.
Concrete Pavement
When lanes are constructed at different time using side forms, the ts are provided with key way in the first slab to accept load transfer. For longitudinal t, deformed tie bars are used because the purpose is to hold the slabs tightly together, rather to allow the ts to open and close. The diameter and spacing of tie bars are based on the force needed to pull the narrow pavement slab over the sub-grade to the jornt. The length of tie bar is determined from the ernbedment irrside the concrete necessary to develop the strength of the bar.
&
Working
Pavement
Stress
Thickness
Grade Steel Grade 40
expand and
fill the space completely.
8-7 Reinforcement of ts Steel reinforcement for ooncrete pavement ts are specified in the design to prevent the widening of cracks produeed by shrinkage or thermal contraction.
BARS FOR LONGITUDINAL TABLE E.3 RECOIVIM"*'O ''' 3.60I}I. LANE WIDTH TS IN CONCRETE PAVEMENT Type
ving and air blown asphalt sometimes mixed with mineral filler, rubber asphalt, and various rubber compounds. They are poured hot and stiff, then cooled, others are placed cold. There are some pre-formed sealant made of strips of extruded neoprene compressed for insertion into the groove ts, the sealant will
lD" Bar Diameter 5/8" Bar Diameter Length Maximum Lcngfh Maximum
psi
cm.
meter
30,000
l5
.60
1.20
Spacine m.
m. .75
S
1.20
Billet or
20
.60
1.00
.t)
r.20
Axle Steel
25
.60
.80
,75
1.20
The rernforcement holds the fractured faces in rigid preserving the aggregate interlock and the intrusion of dirt or water. These reinforcing bars however, is not intended to resist flexural stress being produced by loads or curling.
The reinforcing steel bars are mounted in one layer along the middepth of the slab. The formula used in deg this reinforcement for conirete slab t is:
As= Lfw 2S
8-6 Construction t If
will be interrupted for quite some time that cold joirat will be inevitable, the practice is to provide a transverse construction ts. Deformed tie bars are used to hold the t tightly closed together. However, if the construction t replaces a contraction t, the use of dowels is the concrete pouring
alternative. Construction ts and cracks should be cleaned and sealed prevent infiltration of rvater to the sub-grade and to keep dirt to out of the ts. Materials fbr such purpose includes harder pa260
where:
As= I_ L_ fr-
S_
Area ofstqel cross section per foot ofslab. Length of slab between ts in feet. Coefficient of friction between the slab and the sub-grade called the coefficient of sub-grade resistance ranging from I to 2 with 1.5 recommended by AASHTO Interim Guide. Working stress in the reinforcing steel in pounds per sq. in. AASHTO Interim Guide suggested working stress from 30,000 to 45,000 psi depending upon the type and grade of steel. 201
Concrete Pavement
Elements of Roads and Highways Weldpd wire fabrics are also used as reinforcement for concrete pavement made from cold drawn steel wires having the foll
gressive.
:
Minimum allowed tensile strensth Yield strength Reinforcing bars of billet, rail or axle steel yield strength among them from
80,000 psi 70,000
Pumping is minimal, where *,he sub grade had been constructed resistant to erosion by cement or bituminous treatnent, or when the pavement slab is underlain by proper$ graded granular materials.
40,000 to 75,000
8-8 The Sub-Grade and Sub-Base for Concrete
Pavement
.
The construction standard for sub-grade and embankment are precise and almost typical for ali pavement types. Under the concrete pa'vement literature, the under coulse of selected material is always irnposed upon between the sub-grade or embankment and the concrete slab. The AASHTO Interim Guides, recommend that the subbase must be extended from 30 to 60 centimeters outside the pavement cd,ge to serve as an edge . For +"he heaviest traveled facilities, a treated cement asphalt sub-base is recommended because it increases the fatisue life and reduces ioint failure.
lhe wide acceptance of stabilizing the sub-base with Portland cement concrete pavernent is due to the investigation result of pumping of concrete slab. Pumping is the ejection of water and sub-grade soil through ts and cracks along the edges of the concrete pavement. the A repeated depression ofpavementts by heavy axle load is tJre activating factor in pumping. With the presence of water on the sub-grade and churning it with the soil, activates the fluid forming slurry that expel to the surface. A continued punrping by heavy axle load will flush the soil frorn beneath the pavement to the effected locations. Failure of the t v,,ill be noticed followed by transverse cracking 2{i2
or breaking of comers. One crack will invite more chances for pumping action, t failures and by cracking that will be pro-
Despite the continued studies, researches and experimental development made, there is no assurance for an ffictive means of excludintg free water from the under pavement ts, craclcs and edges. So far, the use of under-courses with drainage provision is being considered as the solution to prevent pumping.
8-9 Concrete Proportions The fundamental rule to obtain good concrete is the proper selection of cemerfi aggregate and water thus:
l. Type I
or II cement is specified for concrste pavement. Water for concrete must be clean, free from acids, alkali and oil. Water that is suited for drinking purposes is acceptable for mixing cement except water containing large amount of sulfate. 3. [f concrete is to be strong, sound and durable, the aggregate must have similar properties. 4. The mineral aggregate of concrete is about 75%o of the volume or about 80% of the weight of normal pavement. 5. The maximum size of coarse aggregate is 2 inches. However, the use of larger aggregates according to some experienced highway engineers increases its length and durability. This precept is ed'by reasons that, with larger aggregate, less water is needed thereby, increasing the ratio of cement to water. Under the cement water ratio principle, concrete is stronger when water content is less.
2.
263
Elements of Roads and Highways
ixture Adrnixture is a substance added in mixing to change the characteristic of concrete mixture. There are varieties of ixtures available like, lhe air-entraining ixture, which is very comrnon. Others, like water reducer, retarder, accelerator, pozzolan and plasticizer are also used.
Air Entrainment Air entrainmsnt is the entrapment of air in the concrete mixture in the form of evenly distributed small bubbles It is used to increase the concrete resistance to surface scaling caused by deicing with calcium or sodium chloride. Another working advantage of air entrainment is improving its workability and reduces bleeding in fresh concrete.
The efrectiveness of air entrainmerrt is to increase the concrete durability that is influenced by:
l. 2. 3.
Percentage of air present in the mixture. Grading of aggregates. Size and distribution of air bubbles.
Air entrainmerf in concrete may the attained by using Air Entraining Portland Cement or by Air Entraining irture added to each batch of concrete while mixins.
Concrete Pavement
Durability therefore, is dependent on the water-cement ratio that should be properly controlled to obtain richness of the paste. AASHTO Guide Specifications for highway construction established the maxirnum water cement ratio at 6 gallons per bag of cement on normal conditions and 5 % gallons per bag of cement for severe atmospheric conditions.
8-10 Concrete Mixture Considering the high cost of cernent, the objectwe in mixing concrete is to use more aggregates and as lrttle cemenl as possible, while maintaining the workability necessary for a successful pouring and consolidation.
For structural concrete poured in inaccessible small areas around reinforcing bars, it is necessary to over-fill the voids or spaces around the aggregate and reinfbrcement using a foee flowing cement in water paste forrn. On tlrc conttary, pavement where the slab is open and thin with an access to manipulate from the surface, a drier mixture can be poured inside the form with ease and success. Thus, a higher percentage of aggregate and a less fluid cement-water paste can be used.
On how to reduce the amount of cement-water paste and the cost of the mixture u'e have to:
l.
Allow the larger size of aggregate that can be accorffno-
2.
dated in the pavement slab. Ascertain the aggregate is uniformly graded from coarse
Cement and Water Ratio As mentioned earlier, the strength and other desirable properties of concrete mixture varies depending upon the ratio of concrete to mixing water. A non air-entrained concrete with a water cement ratio by weight of 5 gallons of water per bag of cr:ment may have a compressive strength of about 5,300 psi in 28 days. On the other hand, a mixture of concrete with 7 gallons of water per bag of cement has developed strength of 3.700 psi only for 28days. 264
3. 4.
to fine.
Avail of the biggest quantrty of coarse aggregate consistent with proper workability. Adopt the lowest slump consistent with the proper pouring and finishing.
For concrete pavement, the specified value of slump is 1-2 or 2-3 inches. The slump test (AASHTO T-l l9) is the old tradi265
Elements of Roads and Highways
Concrete Pavement
tional and most widely used method in determining the consistency of concrete. A truncated cone of metal sheet 12 inches high with the base and top diameters 8 inches and 4 inches respectively is filled in 3 layers with fresh concrete. Each layer is rodded 25 times. Then the cone is lifted off vertically, allowing the concrete to subside. The slump is the height in inches that the top of the specimen falls.
is determined by the trial batch method, is obtained as final proportion for mixhrre desired the after until mixture. the succeeding Concrete mixture
8-11 Polymer Concrete Polymer Concrete could be used alone or in combination aggregates together producing
with Portland cement to bind concrete.
Polymer mirture is classified into thefollowing: 1.
2.
Polymer-Impregnated Concrete (PIC) is a portland cement concrete impregnated with monomer after curing Polymer Concrete (PC) is a rnixhre of polymer binder and aggregate.
a
Polymer Cement Concrete (PCC) is a pre-mixture of cement paste and aggregate wherein a monomer is mixed before curing.
20 cm.
Polymer possesses a higher strength concrete, but due to its prohibitive cos! its use is being limited to bridge deck or repair
of spalled ts. FIGURE
8.3 SLUMP TEST
Another way of testing the consistency of concrete is by the Kelly Ball method (see ASTM C-360). The apparatus is a metal cylinder 15 centirneters diameter and 12 centimeters high with hemisphere bottom shaped weighing 14 kilograms. A graduated handle rising from the top of ball es through a metal frame that is 30 cm. apart. The ball is placed on the surface of the fresh concrete. Its penetration is measured by comparing its position with that of the frame.
8-12 Curing of Concrete Pavement Newly placed concrste pavement needs curing. Curing may be accomplished by several methods but basically; all the methods could be categoized into two:
l.
Those that keep the surface constantly wet or cover it with water absorbent material that is re-wetted from time to
time. that pavement evaporated from the water already in the concrete which is retained is sufficient enough for hydration.
2. Those The advantage of Kelly Ball method is that reading could be taken immediately on the concrete being poured on the roadway. On the contrary, the slump test requires more time but could be conducted only on selected samples" 266
The chemical action between cement and water produces 267
Elements of Roads anC Highways
Concrete Pavernent
strength of concrete. If the concrete dries rut quickly, hydration and strength process will stop, but when moisture becomes available during hydration, strength gain will continue.
It
ties. 2.
Rapid dryrng of fresh concrete will result to surface crazing or cracking. Under extrerne hot weather or dry winds, severe cracking will eventually occur. The shortest period of curing for normal concrete is 5 days according to AASFITO recommendation.
Concrete pavemant is categorized under item 3l standard specifications, which provides that.
I
of DPWI{
Fine aggregates from different sources of supply should not be mixed or stored in the same pile nor used alternately.
3.
Fine aggregates should not contain more than 3 mass percent of materials ing the 0.075 mm (No. 200 sieve) by washing nor more than one mass percent each of clay lumps or shale.
4.
The use of beach sand will not be allowed without the approval of the supervising engineer.
5.
Ifthe fine
8-13 DPWH Specilicafions on Concrete Pavement
shall be free from injurious amounts of organic impuri-
aggregate is subjected to 5 cycles or the sodium sulfate soundness test, the weighed loss should not exceed 10 mass percent.
This item shall consist of Portland cement Concrete pavement with or wrthout reinforcement, constructed on the pre-
If fine aggregrte is subjected to test for organic impurities and a color darker than the standard is produced, it should be rejected. However, when tested for the effect of organic impurities of strength or mortar by AASHTO T-7I,
pared base in accordance with the plans and specifications.
Material Requirernents: Portland cement shall conform to the applicable requirements of Item 0-700, hydraulic cement. Only fpe I Portland cement should be used. Different brands or the sarne brands from different mills shall not be mixed nor shall they be used
the fine aggregate may be used if the relative strength at 7 and 28 days is not less than 95 mass percent. TABLE 8-4 GRADING REQUIREMENTS FOR FTNE AGGREGATES Sieve Designation
alternately unless approved by fhe supervisrng engineer. Cement that for any reasons become partially hardened, or which contains lumps or caked cement including those salvaged from discarded or used bags, should not be used.
10.0 mm 3/8"
mm 1.18 mm 0.30 mm 0.15 mm
4.75
Fine Aggregates:
1.
Fine aggregate shall consist ofnatural sand, stone screening or other inert materials with similar characteristics or combination thereof, having hard strong and durable particles.
Mass Percent 100
No.4
95-100
No. 16 No. 50 No. 100
45-80 5-30
0-10
Coarse Aggregate
1.
Coarse aggregate shall consist of crushed stone, gravel, blast furnace, slag, or other approved inert materials of
268 269
Concrete Pavement
Elements'of Roads and Highways Similar character or combinations thereof, having hard, 2.
J.
4.
strong durable pieces free fr.om any adherent coatings. Coarse aggregate should contain not more than one mass percent of material ing the 0.075 mm (No. 200) sieve nor more than 0.25 mass percent of clay lumps, not more than 3.5 mass percent of soft fragments. Ifthe coarse aggregate was subjected to 5 cycle ofthe sodium sulfate soundness test, the lost weight should not exceed 12 mass percent. It should have a mass percent of wear not exceeding 40 when tested by AASHTO T-96. If slag is used, its density should not be less than I 120 kg
Per cubic meter. The gradation of the coarse aggregate should conform to table 8-5. Only one grading specification should be used from anv one source. TABLE 8-5 GRADING REQUIREMENTS FOR
Reinforcing Steel The Specifications states that: dowels and tie bars to be used in concrete pavement shall conform to the requiremants of AASFIIO M-31 or M-42 except that rail steel shall not be used for tie bars to be bended and re-straightened during construction. Specifications further provides that:
l. 2. 3. 4.
COARSE AGGREGA1IE
Tie bars shall be deformed bars. Dowels shall be plain round bars delivered to the site with on€ half of each dowel length painted with one coat of approved lead or tar paint. The sleeves of dowels shall be metal of approved design to cover 50 mm plus or minus 5 mm of the dowels, with a closed end, with a suitable stop to hold the end of the sleeve at least 25 mm from the end of the dowel. Sleeve shall be of such design that they do not collapse during construction.
Mass Percent Sieve Designation
Grading
Grading
Grading
B
c
mm
lnch
A
75.0
3"
100
63.0
2-tt2
50.0
37.5 l-l/2"
25.0 20.0 12
4.75
90-100
2" 25-60
lu 3/4"
o-io
l/2* No.4
0-5
100
roo
90-100
90-100
35-70 0-15
35-70
0-5
ro-lo 0-5
t Fillers t fillers should be mixed asphalt and mineral or rubber filler. The pre-formed t fillers are punched to adrnit the dowels. Filler for each t should be furnished in a single place for the full depth and width of the t.
Storage of Cement and Aggregate The storage house for cement should be waterproof with raised floor from the ground to protect the cemerf from rain or dampness.
Water Water to be used in concrete mixing or curing or other designated applications should be clean and free from oil, salt, acid, alkali, grass or other substances injurious to be finished product. Drinking water if used needs to be tested. 270
L
The provisions for storage should be ample enough and the shipment of cement as received is separately stored in such a manner as to allow the earliest deliveries to be used first and to provide easy access for identification and inspection of each shipment. 271
Concrete Pavement
Blements of Roads and Highways
2.
Storage house must have the capacity to accommodate suffrcient quantity of cement to allow sampling at least 12
3.
To secure uniformity of concrete mixture, the coarse aggregates are separated into two or more sizes. Different sizes of aggregates are stored in separate bins or in sepa-
Quality Control of Concrete
rate stockpiles sufficiently remote from each other to prevent the materials at the edge on the piles from becoming
fi cations provides that
concrete pavements using a minimum of 75 rnm verrtional concrete as the surface course.
days before the cement is used.
For quality control of concrete in general, the DPWH speci-
trol of all materials during the handling, blending mixing and placement operations. The contractor shall furnish the engineer a Quality Control PIan detailing the production control procedures and the type and frequency of sampling and testing to insure that the con-
Proportioning, Consistency and Strength of Concrete Prepare a design mixture based on the absolute volume method as specified in the American Concrete Institute (ACI) standard "Recommended Practice for selecting Proportion for normal and heavyweight concrete". The intent of this specification is to require approximately 9.0 bags of cement per cubic meter of concrete based on a 40kg. Weight per bag of cement. However, leaner or richer mixhrre may be used in order to meet the minimum strength requirements.
2.
The engineer will determine from{he laboratory tests The materials to be used, the cement content and the proportions of aggregate and water that will produce a wdrkable concrete having a slump of between 40 and 70 mm (1112" to 3") if not vibrated, or between 10 to 40 mm if vibrated and flexural strength of not less than 3 8 Mpa (550 psi) when tested by the third-point method or 4.5 Mpa (650 psi) when tested by the mid-point method or a compressive strength of 24.1 Mpa (3,500 psi) when tested at fourteen days.
3.
The designer should consider the use of lean concrete (econo-concrete) mixture using local materials or specifically modified convsntional concrste mixture in base course and in the lower course of compoeite, monolithio
272
:
"The contractor shall be responsiblefor the quality con-
intermixed.
l.
of con-
crete produced complies with the specifcafions. The supervising Engineer shall be provided free access to recent plant production recards, and if requested infctrmutional copies of design, materials certifcations and sampling and resting reports."
Required Qualification of Workmen Concrete Butcher - The person performing the batching or mrxing operation capable of accurately conducting aggregate surface moisture determinations and establishing correct scale weight for concrete materials. Concrete Technician - The person responsible for concrete production control and sampling and testing for quality control proficient in concrete technology having a sound knowledge of the specifications as they relate to concrete production. He shall be:
L 2.
Capable of conducting test on eoncrete and concrete materials in accordance with the specifications. Capable of adjusting concrete mix designs for improving workability emd specification compliance and preparing
trial mix design. 273
Concrete Pavement
Elements of Roads and Highways
3.
He shall be qualified to act as the concrete batcher in the absence ofthe batcher.
8-14 Equipment The equipment and tools necessary for handhng materials and performing all phase of the work shall be approved by the supervising Engineer as to design, capaclty and mechanical conditron. The equipment should be at the job site sufficiently ahead of the start of construction operations to be examined thoroughly and approved by the Engineer.
A.
B. Mixers Concrete may be mixed at the construction site, or at a central plant or wholly or in part in truck mixers under the following conditions:
l. 2.
Batching Plant Equipment
L
The batching plant should include bins, weighing hoppers and scales for the fine aggregate and for each size of coarse aggregate. The weighing hopper shall be properly
2.
The batching plant should be equipped with a suitable non-resealable batch counter, which will correctly indicate the number of batches and proportioned.
3.
Bins with adequate separate compartrnents for fine aggregate and for each size of coarse aggregate should be provided in the batching plant.
4.
4.
for weighing aggregates and cement should be of either tlre beam type or the spring less-dial type. They should be accurate within one half percent throughout the
5.
range ofuse.
6.
274
The batching plant should be equipped with automatic weighing devices of an approved type 1o proportion aggregates and bulk cement.
The mixer shall be equipped with approved timing devices, which will automatically lock the discharge lever when the drum has been charged and released at the end of the mixing period. In case of timing device failure, the mixer may be used for the balance of the day while it is being repaired, provided that each batch is mixed in 90 seconds.
Scales
Poises should be designed to be locked in any position and to prevent unauthorized change. Scales shall be inspected and sealed as often as the Engineer may deem nscessary to assure their continued accuracy.
Mixers at site of constructioz - Mixing should be done in an approved mixer capable of combining the aggregates, c"-*t and water into a thoroughly mixed and uniform mass within the specified mixing and dischargirrg and distributing the mixture without segregation on the prepared grade.
3.
sealed and vented to preclude dusting operations.
5.
Each mixer shall have a manufacturer's plate attached in a prominent place showing the capacity of the drum in of volume of mixed concrete and the speed of rotation of the mixing drum or blades.
C.
Truck mixers to be used for mixing and hauling concrste NA Truck Agitators used for hauling central mixed concrete shall conform to the requirements of AASFIIO Mr57. Non-Agitator Trucla. Bodies of non-agitating hauling equipment for concrete shall be smooth, mortar-tight metal containers capable of discharging the concrete at a satisfactory controlled rate without segregation.
Paving and Finishing EquiPment
The concrete should be placed and set with an approved paver designed to spread, consolidate, screed and float finish the freshly placed concrete in one complete of the machine in a manner that a minimum of hand finishing will be necessary 215
Concrete Pavement
Elements of Roads and Flighways
to provide a dense and
homogeneous pavement. The finishing machine should be equipped with at least two oscillating tlpe of transverse screed. Vibrator should operate at 8,300 to 9,600 frequency of impulse per minute under load at a maximum spacing of 60 centimeters.
D. Concrete Saw Cr:ncrete saw should be rvater-cooled diamond edge saw blade or an abrasive wheel conforming to the required dimensions and rate ofspeed.
If loss of densitv results from the trimming operatrons, i1 should tre restored by additional compaction before concrete is placed. If any traffic is allowed to use the prepared sub-grade or the surface. it should tre checked and corrected immediately ahead of the placing ol' concrete. The sub-grade or base should be
unifonnly moistened when the concrete is placed.
Setting of Forms
l.
grade. Any roadbed, which is below the established grade, should be filled with approved gramrlar materials to grade in lifts of three centimeters or less, and thoroughly re-rolled or tarnped. hnperfections or variations above the grade should be corrected by tamping or by
E. Forms
l. 2 3.
Forms should be made of an approved steel section with a depth equal to the thickness of the pavement at the edge. The base of the form should be of sufficient width to provide necessary stability in all directions. The flange braces must extend outward of the base not less than 2/3 of the height of form. All forms should be rigidly ed on bed during the entire operation of placing and finishing the concrete. It should be provided with adequate devices to secure its setting so that when in place, they will withstand without visible spring or settlement the impact and vibration of consolidating and finishing of the concrete pavement.
cutting as necessary.
2"
After the base or sub grade have been placed and compacted areas that will the paving machine and the grade on which the pavement is to be constructed should be trimmed to the proper elevation by means of a properly designed machine extending the work at least 60 centimeters beyond each edge of the proposed concrete pavement.
Grading ond alignment- Form shall be set suffrciently advance from the point where the concrete is being placed. After setting to correct grade, the base is thoroughly tamped, mechanically or by hand, at both edge of the form base inside and outside. The forms should not deviate from the true line by more than one centimeter at any pornt.
3.
8-15 Preparation of Grade to the required density, the
Base Suppnrl -The foundation under the forms should be hard and true to gracle, so that the form when set wili be fitmly in with its whole iength at the specified
Grading and Alignment - T"he alignment and grade elevation of the forms should be checked and corrections be made irnmediately before the placing of concrete. Prior to the placing of concrete, the crown and elevation are verified by holding an approved template in a vertical position moving backward and forward on the forms.
Conditioning the Sub grade or Base Course
l.
When the side forms have been security set to grade, the base-course should be brought to proper cross section. High areas are trirnmed to proper clevation and low areas ')"7
276
l
Elements of Roads and Highways
2.
Concrete Pavement
are filled and properly compacted. The finished grade should be maintained rn a smooth and compacted condition until the concrete is placed. Unless waterproof base course material is specified, it should be uniformly moistened when the concrete is placed. If it subsequently becomes too dry, the sub-grade or base course is sprinkled with water, but the method of sprinkling should not form mud or pools of water.
cordance with AASHTO M-157 requlremenrs, except that the minimum required revolutions at the mixing speed for transit mixed concrete may be reduced to not less than that recommended by the mixer manufbcturer. The number of revolutions recommended by the mixer manufacturer should be indicated on a serial plate at_ tached to the mixer
2.
When n,ixing is done at the site or in a central mixing plant, the mixing time should not be less than 50 secondi nor more than 90 seconds, unless mixing performance tests provide adequate mixing of the concrete in a shorter tune period. Mixing time ends when the discharge chute of the mixer opens. The contents of the rndividuil mixer drum shall be removed completely before a succeedins batch is loaded thereln
3.
The volurne of concrete mix per batch should not exceed the mixers nominal capacity in cubic meter, as indicated on the manufacturers standard rating plate attached on the mixer except that an overload up to l0 o% above the mixers normal capacity may be permitted provided that concrete test data"for strength, segregation and uniform consistency are satisfied and no spoilage of concrete
8-16 tlandling, Measuring and Batching of Materials The batching plant and equivalent layout must provide a srnooth flow of continuous supply and transport of materials to the work. Stockpiles are built up in layers of not rnore than one meter in tldckness with each layer completely in place before beginnrng the next that should not be allowed to "cone" down over the nexl lower layer.
All
washed aggregates and aggregate produced or hand,led brnned for draining at least trvelve hours before being batched.
by hydraulic methods are stockpiled or
The mixer should be charged without loss of cement and batched material should be weighed for each material required within a tolerance of one percent for cement and two percent for aggregates. Water may be measured by volume or by weight and the accuracy of measuring water shall be within a range of not more than one percent error.
should take place.
4.
The batches shall be charged into the drum with a por_ tion of the mixing water enter in advance of the cement and aggregates. The flow of water should be uniform that all water shall be inside the drum by the end of the first
l5
seconds of the mixing period.
Mixing Concrete
5.
The concrete may be mixed at the site, in a central plant or by truck mixers of approved type and capacitl'. Mixing time will be measured from the time when all the materials except water
6. Mixed concrete from the central
are already inside the drum.
l. 278
Ready mix concrete shall be mixed and delirered in ac-
The throat of the drum shall be kept free of concrete ac_ cumulatjon that may restrict the free flow of materials into the drum.
mixing plant shall be transported in truck mixers, truck agitators, or non_ agitating trucks. The time elapsed from the time water is added to the mix until the concrete is deposited in place )79
Concrete Pavernent
Elements of Roads and Highways at the site shall not exceed 45 minutes when the concrete is hauled in non-agitating trucks, nor 90 minutes when hauled in truck mixers or truck agitators. except that in hot rveather or under other conditions contributing to quick hardening of concrete, the maximum allowable time may be reduced by the supervising Engineer.
7.
constructed lane, and mechanical equipment
3.
Vibrators shoultl not be allowed to come in with a t assembly, grade or side form. In no case it be operated longerthan 15 seconds in any one location'
4.
Concrete should be deposited as near as possible to the expansion and contraction ts wilhout disturbing them, but should not be dumped from the discharge bucket or hopper into a t assembly unless the hopper is well
Re-tempering concrete by adding water or by any other means shall not be permitted, except that when concrete
is
delivered in truck mixers, additional water may be added to the batch materials and additional mixing is per-
will be oper-
ated upon the existing lane, that previously constructed lane must have attained the strength for 14 day concrete' If finishing equipment is carried on the existing lane paving in ading lanes may be permitted only after 3 days'
form increasing the slump to meet the requirements if permitted by the Engineer, provided that all these operations are performed within 45 minutes after the initial mixing operations and the water cement ration is not ex-
centered on the
t assemblY.
ceeded.
Concrete t
Limitation of Mixing
No concrete should be mixed, placed or finished, when natural light is insufficient, unless an adequate and approved artificial liglrting system is operated. 8-17 Placing or Depositing of Concrete in such a manner requiring minimal re*handling. Unless truck mixers or non-agitating hauling equipment are equipped with a means to discharge concrete rvithout segregation of the materials, the concrete should be unloaded inside the form in a manner to prevent segregation of Concrete
is
deposited
the particles.
L
2 280
Placing of concrete between transverse ts without the use of intermediate bulkheads. Necessary hand spreading shall be done with shovels, not rakes. Workers are not allowed to walk on. Where concrete is to be placed ading a previously
Concrete ts are constructed according to the type' dimensions and at the locations as indicated on plans or special provisions.
All ts should be protected from the intrusion of injurious foreign materials until after sealed. Concrete pavement ioints are classifed into:
l. 2. 3. 4. 5.
Longitudinalt Transverse t
Transverse construction t Transverse construction t
Loadtransfer device
Longitudinal t
l.
Deformed steel bars or special length, size, spacing and materials are placed perpendicular to the longitudinal ts. Tie bar should not be painted or coated with asphalt or otier materials or enclosed in tubes or sleeves' 281
Elements of Roads and l{igtrways
2.
Except those made of rail steel, tie bars maybe bent at right angles against the form of the first lane constructed and straightened into final position before the concrete of
the adjacent lane is placed.
3.
4.
Concrete Pavement
The longitudinal ts are sawed before the end of the curing period or shortly thereafter and before any equip_ ment or vehicles are allowed on the pavement. The sawed area should be thoroughly cleaned and if required the t should be filled immediately with sealer.
The tool or device remain in place at least until the concrete has attained its initial set, and to be removed without disturbing the adjacent concrete.
3.
concrete hardened sufficiently to permit sawing wilhout excessive ravelling, and the time is usually within 24 hours.
Longitudinal pavement insert type ts should be formed by placing a continuous st ip a plastic material which will react adversely with the chemical constituent ofthe concrete"
2. 3.
a)
ts are sewed before uncontrolled shrinkage
b)
cracking takes place. If necessary, the sawing operations should be car-
c)
Transverse Expansion t
l.
Sawed Contraction t is made by sawing groove in the surface of the pavement. Sawing is done as soon as the
The expansion t filler should be continuous from form to form shaped to the sub-grade and to the key_way along the form. Pre-formed t filler should be furnished in lengths equal to the pavement width or equal to the width of tt.
d) e)
lane.
Finished
t should not deviate more then 6 mm from a If t fiflers are assembled in sections.
straight line.
there should be no offsets between adjacent units. concrete should be permitted anywhere within the expansion space.
4. No plugs of
t is classified into:
l.
Transverse Strip Contraction t is installing as parting strip to be left in place as specified.
2.
Formed Groove is installed by depressing an approved tool or device into the plastic concrete.
282
weather conditions.
The sawing of any t is omiued if crack occurs at or near the t location prior to the time of sawing.
Sawing should be discontinued when crack develops ahead of the saw. In general, all ts should be sawed in sequence. If extreme condition exists making it impractical to prevent erratic cracking by early sawing, the contraction t groove is formed prior to the initial setting of concrete.
Transverse Contraction t
l.
Transverse contraction
2.
No Transverse t should be located within 1.50 meters of an expansion t, contraction ! plane or weak-
Transverse Contraction t The transverse contraction
ried on during the day or night regardless of
t is provided when there is art interruption of more than 30 minutes in the concreting operations.
ness.
has been mixed at the right time of intemrption to form a slab of al least 1.50 meters long the excess concrete from the last preceding t should be removed and disposed of as directed
3. If sufficient concrete
283
Elements of Roads and Highwtys
Concrete Pavement
Load Transfer Device
8-1S Final Consolidation and Finishing
Load transfer device is provided along the longitudinal centerline of the pavement either by tongue and groove concrete or by steel dowels under the following considerations: When dowel is used, it should be held in position parallel to the surface and centerline of the slab by a metal device that is left embedded in the pavement. 2.
J.
The portion of each dowel painted with one coat of lead or tar should be thoroughly c
The sequence of operations after placing the concrete at grade is the strike-off or consolidation, floating and removal of laitance, straight edging, and final surf,ace finishing. L Addition of water to the surface of concrete in order to assist in finishing operations should not be permitted. However, if the application of water to the surface is allowed, it should be applied as fog by means of approved sprayer equiprnent. z.
'lhe sleeves for dowel should be rnetal, design to cover 50 mm plus or minus 5 mm of the dowels with a water tight closed end with a suitable stop to hold the end of
pavement.
the sleeves at least 25 mm from the end of the dor,vel.
Concrete, adjacent to ts, should be mechanically vibrated. The finishing machine is brought forward operating in a manner to avoid damages or misalignment of
ln lieu of using dowel assemblies at contraction ts, dowels may be place in the fulI thickness of the pavement by a mechanical device approved by the Engineer.
ts. 4.
If the unintemrpted operation of finishing machine over beyond the ts causes segregation of concrete, and misalignment of the ts, the finishing machine should be stopped when the front screed is approximately 20 centimeters from the t.
5.
TABLE 8-6 RECOMMENDED DIMENSION OF'DOWEL FOR CONCRETE PAVEMENT
Centimeters
Dowel Diameter mm
15.0
20
45
30
t7.5 20.0
25 25
45 45
30 30
22.5
32
45
30
25.0
32
45
30
The front screed should be lifted and set directly on top of the t and the forward motion of the finishing machine is resumed. When the second screed is closed enough to permit the excess mortar in front of it to flow over the t, it should be lifted and carried over the
27.5 30.0
32
45
30
t
32
45
30
Pavement Thickness
Source: AASHTO
284
Dowel Length
Dowel Spacing
Centimeters
Centimeters
The concrete placed adjacent to ts shall be compacted and firmly set wilhout voids or segregation under and around the load transfer devices, t assembly units, and other features designed to extend into the
Interim Guide and proposed revision 1980
6.
Thereafter, the finishing machine may be run over the t without lifting the screeds, provided ttrat there is no 285
Concrete Pavement
Elements of Roads and Highways segregated concrete immediately between the
t and
2. In a narrow width or areas of irregular dimensions
where operations of the mechanical equipment are impractical, hand methods may be used.
the screed or on top of the t.
Finishing Machine
3.
Concrete as soon as placed is struck off and screeded by an approved portable screeder. The screed should be at least 60 cm. longer than the maximum width of the slab to be struck off.
4.
Consolidation should be attained by the use of suitable vibrator or other approved equipment.
5.
On finishing operations, the screed is moved fonrard on the forms with a combined longitudinal and transversal shearing motion.
6.
Movement is always in the direction where the work is progressing and manipulated that neither end is raised from the side forms during the striking off process. If necessary, this should be repeated until the surface is of uniform textures, true to grade and across section, free
Non-Wbratory method - The concrete is distributed and It is struck off and screened by an ap-
spread as soon as placed.
proved frnishing machine. The machine goes over each area of pavement as many times and at such intervals as necessary to give the proper compaction and leave a uniform texture surface.
l.
2.
Excessive machine operation over a given area should be avoided. The top of the forms should be kept clean by an effective device attached to the machine and the travel of the machines on forms should be maintained true to grade without wobbling or otlrer vibration tendrng to affect the precision finish.
During the first of the finishing machine, a uniform ridge of concrete should be maintained ahead of the front screed in its entire lensth.
3. If uniform and satisfactory
density of the concrete is not obtained by the vibratory method at ts along the forms of the structures, and throughout the pavement, the contractor will be required to furnish equipment and method that will produce pavement conforming to the specifications.
ofporous areas. Floating
1.
chanical method.
2.
The hand operated longitudinal float should not be less than 3.60 meters long and 15 centimeters wide properly stiffened to prevent flexibility and warping.
3.
The longitudinal float is operated from a footbridge
Hand Finishing Hand finishing methods may be used under the following conditions:
l.
286
In the event of mechanical equipment breakdown hand methods may be used to finish the concrete already deposited on the grade or form.
After the concrete has been struck off and consolidated, it is further smoothened, trued and consolidated by means of a longitudinal float, either by hand or by me-
resting on the side forms and spanning but not torrching the concrete. Working with a sawing motion while held in a floating position parallel to the road centerline, and moving gradually from one side of the pavement to the other side. 287
Elements of Roads and Highways
4.
5.
The movement ahead along the centerline of the pavement should be in successive advances of not more than one half length of the float. Any excess water or soupy material is wasted over the side forms on each .
Concrete Pavernent
Final Finish
l.
The track from where the mechanical float operates should be accurately adjusted to the required crown and
float also accurately adjusted and coordinated with the transverse finishing machine so that small amount of
Ping.
Z. "fhe brooming
operation is executed by producing uniform appearance of comrgations produced in the surf;ace not more than I 5 ryn dePth.
mortar is carried ahead of the float at all times.
6.
The float should over each area of pavement at least two times. Excessive operations over a certain area should not be permitted. Any excess water or
3.
soupy material should be wasted over the side forms on each .
Straight Edge Testing and Surface Correction
l.
After the floating work and excess water removed, while the concrete is still in plastic condition, the surface ofthe concrete is tested for correctness by a 3.00
4.
The straight edge bar is held in with the surface
in
'
3.
wi&h.
5.
Advances along the road should be in successive stages of not more than one half the length of the straight edge bar. Any depression found or noticed should be filled immediately with freshly mixed concrete, consolidated
Hand belt must have suitable handles to permit a controlled uniform manipulation. The belt is operated with short strokes transverse to the centerline with a rapid advance parallel to the centerline.
6.
If the surface texture is drag fnished, use a drag, which consists of a seamless strip of damp burlap, or cotton fabric, which will produce a uniform gritty texture after dragging it longitudinally along the full width of the
The surface across the ts must strictly meet the requirements for smootluress. The Straight Edge testing should continue until the entire surface is found to be free from humps and noticeable departures from the straight edge bars.
288
surface texture is belt finished, after straight edging and the water sheen has practically disappeared, and just before the concrete becomes non plastic, the surface is belted with a 2-ply canvas belt not less than 20 cm. wide and at least 100 cm. longer than the pavement
If the
successive positions parallel to the road centerline and the whole area gone over from one side of the slab to the other as necessary.
and finished.
4.
Brooming should be completed before the concrete is in such condition that the surface will be unduly roughened by the operations. The finished surface should be free from rough and porous areas, irregularities, and depressions, resulting from the improper handling of the broom.
meters long straiglrt edge bar.
2.
If the surface texture is broom-fnished, it should be applied when the water sheen has practically disappeared. The broom should be drawn from the center to the edge of the pavement with adjacent strokes slightly overlap-
pavement.
7.
For pavemcnt 5 meters or more in width, fhe drag is mounted on a bridge, which travel on the forms' The burlap or fabric 1.00 meter wide is in wrth the 289
Elements of Roads and Highways
Concrete Pavement
full width of the pavement surface while dragging.
8.
of more than 3 mm but not exceeding 12 mm in 3.00 meters spar is marked and immediately ground down with an approved grinding tool to an elevation where the area or spot will not show surface deviations in excess of 3 mm when tested with the 3 meters straight edge.
The drag shall consist of not less than 2 layers of burlap
with the bottom layer approximately 15 centimeter wider than the layer. It should be maintained with a resultant surface uniform in appearance free from grooves
over 1.5 mm. Drags should be maintained clean
and
free from encrusted mortar. Regardless of tlre methods used in final finishing work, the hardened surface pavement must have 0.25 coefficients of friction or more. Completed pavement found to have coefficient of friction less than 0.25 should be grounded or scored by the contra;tor at his expense to provide the required coefficient of fric-
tion.
Edging at Forms and ts
1.
2.
After the final finished, but before the concrete has taken its initial set, the pavement edges along its side of the slab and all ts, transverse construction ts, and emergency construction ts, shouid be worked with an approved tool and rounded to the radius required.
Any tool marks appearing on the slab, adjacent to the ts should be eliminated by brooming the surface. But in so doing, the rounded slab corner should not be disturbed. All concrete on top of the t fillers should be removed completely.
3.
All ts are tested with a straight edge and corrected if one edge of the t is higher than the other before the concrete completely set.
Surface Test
l. 290
2.
Where the departure ftom correct cross section exceeds 12 mm, the pavement should be removed and replaced by the contractor at his expense.
3.
Any area or section that was removed should not be less than 1.5 meters in length and not less than the full wrdth of the lane involved.
4.
When it is necessary to remove and replace a section of the pavement, any remaining portion ofthe slab adjacent to the ts that is less than 1.5 meters in length should be removed and replaced.
8-19 Curing Immediately after the finishing operations and the concrete has sufficiently set, the entire surface of the newly placed con-
crete is cured in accordance with either one of the following methods:
1. 2. 3. 4. 5.
The use of cotton or burlap mats. The use of waterproof paper.
Straw curing.
By impervious membrane method. By use of white polyethylene sheet.
Cotton or Burlap Mats. The pavement surface is entirely covered with mats thoroughly saturated with water. The mat is
The pavement surface is tested with a 3-meter straight
placed and weighed to remain in intimate with the pavement and maintained fully wet in its position for 72 hours
edge or other specified device. Areas showing high spots
unless otherwise specifi ed.
291
Elements of Roads and Highways
Concrete Pavement
Waterproof Paper. The top and sides of the pavement is covered entirely with waterproof paper. The units are lapped at least 45 centimeters placed and weighed dorvn to remain in intimate with the surface cover. ts are securely sewed or cemented together not to open up or separate during the curing period. The cover should be maintained in place for 72 hours after the concrete has been placed. The surface of the pavement is thoroughly wetted prior to the placing of the paper.
The units are lapped to at least 45 centimeters placing the sheet rveighed down to remain in with the surfbce covered. The slieeting shouid extend beyond the edges ofthe slab at least
Straw Curing. When straw is used for curing, the pave* ment rs cured initially with burlap or cotton mats until after the final set of concrete or in any case 12 hours after placing the concrete. As soon as the mat is removed the surface and the sioes of the pavement is thoroughly wetted and covered with al least 20 cm. straw or hay measured after saturation of water to last for 72 hours. Impervious Membrane Method - The entire surface of the pavement is sprayed uniformly with white-pigmented curing compound, immediately after the finishing of the surface and before the setting of concrete has taken place. The curing compound is not applied during rainy days. The spraying equipment is equipped with a wind guard and the time and of use, the compound is thoroughly mixed with the pigment uniformly dis-
twice the thickness of the pavement. The covering sirould be maintained in place for 72 hours after the concrete has been placed.
8-20 Rernoval of Forms Fonns for concrete pavement should remain in place undisturbed within 24 hours after pouring. The removal could be done as follows:
l. 2. 3.
Crorvbars are used in removing fonns, pulling out nails and pins but care should be exercised not to break the pavement edges. In case a portion of thc concrete slab is spelled off. it should be repaired irrunediately ivith fresh mortar mix-
ture of 1.2.
Major honevcombed area ilill be considered as defective rvork, to be removed and replaced.
Protectiorr of pavernent
persed throughout the vehicle.
During the Application, the compound is stirred continuously by an effective, mechanical means. Hand spraying of odd widths or shapes and concrete surface exposed by the removal of forns will be permitted.
'lhe curing compound
should have that property to harden within 30 minutes after application Should the film be damaged from €ury cause within 72 hours curing period, the damaged portion shall be repaired immediately with additional compound.
White Polyethylene Sheet. The top surface and sides of the pavement is entirely covered with white polyethylene sheet.
292
Concrete pavement and its appurtenances should be protected against public traffic. and traffic caused b), the workers Protection of the pavement includes the posting of watchmen to direct traffic and the posting and maintenance of warning signs. lights, pavement bridges or crossovers, etc. Anv damage to the pavement prior to the final acceptance of the rvork shall be repaired or replaced depending upon the extent ofthe damaged.
8-21 Concreting by the Stip-Form Method
lf
the contract calls for the construction of concrete pave-
nrent r,vithout r"rsing a fixed fbrm. the follon'ing shall applv
.l9
r
Elements of Roads and HighwaYs
Concrete Pavement
The grade. After the grade or base have been placed and compacted to the required density, the areas to the paving machine is cut to proper elevation by means of properly desrgn machine. The base on where the paventent is to be con-
starting of the paver held to minimum. If for any reason, it is to stop the forward movement of the paver machinethe vibratory and tamping elements are also put to stop immediately. No tractive force is applied to the machine, ex-ept those that are also controlled from the machine.
structed is brought-up to proper profile.
If tl-re density of the base is disturbed by the grading operation, it should be corrected by additional compaction before the pouring of concrete. The grade or base should be prepared suf'hci"ntiy advance of the concrete pouring. If any traffic is allowed io ,rr. the prepared grade, it should be checked and corrected immediately before the placing of concrete'
Placing of concrete. Concrete is deposited inside the form using an approved Slip-Form Paver designed to spread, consolidatc. screed and float finish the freshly placed concrete ln one complete p;lss of the machine. in such a manner that niinimum hand finish is obtained, yet provide a dense and homogeneous pavement in conformity with the specifications'
necessary
Protection Against Rain
To protect the concrete pavement against rain, the contrac_ tor is required to have available at all times materials for protection consisting of standard metal forms or plunks having nominal thickness of not less than 50 mm and a nominal width of nor less than the thickness of the pavement at its edge for the protection of the pavement edges and covering miterial ,,r"h *. burlap or cotton mats, curing paper or plastii sheeting materials for the protection r:f the pavement in case of rain. Acceptance of Concrete
The machine vibrates the concrete fuIl width and depth of the strip being placed. Vibration is accompanied by a vibrating tubes or arms working in the concrete or with vibrating screed or pan operating on the surface ofthe concrete'
The strength level of concrete will be considered satisfactory if the average of all sets of 3 consecutive strength test re_ sults equal or exceed the specified strength fc and no individual strength test result is deficient by more thm l5o/o of the
The sliding forms are rigidly held together laterally to prevent it from spreading. The forms are trailing behind the paver for a distance that no appreciable slumping of the concrete will occur and that necessary final finishing can be accomplished while the concrete is still within the forms Any edge slump of the pavement exclusive of edge rounding in excess of 6 mm is
Concrete which does not satisfy the above criteria, may be rejected unless the contractor could provide evidence, by mlans of a core tests thai the quality of concrete represented by the failed test result is acceptable in place.
corrected before the concrete hardens.
The concrete is held at a uniform consistency, having a slunrp not more than 40 mm. The Slip F-orm I'aver is operated nearly as possible to a c.ontinuous forward movement with all operations from mixing, delivering and spreading concrets are rrlell coordinated to provide uniform progress wrth stopping and
specified
fc.
At least 3 representative
cores are taken from each member of concrete area in place that is considered deficient. core locations should be determined by the supervising engineer so that. there rvill be least impain,ent of the strength of itructure. The obtaining and testing of drilled cores shall be in accordance witlr AASHTO T -24 requirements. Concrete in thr: area represented bv the core rvill be consi_
Concrete Pavement
Elements of Roads and Highways dered adequate
least 85olo
of
ifthe
fc
normal lot length, lot.
average strength of'the cores is equal to at
and
if no sinsle core is less than '15o/o of the
specified strength.
4. Other areas like
it
shoulo be included in the previous
intersections, entrances, crossovers,
will be grouped together to form a lot. Each lot will be divided into 5 equal segments and one core will be obtained from each segment in accordance with ramps> etc.,
If the strengih of controlled specimen does not meet the requirements, and it is not feasible or not advisable to obtain cores from the structure due to structural considerations, payment of the concrete will be made at an adjusted price due to strength deficiency of concrete specimen as specified.
AASHTO T-24 reouirements. Pavement Thickness
It is the intent of this specifications to set pavement into Deficiency Strength of Concrete Specimens in percent
Percent of Contract
Price allowed
Less than 5 5 to less than 10
l0 to less than
ln calculating the average thicliness of the pavement. individual measurement in excess of the specified thickness by more than 5 mm, and measurements less than the specified thickness by more than 25 mm, should not be included in tire average thickness.
100
15
15 to less than 20
20 to less than25 2,5 or more
80 70 60 50 0
When the average thickness of the lot is deficient, the contract unit price will be adjusted to the thickness in accordance with the paragraph below re Adjustment for thiclmess.
8-22 Talerance and Pavement Thickness
Individual area within the segnrcnt found to be deficient in thickness by rnore than 25 mm rvill be evaluated by the supervising engineer, and if in his judgment the deficient areas warrant removal, it must be removed and replaced
Thickness of the pavement will be determined by measuring the core from the completed pavement in accordance with AASHTO T-l 48 requirements.
i.
a
uniform thickness as planned for the average of each lot as defined.
by the contractor at his expense.
The cornpleted pavement will be accepted on a lot basis. A lot is considered 1000 linear meters of pavement slab rvhen a single traffrc lane is poured or 500 linear meters rvhen two lanes are poured concurrently.
2.
The last unit in each slab constitute a lot in itself when its length is at least I .2 of the nominal lot length.
3.
tf the lerrgth of the last unit rs shorter than
112 of the
nor-
4.
When the measurement of an\. core is less than the specified thickness bv more than 25 mm, the actual thickness for pavement in the area u,ill be determined by taking additional cores at no less than 5 meters interval parallel to the centerline in such direction from the affected location until a core is found in each direction which is not deficient in thickness bv tnore than 25 mm.
2el 2()(\
Elements of Roads and Highways
Adjustment for Thickness
CHAPTER
When the average thickness of a pavement per cient, payment for the lot will be adjusted as follows: Deficiency in the average thickness
lot is defi-
price lot
per lot (mm) 0-5
ROAD MAINTENANCE
Percent ofcontract
i00% paynnent
6-10 I t-15
95 85
t6-20 2t-25 More than 25
70 50 Remove and replace
9-l
Highway Maintenance
Highway mainte,lrance begins just after the construction, ,""onttrortion or rehabilitation of the roadway facilities. As defined by AASHTO; "Maintenance is the preservation 1n-d keeping if each type of roadway, roadside, structures and faciifie; a; nearly as possible in its original condition as con' structed or as subsequently improved the operation of highway safe transporfacilities and services to provide satisfactory and tation."
Methods of Measurement The area to be paid under this item is the area in square meter of the concrete pavement placed and accepted in the completed pavement. The length is measured horizontally along the centerline of each roadway or ramp. Curb and gutter will be included in the area of concrete pavement measured. Opening to Traffic The project engineer will decide when the pavement may be to traffic. The road will not be opened to traffic until after test specimens molded and cured in accordance with AASHTO T-23 have attained the minimum strength requirements. If such tests are not conducted prior to the specified age of the concrete, the pavement will not be opened to traffic until after 14 days from the time concrete was placed. Before opening to traffic, the pavement should be cleaned and ts completely sealed. opened
798
Objectives of Highway Maintenance
1.
2. 3.
Highway programs and activities are measured by the amount of expenditures for construction of new facilities and reconstruction of existing structure with the aim of keeprng up withthe traffic demand. Maintenance has its own role: by giving priority to local, rural and urban facilities particularly the paving and rehabilitation after the construction has been completed' Maintenance is focused on the do betterment proiects' It includes grading and paving for short alignment changes, to correct steep grades or sharp curves, re-surfacing and mulching, planting, flood and erosion control'
Relationship
1.
b
etw een D esign, C on stru
ction and Maintenan ce
Poor preparation of the base, insufficient slab thickness and poor mixture ratio will only result to the very expensive road repair. lndeed, management absorbed the end result of design and construction inefEciency' 299
1'l
/
Elements of Roads and Highways
2. 3. 4. 5.
Road Maintenance
Poor drainage design will mean ernsion or deposition of materials that requires costly clean up operations. Sharp ditches and steep slopes require costly manual labor maintenance as compared to flat ditches and slopes that allow equipment to work at a lower cost. Narrow road lanes usually forced large and heavy vehicles to travel with one set of wheels near the edge or off the pavement, giving the maintenance personnel serious problems in the care of pavement edges and the shoulder. High maintenance cost is the result of poor design or construction methods. This is the main problem that causes numerous demolitions and unending reconstruction ac_ tivities being undertaken by the highway people.
pen'tiic and irnmediate correclion of involves making the facilities as near the newly constructed or reconstrusted conditions as possible. The utilization of manpower is what makes the mainte'ance very costly. cost could be reduced substantially, if rnaintenance operations are done by the use of equipment. Unforfunately, rnstead of using modem equipment as a product of modern technology, Highway Managernent retum to the use of primi_ tive tools the like of traditional pick, shovels, hoe, sclthe, axe Maintenance calls for
unlbvorable conditions.
It
2. 3. 4.
Shoulder and approach maintenance Bridge mai.rtenance
Traffic services.
Road Surface Maintenance Unlike construction involving high volume of work, maintenance operation, deals with small amount of work at separate
locations. Road maintenance requires speed performance to cause the least possible disruption and danger to traffic. Maintenance operations requires:
1. 2. 3. 4.
For Gravel Roads, blading and periodic re-shaping or resurfacing is a routine periodic maintenance activity.
Ror Surface Treotment of low q/pe bituminous pavement, maintenance could be patching, seal coating, remixing and relayrng.
For Slick Asphalt Surface, roughening, burmng or nonskid seal is required. For Concrete Road, maintenance could be removal and replacement or filling of damaged areas. Sometimes t sealing or mud-jacking or under-sealing is relatively common maintenance work.
or machete. One particular example is the Community Employment Development Program (CEDP) with main objective girrlrrg e*-
ployment
to the people of the rural
"f amount areas. Large
of
money were spent for the purchase of traditional primitive tools and for manpower payroll disbursing seve'al miliions for nothing except for political gimmicks.
The projects were summarily sacrificed when 50% of the appropriation was spent for labor payroll without accomplishment.
Maintenance is Categorized into:
l.
Road Surface maintenance
Maintenance of Shoulder and Approach Maintenance of the shoulder and approaches of the highway is governed by the surface characteristics in the area.
1. 2. 3. 4.
Sod shoulders should be removed and periodically bladed down to the roadway elevation to avoid entrapment of water in the traveled way. Grass prevents shoulder erosion. If necessary, fertilized, re-seeded, or treated to keep them in good conditions. Gravel and earth shoulder should be maintained by blading under favorable weather conditions.
Rutting or setting of the shoulder should be corrected at once by reconstruction or re-surfacing.
300 301
Elements of Roads and Highways
Maintenance of Roadside The type and kind of roadside maintenance depends upon the following conditions
4. 5. 6.
:
l. If
the roadside is full of grass, mowing closer to the shoulder is the answer. If necessary, grass at the roadside be fertilized or treated with lime. ln some areas, re-
7.
seeding may be required.
2. If the roadside 3.
has dry grass considered as fire hazard, burning or plowing is the solution. If bushes cover the back-slope, trimrmng is necessary to
maintain clearance and sight distance. The Ingenious Machine usedfor Roadside Maintenance
concrste.
8.
Correction is to remove the concrete, clean the steel and apply new material such as polymer ccncrete. 9. Sometimes seal-out or overlay of asphalt materials are used as protective covering. 1 0. Check the bridge deck deterioration by:
a
a) Applying waterproof membranes b) Applying latex modified concrete. c) Impregnating the deck with polymers. d) ing electric currentthrough reinforcing
Mechanical sod cutter Cornbined seed and fertilizer spreader. c. Power mowers. d. Portable grass cutter
b. e.
Bushmower
I
f. Bush chopper
2. 3. 4.
Cleaning
of ditches, culvert, drop inlets and catch
to accommodate free flow of water. Removal of sediments, branches and other debris gathered attrash racks, culvert and structure entrances. Repair of eroded channels and dikes. Riprap and bank protection to prevent recrurence.
For steel bridge structure, the routine maintenance calls for cleaning by sandblasting, flame, or other means of re-
2.
painting. Cleaning and re-sealing of deck ts that are extruded or
3.
filled with dirt. Repair of drainage handrails.
302
an epoxy coated reinforcing steel
Traflic Service basins
Bridge Maintenance
l.
l. If decks are dismantled,
steel.
may be used.
Drainage Maintenance
l.
Re-surfacing of rough or slicky deck surface. Correct serious scour around the pier and abutments. Most bridges maintenance is considered specialized work. Traveling crews exclusively for bridges work alone is a function of the maintenance operations. Concrete bridge decks normally deteriorate due to deicing salts. The problem starts when the salt penetrates and corrodes the reinforcing steel that spall-off the overlaying
Maintenance operations of highway includes the traffic services like:
l. Stripping is a continuing functions 2. J. 4.
Repair of road signs. Maintenance of strest and highway light and signals. (sometime the functions of the local government) Coping up with emergencies. Personnel on patrol to keep the road open, and rescue stranded vehicles.
9-2 Maintenance Management Before, maintenance is regarded as secondary functions
of
the Highway agency. The personnel of the maintenance sections J tr--t
Road Maintenance
Elements of Roads and Highways
often felt that they are regarded as secondary class employees of the Highway agency. Indeed, the spoil system exist wherein the maintenance positions are used to pay political favors or buy patronage . Today, maintenance and its management are considered the most intricate and ever changing highway technology. Maintenance is now regarded as one of the most important part of the Highway agency considering the appropriations and expenditures involved for maintenance program. Continuous studies have been going on focused on the best mariagement, time utilization, productirity, methods and man-
2.
Two mowers working side by side accomplish less than when they work separately. Conversation time eats most of the working time.
3.
Not less thzur one and one half of two hours a day is spent unproductively for the preparatory operation and travel of the mower to the job site.
There is no specific number of mowing the road shoulder per year but normally, from one to four times depending upon the physical condition of the shoulder. Grass by nature grows faster during rainy days than on summer time.
agement on maintenance.
Studies showed ttre need for improvement on the following field.
l.
Education
2.
More detailed and careful plarming and scheduling of work and establishing standards for the level of mainte-
in management technique for
7.
Major improvernent of maintenance tools and equipment Providing a better and efficient communications. Establishing lines of authority and responsibilities. For the maintenance orgaruzation to succeed, staffrng with permanent trained and dedicated personnel is the solution.
Effective management system requires efficient, accurate and fair budgeting and reporting procedures. But how to implernent these, is next to impossible, because it is difficult to overcome varied istration, and behavioral
problems. One example is the studies made on roadside morving which shows that:
1.
The use of better equipment could accomplish mowing from 3 to 6 times as much area compared to the use of poor and antiquated tools.
:r04
l.
maintenance engrneers and foreman including its field personnel.
nance.
3. 4. 5. 6.
Requirements for Maintenance Management
2. 3. 4.
To stabilize the standard level of maintenance by setting performance standards for workers crew and maintenance units" This requires Methods Time Measurement (MTM) expected output for particular operations that are predetermined.
To develop an accurate monitoring and fair reportrng system and to compare actual work with the expected production. To develop a management system that will give efficient work scheduling assignment. To develop effective procedures, methods and machinery or organization to carry out individual maintena:rce operations.
Effective maintenance management could be achieved by gaining the enthusiastic of the personnel by educating them with the new methods plus acknowledgment of their efforts through personal recognition and by financial reward for there is a saying that we cannot live by love alone.
The roadway to the development in maintenanr:e is still far. While others have already gonefar advanced, v'e are just about to begin.
i05
Elements of Roads and Highways
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9-3 Rehabilitation
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during bad weather, heavy rain, removal of fallen trees, flood, erosion etc. Maintenance personnel are exposed to accidents, hazards during their maintenance or rehabilitation work.
On some instances, Highway agency is legally held responsible for injury to person or damages to property resulted from poor highway maintenance. Unfortunately, employees and supervisors are even charged in court, condemned and crucified by the media people prior the hearing of the case.
.E
-
Personnel who are devoted to the maintenance work are not those who just kill the time and collect their salaries. Personnel responsibility for keeping the roadrvay open to traffic moving under all conditions. Personnel rescue operation in assisting stranded motorists
Maintenance personnel deserves to be recognized and rewarded accordingly, unfortunately, these dedicated people are sometimes victims of neglect especially in the promotion and increase ofsalaries.
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Effective maintenance personnel activities are rneasured under the following criteria.
T
{s * €
Pavement rehabilitation is an activity primarily to provide good riding and skid resistance or to improve the structural effectiveness of the pavement. The FIIWA defined rehabilitation as:
" Resurfocing, restoration and rehabilitation work, restoring to the original tofn usable condition without addition to the original capacity. " According to AASHTO, the primary objectives of pavement rehabilitations are:
L 2. 3. 4. 5.
To To To To To
Elements of Roads and Highways
Road Maintenance
improve the smoothness of the road surface. extend the pavement life. improve the skid resistance of the road. construct the sections with poor foundations. improve the drainage facilities.
Reconstruction refers tp the removal of existing pavement and replacing them with a new pavement and under course.
The efficiency of the highrvay system could be rated by:
l. 2 3 4. -5
existing materials
of energy requirements.
Maintenance report. Public comments and suggestions.
Pavement Recycling is Categorize into:
l. 2. 3.
Restoration and Rehabilitation Restoration and rehabilitation work includes
:
Replacement of defective ts. Repair of spalled ts. Substantial pavement work. Reworking or strengthening of sub-base.
Recycling existing materials to improve their structural inlcgrity. Adding under drains. lmproving shoulders Removing and replacing deteriorated materials.
Pavement Maintenance refers to actions that are corrective or preventive.
i08
of
working on asphalt rnaterials, portland cement or lime.
Skrd tests.
Resurfacing is the addition of pavement layer over the existrng roadway or bridge deck surface to provide additional capacity. The additional re-surface pavement should not be less than 20 mm in thickness.
6. 7. 8.
Recycling means the repeated use
Generally, recycling contribute to the stabilization of cost conservation due to inadequate material resources and reduction
Sufficiency ratings. Accident data.
Resurfacing
l. 2. 3. 4. 5.
Overlays could be either by Portland cement or Asphalt concrete laid on arr existing pavement.
The trpe of matcnals to be used. The prooedure to be employed. The structural benefit to be gained.
The Recycling Procedures could be as follows
1. Surface Recycling consists of reworking about the top surface of asphalt pavement. It is applied for the treatment of ravelling, u'heel truck rutting, flushing and corrugations. The work includes the use of heater-planer, heater-scarifier, cold planers and cold milling. The disadvantages of their use are the presence ofnoise, heat and air pollution.
2. In place Surface and Base Recycling. This procedure involves pulverizing all existing pavement, followed by reshaping and compacting. Before relaying, the materials are upgraded with lime, portland cement or chemicals. This method is used for both asphalt and portland cement concrete pavement. One advantage of this method is the ability to increase the load carrvlng capacrty of the pavement without major changes in the grade.
3.
Central Plant Recycling is the removal of materials from the roadway, crushing them, mixing in the plant then laid and compacted with conventional equipnrent. 3u9
Road Maintenance
Elements of Roads and Highways
Both asphalt and Portland cement concrete are reprocessed to make aggregate materials for stabilization of the base course. The recycled materials when used as base courss is blended with additives lrithout heat such as Portland cement, Lime or Cutback or Emulsified asphalt. For surfacing, it is heated and then blended with new asphalt cement or recycling agents and sometimes with new aggregates. Advantages and Disadvantages of Recycling Categories
A. Surface Recycling Advantages:
L 2.
It reduces reflection cracking. Promotes bond between the old pavement and the thrn
B.
In-Place Recycling
Advantages: l. Significant structural improvements. 2" Treats all types and degrees of pavement distress. 3. Reflection cracking can be eliminated. 4. Frost susceptibility may be improved. 5. Improved riding quahty. Disadvantages: 1. Quality control not as good as from the central plant. 2. Traffic disruption. 3. Pulverizing equipment repair requirement. 4. Higher in cost.
C. Central Plant Recycling
overlay.
Provides transition between the new overlay and the existing gutter, bridge, pavement, etc., that is resistant to raveling (eliminates feathering). 4. 5.
6. 7.
Reduces localized roughness. Treats variety of types of pavement distress such as raveling, flushing, corrugations, rutting, oxidizing pavement faulting at a reasonable cost. Improved skid resistance. Minimum disruption to traffic.
Disadvantages
L 2. 3. 4. 5. 6.
Limited structural improvement. The heater-scarifuer and heater planing has limited effectiveness on rough pavement without multiple es of equipment.
Limited repair of severely flushed or unstable pavements. Some air qualrty problems. Vegetation closer to roadway may be damaged. Mixture with maximum size aggregate greater than I inch cannot be treated with some equipment.
310
Advantages:
l. 2. 3. 4. 5. 6. 7. 8.
Significant structural improvement. Good quality control Treats all types and degree of pavement distress. Reflection cracking can be eliminated. Improved skid resistance. Geometrics can be more easily altered. Better control if additional binder ar aggregate is used. Improved riding quality
Disadvantages:
l. 2.
traffic disruption May have air quality problems at plant site. Increased
Maintenance and Rehabilitation programs are based on different types ofcollected data that includes:
1. 2. 3. 4.
Surface Surface Surface Surface
roughness distress
deflection
friction or skid resistance
3ll
Road Maintenance
Elements of Roads and Highways
9-4
Definition of Surface Roughness is defined as the irregularities in the pavernent surfbce that adversely affect the riding qualrty
Surface Distress is defined as any indication of unfavorable pavement performance or signs of impending failure, or any unsatisfactory performance is a sort of failure.
Any type of distress that may be observed includes any one of thc following:
a.) Fracture
associated with load and non-load cracking.
b.) Distortion is a permanent deformation of faulting. c.) Disintegration
such as spalling, ravelling and other failure
of the pavement.
For each Distress I'ype, the corresponding damage, severity and locations are specified. All data are gathered and indicated in the survey form as a guide.
In cass cf Surface Deflection, measurement of the changes in pavement surface level between the loaded and unloaded segment is the basis for rehabilitation design strategies. TLre design strategy is to determine the structural adequacy or the ability of the pavement to resist traffic load without developing undesirable distress.
Distress observations could be
of static
deflection, steady
state of deflection or by the impact load response as determined by the Dynaflect and Falling Weight Deflection respectively.
Surface Friction is determined from gathered data identi$ing a pavement section having low coefficient of friction. There are equipment available to determine the skid number. It is measured using a locked wheel trailer (ASTM Method E-274) or by the Yaw Mode trailer where the wheels are skewed in accordance n'ith the direction of travel. -l
l,
Bvaluation and Maintenance of Concrete Pavement
Maintenance decisions are based on pavement condition data gathered from project to project basis. From these gathered
data, it is determined which project calls for maintenance or rehabilitation including the decisions required to correct pavement deficiencies. Decisions however, are made on a yearly basis.
Considering the increasing length of the roadways, the management on the basis of field observations alone is becoming difficult hence the objective method of evaluation was introduced:
L 2. 3.
Those projects that need immediate maintenance or rehabilitations are listed on the priority projects. .The type and kind of maintenance or rehabilitation required is specifred. What strategy of maintenance or rehabilitation would be adopted now and in the future to minimize life cycle costs or maxirnized the net benefits.
Maintenance of Concrete Pavement As mentioned earlier, maintenance of the roadway of any type is a routine activity. Maintenance of good concrete road could be arsued as follows:
t.
Sealing cracks of transverse and longitudinal construction and expansion ts is one recommendation where maintenance Engineers could not agree on one question whether sealing the narrow cracks is effective or not. The practice however, is to clean properly wide cracks or spalled ts then applied with sealing materials to prevent the intrusion of extraneous material. and to block the downward penetration of surface water.
3t3
Elements of Roads and Highways
For small and scattered broken surface on good concrete pavement, patching with concrete is economical. On affected portion old concrete is removed by vertical straight line cut parallel and perpendicular to the roadway centerline. For corner repair, the angle from the roadway center3.
4.
5.
6.
line should be greater than 30o but less than 60'. Sections that are removed should have a minimum area of 20 square meters. If the sub-grade appears to be weak, and doubtful to carry heavy axial load, replace it with suitable materials and compact properly. The new concrete slab should be as thick as the original pavement. Good practice demand that extra trrickness ading the old concrete be provided extending the patch under the old pavement to width and depth of l0 centimeters. Additional cement is necessary 1o produce high early strength concrete or an accelerator such as calcium chlorrde is used for patching if early use of the pavement is desired. The ideal time to make repair of concrete pavement road is in the evening. Pavement surface with spall from freezing and thawing or salt action are levelled with asphalt mixture or surface
treatment. Another method is to patch with concrete bonded to the old concrete with a cement-water or epoxy. 7. Spalled t can be repaired with cement grout containing epoxy mixed with catalyst.
Mud Jacking Mud Jacking is a maintenance method adopted to restore the sub-grade under pumping pavement and to level uneven slabs. The liquid filler is injected under the slab through drilled holes. The mud or slurry, filled all the voids that if continuously injected applying hydraulic pressure will force the slab upward. Slurry for mud jacking consists of a mixture of fine grain aggtegate, portland cement and water or iul addition of small amount of asphalt. A mixture of one part cement, and three to four parts of ground limestone, could be used as slurry for mud jacking. 314
Road Maintenance The mixture must through the pump without gumming. It must flow readily under the pavement to the smallest voids. The mixture must harden rapidly wrthout excessive shrinkage and not becoming hard and brittle. Take note that the spacing of the holes through the concrete should be planned carefully when the slab is to be lifted by pumping slurry into several holes. Frequent movement of the nozzle is necessary so that the lifting will be in small increment.
Under-Sealing Under-sealing is an alternative for mud jacking. Heated asphalt sometimes is used. The advantage of under sealing is the formation of asphalt as seal against the penetration of surf,ace water into the sub-grade.
9-5 Highway and its Environment Early roads were patterned after the railroad of the same period. The principle behind the construction of early road is to construct the cheapest roadrvay that would serve traffic under all conditions of weather without regards to its environment. Roadside development was not included in the program. Shoulders and right of way are narrow or non-existing at all. Side slopes were too steep; drainage and ditches, channels and structures were designed to protect the roadbed without regard to erosion outside the roadway limit. These crude practices in road building have brought unsightly conditions and high maintenance cost until such time that design standards were gradually modified and improved. The later development and improvement of roadway has incorporated the following features:
l.
Pleasing views and surroundings were developed sacrificing a little costs or distances to enhance driving pleasure. 315
Elements of Roads and Highways 7.
Long sweeping horizontal curves are acceptable than
3.
short curve connected by long tangents. Choppy or broken back grade line were not only flattened
but smoothened. In rough areas, the depth of cuts and filI heights were lowered to reduce scare and slope erosion to a minimum
5. 6. 7.
level.
Retaining walls are sometimes helpful and improve the attractiveness of the roadway. Modern highway now provides wide roadbeds, shallow wide gutter and ditches, flat back slope and cuts, and flat side slope on
fill.
Top ofthe cut banks and toes offills are rounded to blend rvith the original ground.
These features of the roadway give safer roadbed and a pleasing approach. Erosion occurs more slowly or prevented on flafter slopes. The result is less expense for cleaning gutters and ditches. Mowing could be done using power equiprnent that substantially reduces maintenance costs.
Wider right of way has become a necessity in roadside development for the following reasons:
l. It allows blending of the road into the natural landscape. Z. [t provides space to plant screening in front of unsightly 3.
and objectionable areas and other undesirable objects. It isolated the highway visually from its surroundings and freeing the roadside ofhazards.
Roadside is the entire right of way except the travelled way. planning roadside development, planners were conscious of In the cost maintenance including the cost of morving, trimming and cleaning. Roadside development is sometimes referred to as roadside beautification made after the road construction is completed. Roadside development without question provides a more pleasing environment for travelers, less maintenance cost and
3i6
Road Maintenance safer highways. The roadside development is under the care of the Highway agency, although there re adjacent propert-v homeowners who sometimes contribute to the beautification of their surroundings including the roadside itself for aesthetic consideration that they themselves enjoyed.
9-6 High\ryay Beautification Highway beautification is a broad term that includes activities like:
l. 2. 3.
Landscaping and roadside development within the rights of way. Improvement of strips and land adjacent to the highway for restoration, preservation and enhancement of natural beauty.
Acquisition and development of publicly owned and controlled rest area- recreation areas and sanitary areas including other facilities.
Factors that Contribute to Beautification
1. 2. 3. 4.
Good location Good design
Construction Maintenance
Outdoor Advertising The control and removal of outdoor advertising had long been controversial in the beautification of highways. A court ruling on these aspects states that: "The concept of public welfure, for the purpose of which the legislative may exercise police power, is broad and exclusive, and the value it represents is spiritual and aesthetic as well os physical and monetary. " 317
Elements of Roads and Highways
For public interest, the government should extend full assistance to the control and use of the areas adjacent to the highway by regulating the erection and maintenance of outdoor advertising signs, display or other devices within a reasonable distance from the edge of the right of way but still visible from the nrain traveled way.
Road Maintenance
To maintain balanced distribution of population and use of resources that will give high standard of living and wide sharing of life's amenities. To irnpart that all person has the responsibility to contribute to the preservation and enhancement of the environ-
6.
7.
ment.
9-7 Environmental Laws
9-8 Environmental Effect of Highways
The government had ed enough laws to protect the environment. The Environmental Laws has the following intent:
mental effects oftransportations are as follows:
1.
The govemment recognizes the impact of man's activities in relation to all components of the natural environment more particularly:
a) The influence of population growth b) The high density urbanization c) Industrial expansion d) Resource exploration e) The expandingtechnological advances f) Restoration and maintenance of environmental qualrty to the welfare and development of man.
2. 3.
The present generation must fulfill the responsibility as trustees of the environment for the succeeding generations. To assure all Filipino people of a safe, healthful, productive and aesthetically and culturally pleasing surround-
l.
Air
and noise problem
2. Traffic induced vibration 3. Accidents 4. Armoyance caused by water pollution,
dust and dirt.
Air Pollution Control Air pollution be it from fixed or mobile sources is the main concern in most urban areas. Air pollution is tlre result of progress. It comes from discharges into the air of non-reactive pollutants including carbon monoxide, sulfur dioxide, sulfates, dust smoke and lead. The highway pollution problems are two dimensions. They are:
1.
2.
of
Area wide effects of preliminary reactive pollutants. High concentration of non-reactive pollutants at points or corridors along or near highways.
ings.
4.
To provide the widest beneficial use of the environment without degradation and risk to health or other undesir-
5.
To preserve some important historic, cultural and natural aspect of our natural heritage and whenever possible an environment which uphold diversity and variety of individual choice.
318
The main objections of community complaint on snviron-
able consequences.
Motor vehicles are mainly the contributor to both forms of pollutants estimated at 70%o carbon dioxide, 50% hydrocarbon, and 30%' of nitric oxide. The area condition is acceptably worst when temperature inversions trap pollutants near the ground surface when there is little wind or no wind at all. Concentration becomes extremely high atrecting human life and even some vegetation are killed, stunted or the foliage is bumed. 319
Elements of Roads and Highways
Various approaches to reduce area pollutants were planned and employed including future approaches such as:
l. 2.
7_
By Land Use Control. One example is the limitation and control of industrial-commercial development where their construction and land use would contribute to pollution. To Lower the Emission. This is by lowering the emission of pollutant from existing machineries.
Modiftcation of the fixed existing fociliries such as substituting low sulfur coal to reduce the release of sulfur dioxide.
Lowering pollution coming .from motor vehicles that falls under the following categories:
a)
Reducing the output of pollutants by rnaking them fuel efficient and controlling pollutant output.
b)
Limiting vehicle travei by shifting travelers to
c)
other mode using electric current. Cuttrng fuel consumption and pollutant output by
d)
improving traffrc flow. A set of standard to be met by new vehicles.
Noise Control Noise is defined as unwanted sound. Noise is measured in decibels with a common unit dBA. This single unit combine sound intensities from all frequencies above 100 per second and strongly react in the human ear. Sound at ldBA level could be hardly detected by human ears, but an increase of l0 on the decibel scale means tenfold increase in intensity. In a quite residential area at nighg the ambient noise is measured from 32 to 43 dBA. The urban residen-
Road Maintenanee
In of
conversation
or
communication, these sound
level means that at 65 dBA a conversation is difficult at a distance of i.00 meter and at 75 dBA an ear has to be plugged by a finger in order to hear a telephone conversation.
Transportation noises are complexn studies showed that:
1.
Complaints are focused on interference with speech. TV viewing or sleep related to increase ofsound above anrbient noise level.
2. 3.
Increase up to 9 dBA , complaints would be widespread and there would be community reactions. Highway noises near residences at peak noise of about 70
dBA bring f'ew cornplaints, at 75 dBA, complaints are likely and 80 dBA will invite letter of petition and protest.
9-9 Construction in Relation to Roadside Del'elopment At the time of grading
operations, topsoil should be pre-
for future landscaping. Likewise, trees outside the distance limit from the travelled way, should be protected from damages caused by man and equipment. Removing of soil or fills from along the right of way called side borrow should be avoided, and borrow fills out of sight from the roadway is prefserved
erable.
Objects of interest like rocks, outcrops in cut slope or trees fill should be preserved for pleasant view. Rugged slope in borrow areas and along roadside are dressed to encourage the retum of native plants and shrubs.
at toes of
9-10 Vegetation and the Flighways
tial district at daytime limit is aboul4l to 53 dBA. In industrial areas tlre range is 48 tn 66 dBA, and in downtor,r.n commercial
Ground cover is defined as low growing herbaceous or woody plants more than one meter at maturity. Both low shrubs
areas with heavy traffrc is 62 to 73 dBA.
and vines are included
320
321
Elements of Roads.and Highways Ground cover is an alternative to grass in controlling erosion by wind and water. It also serves as insulation that reduces sloughing caused by freezing and thawing. Mat forming plants are considered best ground cover for protecting slopes and other roadside areas. There are those that root from decumbent branches and those that spread from suckers and shoots.
Other Vegetation Desirable for Roadside Protection
l.
Road Maintenance
3.
4.
Bushy dense foliage plants, and those producing litter
with great water holding capacity are considered
? 3. 4.
good vegetation to protect the roadside against erosion. The rapid growing species with inconspicuous flowers to prevent distraction and vandalism are preferred. Fire resistant plants with the abilrty to sprout after buming are much desirable. The cogon grass is one example. Plants that are subject to disease and insect damage, poisonous or irritating to the skin or that may become agricultural pest should be rejected.
For median strips and islands, erosion control is but one of the functions of ground covers. Properly selected plants prevent headlight glare without affecting distance and provide a contrasting background that also guide traffic directions. Tires and Shrubs Trees and shrubs are effective means of providing interes! variety and beauty to the roadside. Those that are native to the area are more preferred than the imported variety. The following are important tips in planting.
l. 2. 322
For rural roads, the objective is to preserve or recreate a natural foreground in harmony with a distant view. Existing well placed trees should be preserved while ugly and obstructing growth are removed. Replanting should be considered only when irregular in-
5. 6. 7
.
troduction oftrees and shrubs serve to highlight the natural beauty or where it is particular$ desirable to screen unsightly objects. Trees should be planted back a distance from the traveled way to provide recovery area for vehicles that run offthe roadway. A minimum distance of 9.00 meters from the lane edge is recommended (See "A guide for highway landscape and envi ronmental desi gn " ) Row planting along rural road is not considered a good taste. It spoils distant views with a monotonous design. The formal arrangement oftrees and shnrbs is suitable for urban freeways and expressways. Group planting creates an occasional point of interest or call attention to intersections, bridges or other point of hazard. Continuous planting is appropriate to screen unsightly roadside condrtions or to insulate residential areas frorn the road^
Avoid monotony over long stretches of the route. The solution is to group flowering trees and vines at best and appropriate locations.
9-11 Parking and Rest Area Parking turnout to accommodate stopping off the traveled way is an important adjunct to major rural highways. Wayside rest areas are necessary facilities of the highway wherein motorist stops, relaxes and use sanitary facilities. Wayside rest areas should be located on those with natural features that make the area:
1. More attractive. 2. Those that are accessible and safely located. 3. Those with sufficient area and with existing shades. Locations where public use will create fire hazard or otherq.ise affect ading property should be avoided. 323
Elements of Roads and Highways
cHAPrE"ffi
Likewise, location closer to cities and towns are not advisable, because it will just be monopolized by the town people. The site must have adequate driveways and parking space separated from the traveled way with bumper rails or curbs to confine vehicles. and
TRAFFIC ENGINEERING
if possible, provided with fence.
'
Without questions, highway rest areas are worthwhile, but highlvay offrcials and maintenance personnel object to their establishment because motorist s :re untidy and are sometimes vandals making maintenance difficult and very expensive.
-
10-l Road Traffic Signs The importance of road signs have been recognized world wide because of the increasing incidence of road accidents due to ttre volume
oftraffic
and bad habits of motor vehicle drivers.
The United Nations Conference on Road Traffic was held in Vienna, Austria on October 7, to November 8, 1968 under tlre auspices of UNESCO. The participating countries including the Phiiippines agreed on the Road Traffic conference to hdve a
sepilate conveirtion for Road Signs and Stgnals as necessary to facilitate international road traffic and to increase road safety' On June 6,1973, Presidential Decree No. 207 was issued by then President Ferdinand E. Marcos which states and partially quoted:
Wereas, th.e contracting parties to these conventions to which the Philippines is a signatory, have agreed to accept the system of tffic, road signs, signals and symbols and road markings described in said conventions and to'adopt the same as soon as possible.
for the ratif cation internationally, presigns and sigials in the Philippines, specially so, because of the intensifed government campaignfor road safety. Whereas, there is now an urgent needed
of these conventions in order to adopt icribed unifurm rules of traffc and ,oad
Whereas, the urgent need for adopting the unifurm trffic rules, road signs and signals as prescribed in the conventions is made more necessary because of the considerable number of foreigners and tourists that are now operating motor vehicles on Philippine roads.
iz5 3 ZL+
Traffic Engineering
Elements of Roads and Highways
After more than 20 years, although majority of the world countries have already applied the recommendations of the Vienna Convention, some countries like USA and the Philippines have still difficulties in implementing the international traffic system"
T'he three efficacy principles of Unifurmity, Homogeneit)) and Simplicity Ne not being inforced. Instead, a very complicated mixture of lnternational and US rules are adopted which leads to misunderstanding and consequently non-respect of the rules.
Uniformity includes the prohibition to use unofficial signs and markings.
Homogeneity requires that in the same conditions, the notices signs or markrng with the same value, sanrc importance and lcoated according to the same rules. Simplicity is to avoid superabundance of signs that over strain the drivers having the tendency to neglect the given instructions. Sometimes drivers cannot read, understand, or the meaning of the signs or markings.
Road Signs has the Following Objectives
l. 2. 3. 4.
To To To To
lead to a safest road traffic.
facilitate this traffic. indicate or to remind some particular traffic rules. inform the drivers how to use the highway.
The Different Categories of Signaling I)evices are:
l. 2. 3. 4.
Road Road
taffic
signs.
traffic signals.
Pavementmarkings. Guide posts and delineators
Road Signs are Classified into the Following Categories.
l. DangerWaming Signs 2. Intersection Signs 326
3. 4. 5. 6. 7. 8. 9.
Prescription Signs a) Prohibitive b) Obligation General Information Signs Direction Signs Agglomeration Signs Railway Crossing Signs Temporary Signs (on road works) Special Instruction Signs
Visibility and Legibility Signahng devices whether horizontal or vertically installed has the following objectives:
1.
To Inform
2. To Prevent 3. To Guide 4. Act as liaison agents between the driver and the highway alignrnent.
At night, drivers has no complete view of the highway envrronment. His only guide is the headlight. Therefore, road signs and signaling must be effective in the dark. Report of accidents revealed that for the same traffic condition, the percentage of fatalities at night is double than during daytime.
This difference can be explained only by the modification of one factor- Visibility. To be effective, road signs and signaling must be visible and readable considering human eye limit that is not adaptable at night driving
Visibility and Legibility of road signs or the
pavement
markings are dependent on three parameters.
l.
The detection
2. The identification 3. The reading 3Z I
Elements of Roads and Highways
Traffic Engineering
Detection is the minimum area in contrast with the environment perceptibility by human eye.
Valorization Principle means to use only the needed and useful signs. Too many road signs lessen its efficiency. Regula' tory and warning slgns should be installed sparingly because excessive use of these signs will only decrease their authority.
Identification is an analysis of the form and color of the road signs to understand the messages it conveys.
Reading is the fundamental role of road signs conforming alpha numerical language or by the syrnbol of information transmitted to the driver.
to
TABLE
IGI
Typ"
STANDARD FOR.DI AIYD SIZE OF ROAD SIGNS IN CENTIPTETERS
Triangle Side
Circle Diameter
Octagon
Square
Width
Side
Very Big
150
t25
t20
i05
Big Size Normal Sizc
t25
105
100
90
100
85
80
70
Small Size Very Small
70
65
60
50
50
45
40
35
Concentration Principle. Wren it is necessary that some road signs must be seen at the same time, they should be installed for the driver to see at a glance by mght and day. The signs must be set on the same post when the two indications relating to the same point are complementary. For instamce, traffic signal ahead and the pedestrian crossing. This concentration principle however, is limited bythe legibility principle.
Legibility Principle" Excessive efforts of reading or llrolrrory works cannot be requircd from the driver. The indicalions or analogical messages should be reduced, and if necessary, road signs should be properly distributed. Experienced proved that average observer caruiot see and understand at a glance more than two symbols at a time
10-3 The snrall type of road signs are used only when some difficulties prevent implementation of the normal type such as line of trees, mountainous road, reduced shoulders, small side walks and the like. The very small type is used exceptionally in cities for aesthetical considerations.
Warning (Danger) Sign
Warning Sign is used to warn traffic of potentially hazardous conditions on or adjacent to the roadway. Warning Sign is always Triangular in Shape with one Vertical Angle and dark blue symbol, rwo borders one white and red with reflectorized white background.
10-2 Basic Principle of Road Signs The basic principle of road signs is to be perceived clearly by a driver traveling at relatively high speed, whose attention is solicited by the driving requirements. To be useful, road signs must be efficient according to:
l. 2. 3. 328
Valo.rizationPrinciples Concentration Principles
Legibility Principles
There is no exception tq this rule, and the use of yellow color for background is strict$ prohibited for permanent signs. The yellow color is reserved only for temporary signals used during road construction or maintenance work.
Objectives of Warning Signs The objectives of warning sign is to attract driver's attention in the areas where his watchfulness has to increase on of the obstacles or of the dangerous points linked to: 329
Elements of Roads and Highways
Traffic Engineering
AAAA AAAA AAAA AAAA Merging
Tralic
Pedestrian
Hanging
Crossing Animal
Steep downward
road
Approaching
Steep
Two way
Bridge lpproaching Trafiic tight
crossing
upward
road
Nanowing
Slippery
Road under repair
road
road
Rough road
River ahead
Caution ialling stone Railroad crossing
1.
2. 3. 4. 5.
The highway structure such as curves, humps, dips and narowing. Conditions of the road such as slippery, falling rocks and the like. Other transport infrastructure like opening bridge, airport vicinity, railway crossing etc. The condition of vehicles and pedestrian traffic, pedestrian crossing, children area, two-lane highway after a multi-lane highway. Local circumstances such as: factory exit, quarry exit etc.
When
it is necessary to point out a potential risk,
an ad-
vanced danger warning sign is installed. The purpose is to inform the driver that he is approaching the obstacle, the dangerous point or the beginning of a dangerous zone. Road signs pointing to danger zone or intersections should indicate the let gth repeated after each intersection.
Fixed Message Signs Includes:
1.
2. 3.
Detailed direction to motorist of the freeways and warning signs regarding destination and lane occupancy. Signs to notifu motorists of the changes in directions. For low volume rural roads, only directional and kilometric signs installed at intersections and also signs for dangerous condilions.
Road signs should not carry commercial ment other than for traffic control only. There are situations where almost no signs are installed because they are being vandalized or taken away as building materials.
Installation of RegulatorT and Warning Signs Regulatory and Warning signs are installed sparingly bewill only decrease their aurhonty. cause excessive use of these signs
FIGURE 10.1 WARNING (DANGER) SIGN
330
331
Elements of Roads and Highways
LJ\ AA A^\A Dangerous Curve
Dangerous Left Curve
Dangeroue Right
Curve
Dangerou!double curve at lefi
AA
AA Dangerour right
double curve at
Waming Croas Road
Entering Crosa Roao
AA
AA Curve to
right
Curye
A A
Entering Major Crosg Road
A A'
to
lefi
Airport vicinity
Nanowed road
Traflic Engineering For oversized signs on expressway and freeways, white letter on green background with white border is recommeNrded.
Large sizes of signs are effective on expressway or where speed, hazard, accident orperie,nce or competition from lights or other signs is extreme. 3. Excessive use oflarge signs should be avoided because it makes the regular sizes less effective. 4. Non-refleclorized signs are satisfac0ory for most school zone markings, parking conaol, me,n working and other temporary warnirgs that are effective only in daytime or illuminated by street lighting. 5. The Traffic Manual suggest that two signs, one black on white, unreflec0orized and other white on black reflector' ized be mounted on the same standard where speed limits differ between day and night. 6. Signs with significance at night should be illuminated or
2,
7.
reflectorized. The sign message must be simple. The driver in so short a tinne available looking at slgn messages ciumot observe and assimilate large amount of information printed on it.
8. An expressway or freeways usually have two messages and no more than three regarding directions or destination should appear on a single signboard.
FtcuRE 1G2 WARNTNG (DANGER) StcN
Other important Place Information should be given on separate signs. At turnoffs from limited acc€ss facilities, directional sign may be used either:
l. 2.
To indicate the immediate
numzuver wit"\out dstail to
subsequent one or
To diagramthose later movemeds on earlier signs.
Effectiveness of Road Signs
R:50FIGURE
'G3 732
DETAIL OF WARNING (DANGER) SIGN
As mentioned earlier, too many signs will make all of the'rn less effective. I".arge signs overwhehn any smaller ones. Thus, signs often fail to accomplish its main purpose. For example: 333
Tra{Iic Engineering
Elements of Roads and Highways
l. Stop sign to control 2.
3.
4.
vehicle speed in residential areas are useless for being ineffective. Majority of the motorists make a roll stop and few otlers only ignore the signs. Signs like "Slow Children at PIay" have no effect on speeds. Selection of sign message is important because drivers react to them differentlv. The "Slippery When Wet" warning sign is not threatening, but effective only when accompanied by flashers. tf signs convey incorrect information such as safe speed indicator on curve warning sign suggest a speed slower
than the driver find easy and comfortable, they
will ig-
nore subsequent messages, ttrinking that the signs are
5.
only fooling them. If signs tell them tJrat there is ongoing construction or maintenance work ahead when none is actually in progress, drivers will ignore all such signs.
l0-4 Intersection Signs
right of way against the vehicle coming from the right or from the left, except as ottrerwise provided.
Priority Road: Sign 12-9 punctual warning sign of the intersections where the driver has priority against all vehicles. The thickness of the principal road is bigger to avoid confusion with another sign. Sign STOP or GIVE WAY has to be located on the other road.
s@ 3. Non-Priority
Priority Sign Pr and Pz is to inform the driver that he is driving on a priority road or street and that he has the right of waY.
Road
The driver of any vehicle entering a highway from private road shall yield the right of way to all vehicles approaching, entering or in the intersection.
III
Article of the Nght of Way and Signals of the Traffic Code is not clear. Therefore, it is necessary to define the right of way rules at the junctions and intersections. The right of way can be reduced to three possible situations:
1. General Rule.
General Rule, right priority sign W 2-1 warning sign of the intersections where the driver has to give way to the vehicles approaching or entering the intersection on the right.
2. Priority Road
734
necessary for safetY.
Sign R1-1
When the vehicles approaches an intersection from different roads, the driver on the left should yreld the right of way to the vehicle on tlre right except as otherwise hereinafter provided.
Any vehicle
@
The Stop sign is used to ensure caution before entering an intersection. A full stop is
mning onthis type of road has always
The
Rl-l
V Signs Rl
the
Sign cannot be used alone'
It is announce by Rl-
2a sign installed before the intersections like a warning sign. The GIVE WAY sign notifies the obligation of the driver to give way to all vehicles coming from right and left without the obligation to stop. The use of this sign supposes that the sight triangles are effectively implemented and maintained. lt also supposes. that the GIVE WAY sign is announce by R1-2b sign located before the intersection like a warning sign.
335
Elements of Roads and Highways
Traflic Engineering
The Philippine road signs manual (Revised Edition 1982) proposes no less than 22 traffic sign combinations for junctions and intersections. [t is too much number giving the drivers more confusion. The proposal is to use only six types of intersection signs for simplicity.
When signs are located more than 200 meters from an intersection, it should be repeated at half distance, and the two signs should be equipped with distance slgn.
Road signs located betwesn 100 meters and 200 meters be-
Exception to the Right of Way Rules
l. 2.
3.
Vehicle drivers entering a highway from private road must yield the right of way to all vehicles approaching on such highway.
Driver of vehicle upon a highway of any category must yield the right of way to police or fire deparfrnent vehicles and ambulances operating on official business and the driver thereof sounding audible signal of their approaches.
The indicatrons of traffic signals or the orders of a traffic office1 prevails against the right of way rules.
In an intersection where some flows of traffic can be in conflict, it is suggested that the drivers must be:
1.
Notified in time of the existe,nce of intersection.
2. Informed ofthe applicable rigtrt of way rules. 3. Able to see the vehicles approaching upon the other roads.
The first two prescriptions will be implemented by means road signs the third is by sight triangles.
fore an intersection do not have distance sign. Where the distance is shorter than 100 msters or greater than 200 msters it should be indicated on the distance sign' The distance is rounded to the ncarest 50 meters if it is greater than 200 meters. Between 50 and 100 meters it is rounCeci to 50 or 100. The road signs Rl-2a and R1-2b are always located with a distance sign. The distance is rounded to nearest 50 meters if it is grcater than 100 meters" Bstween 50 and 100 meters it is rounded to 50, ?5 and 100 meters. The distance signs are 1ocated under the road signs.
The roadside srgn should be mounted clear of roadside vegetation and clearly visibte under low headlight illuminatron The heigh of the sign base is 1.00 meter above the by "ight. nearest edge of the travel way but this height could be modified to improve visibility. On the intersection island, the signs can be installed less than 1.00 meter to prcvent them from masking the visibilrty.
of
Location of the Intersection Signs On Rural Areas, the normal distance between the intersections and the waming signs is 150 meters. This distance can be modified according to site conditions and the free operating speed. It can reach up to 400 msters on highways with good visibility and where the speed can be high. There are exceptional cases where two very near successive intersections can justi$ location distance shorter than i00 meters. 336
Distance Indication Sign
bstween the successive intersigns. Road signs are warning the including is variable sections preceding junction' the and intersection the located betwesn it is rounded to the 50 meters, When the distance is smaller than nearest l0 meters. On curbed roads, signs are located back from the face of the curb not less than 30 celrtimeters or more than
In Urban Areas, the distance
1.00 meter.
In Urban Areas with public illumination, tlre signs can
be
placed a|2.30 meters above the top of the curb. Where pedestriiilN or parking of vehicle is not allowed, ttre rural area rules are applicable. 337
Elements of Roads and Highwnys
Traffic Engineering
Sight Triangles
If possitrle, vehicle drivers should be given the best visibilconditierns. Thus, in deg road intersections, the Free Flow Operating Speed is considered, not the Design Speed. In approaching irrtersection, the drivers of two converging vehicles need enough visibilrty to see each other in time to prevent collision at the crossing" The sight triangle is associated to each conflict point between two vehicle fl,:ws. The summits of this triangle are the conflict point, and the limit from where the drivers must notice an adverse vehicle. ity
l||rr llrttt|t lltll trl.rilt
\\-
The signal GIVE WAY is applied only to the vehicles on the secondary road. However, it is necessary to check if the vehicles on the secondary road have the visibilrty corresponding to tJre execution at the crossing or insertion maneuver.
J6O
Forms of Intersection Signs
1. 2. 3.
Triangular in shape with one angle vertical. Triangular shape with one angle atthe bottom" Square and octagonal shape.
The triangular shaped signs with one angle vertical are following the general rules for warning signs. The triangular shaped with one angle at the bottom includes red border wider than the normal waming sign (x 1.333).
l--*-
l0-5 Prescription a,nn,
o'*r"n""
.o
FIGURE 1O-4 SIGHT TRIANGLES RIGHT PRIORIry
338
Sign
The Prescription Road Signs inform the drivers of the traffic laws and regulations that could be an offense to anyone who disregard and violate it.
Prescription sign is installed only with the approval of Public Authority having jurisdiction of the premises to be removed any time if the legal requirements of the signs become inconsistent with the prevailing conditions. 339
Traffic Engineering
Elements of Rosds and Highways Included in this classification are those signs that indicate removal of legal restrictions imposed by a preceding prescription sign.
ae
The No Left Turn - No Right Turn The turn prohibition is applicable at the next intersection. The signs can be completed by auxiliary sign M4 giving the category of vehicles.
Prescription Sign is Classified into Three Categories
The No U Turn This sign is used to notify the U-Turn prohibition up to the next intersection. This intersection is included in the prohibition.
Prohibitive Signs b) Obligation Sigrrs a)
c)
End of Prescription Signs
The prescription signs are circular in shape, but for regulatory purposes ofparking applied to a zone, the circte is placed inside a square.
1.
The Prohibitive Signs have a white background, red nng and prohibitive red bar, symbols, and letters. Numbers are dark blue except the srgn R3-l vvith red background and the Signs R5-10, R5-12 with a dark blue
The No Overtaking Sign The R3-16 sign signifies the drivers that it is prohibited to over any Vehicle except the two wheel vehicles without sidecar. The R316 sign must be completed by continuous line marking on the pavement.
@@
Stop Contrcl The R3-17 sign is used to notify the proximity of a control point where the vefricle has to stop. The sign is divided into two by a dark blue horizontal bar. On the superior part it includes the word STOP and below it is written the nature of the control or the reason of the required stop, which can be Police, Custom, Health, Toll, etc.
background.
The NO ENTRY sign has only white border. The background is red with a horizon*,al white bar.
ln order to
improve the legibility, only the following signs
includes transversal bar.
* No Left Turn, No Right Turn, No U Turn * No Stop, No Parking * No Use of Audible Warning Device D=85cm
Prohiblted Traffic The sign RO indicated that atttraffic is prohibited on both directions for all vehicles.
No Entry for all Vehicles This sign R3-1 indicates in the beginning of the one way road that the vehicles can only circulate in opposite direction. lt is necessary to repeat this sign on all intersections along this one way road.
340 I
]'
Prohibitive Sign FIGURE
1O-
End of Prohibitive Sign
5 MEASUREMENT OF PROHIBITIVE SIGNS
341
Traffic Engineering
Elernents of Roads and Highways
10-6 Obligation Signs
O
The meaning of the following Obligatory Direction signs
R2-l No €ntry for all Vehicbs
Prohibited Trafhc
No U Tum
@ @ No Parking
Prohibited to Cars
No StopNo Parking
@ @
No overtaking for vehicles whose weight exceeds 3.5 T
@
No left tum
Prohibited to trucks
No overtaking
- Obligation to continue straight ahead (R) - Obligation to follow the right direction R2-2 (L) Obligation to follow the left direction R2-2 R2-3 (R) - Obligation to turn the obstacle by its right side R2-3 (L) - Obligation to turn the obstacle by its left side R2-4 (R) - Obligation to turn right R2-4 (L) - Obligation to turn left R2-8 (R) - Obligation to go straight ahead or to turn right R2-8 (L) - Obligation to go straight ahead or to tum left R2-9 - Obligation to turn right or left R2-10 - Obligation to use the roundabout
No right tum
Prohibited to pedestrians
@
Prohibited to animal drawn vehicles
FIGI-.'RE
34)
10-6 PROHIB IVE SIGNS
FIGURE 10.7 OBLIGA'I'ORY DIRECTION SIGNS
343
Elements of Roads and Highways
Traffic Engineering The Obligation Signs are circular in shape. The background is dark blue. The symbols and border is white. If the istration enforces prohibition or an obligation sign, it has to inform the driver the end of this restriction to ttre highway use. For example; the No ing Zone, the No Parking Zone, the speed limit, the prohibition to use audible warning signal and others.
{-+ t-r.s
I
1-t 1gi \ !-i--_-_____
"t $q {o
FIGURE 10.9 OBLIGATORY DIRECTION SIGNS
10-7 End of Prescription Signs
n. La,/Ai iltl.,u -'. ---,
281 -ll
I l\
i
|
---f--
|
t---------.21.s -- ----__.1 FIGURE 1O€ MEASUREMENT OF OBLIGATION S|GNS
344
4
The end of all prohibition signs is also circular in shape and represents the sarne bar sign obligation symbol. A red bar from the right top to the left bottom cancels this obligation. The R4-2 informs the drivers of the end of all the previous prescriptions. However, it does not include the law that prescribes the national speed
limit. 345
Elements of Roads and Highways
Traffic Engineering
The R4 notifies the driver of the end of all particular speed limits other than those defined by the general laws, speed limits previously applied to all vehicles or only to one or several categories. The sign should not be setup on the road where tle speed limit is greater or smaller than tlle ones prescribed by the general rules. -
i:[1"''> ADVANCE DIRECTION SIGN
O
End of all indicated prohibition
BULACAN Ehd of speed iimil
End of overtaking prohibition
(R\
v
INTERSECTION DIRECTION SIGNS
End of prohibition limiting weight greater than 3.5 T
End of reserved lane for buses
End of prohibition using audible waming signal
FIGURE ,IG1O END OF PROHIBITION SIGNS
10-8 Direction Signs Direction signs are divided into four categories
l.
Advance direction sign Intersection direction sign
2. 3. Reassurance of confirmatory slgn 4. Entering and Exit of urban area
CONFIRMATORY SIGNS
TT" four categories are well defined in the philippine Road Signs Manual. In Europe, a different green is or"d- fo,
background of the sign. It is more intense with an emerard tint. ?.46
FtcuRE
r0-rr DrREcnoil stolts 347
Elements of Roads and Highways
Traffic Engineering The driver should be informed that he is entering the crty of CX) and to refrain from being attracted by anything except to look at the shop signs only to know where he is.
The sign EB10 is rectangular in shape with white background, red and white borders and dark blue letters. At ttre end of the city proper, another sign EB20 notifies the driver that he is leaving the place and that he can resume his speed under the traffic regulations. These two signs, limit ttre area where the attention of the driver is concentrated. Outside the city limit after the EB20 sign, the condition of driving will be different givtng the driver the signal to resume his speed.
Md-2
?*-
lrc
lri 2
10-9 Informative Sign The objectives of this sign is to give the driver miscellaneous information usefi.rl in his driving and general knowledge. The signs are square in shape with dark blue background, white symbols and letters bounded by white borderline. Informative signs may include red symbols and bar notifring the end of prohibitions etc. MC
MC
2
2
Material Requirements
FIGURE 1O-12 DIRECTION SIGNS STANDARD MEASUREMENTS
These green signs with white letters, bonrer and arrows are used for nafional highways. For expressways and freeways, blue background signs are used. The letter synnbols and bo.deis a.e
all white. For small rural roads, white backgrou"O black leuers, numbers and borders are used,
,ign. *iih
Entering and Exiting Urban Areas
It is necessary to advise all vehicle drivers that they are entering an urban area where the condition of traffic is diffeient. :48
Sign s for warning, regulatory and informative signs are manufachrred from aluminum sheeting of at least 3 mm in thickness. The Reflective Sheet used for road signs consist of spherical lens elements embedded in transparent plastic having smooth, flat surface with protective pre-coat adhesive which are pressure sensitive for manual application or tack free heat activated for mechanical vacuum heat application. The minimum brightress value of the reflective sheet compared to magnesium oxide should be in accordance with Table l0-2. The brightress of the reflective sheet when totally wet by rain should not be less than 90% of the given value. 349
Elements of Roads and Highways
Traflic Engineering
m
2.
tEl
,;;;"n
m Combrtrwn
End offteeway
4.
The reflective sheeting should be flexible to permit application and adhesion to moderately embossed surface. The sheeting should be solvent resistant capable of withstanding cleaning with petrol, diesel fuel, mineral spirits, turpentine or methanol. It should be weather resistant without discoloration, cracking, blistering, peeling or any dimensional changes. The sheeting must show no cracking or reduction in reflectivity after dropping a 25 mm diameter steel ball from a height of 2 meters into its surface. The adhesive should permit the reflective sheeting to adhere accurately 48 hours after application of 90"C temperature.
Picnic area
Hospital with emergenqy servi€
Ferry boat
m Priority to this direction
TABLE 1O-2 RtsFLECTIVE BRIGHTNESS OF TRAITTC SIGN SURFACE
Mnimum Rcfl cctivc Brightrrcss
Valrr comparcd with MgO 0.5" 0.50
0.5" 0.5" 0.5" 0.5" 0.5" 0.5" 0.5"
No through road
FIGURE
350
One way
Perting
1S13 VARIOUS INFORi'ATIVE SIGNS 351
Elements of Roads and Highways
Placement of Signs
Traffic Engineering
4.
The position of individual sign depends upon its purpose and circumstances peculiar to its location. If possible, iocation should be standardized. Positioning provides another set ofcues to motorists. The Manual recommended the right positions for all situations to wit:
l. 2. 3. 4. 5.
Warning, Regulatory andAdvisory signs for rural roads are mounted 1.80 to 3.60 meters from the pavement edge with the bottom of the sign 1.50 meters or more above the roadway. On high-speed roads, warning signs are posted as much as 450 meters ahead of the hazards. Rural road warning sign distance should be placed about 250 meters and75 meters in urban areas. A horizontal clearance not less than 60 centimeters be_ tween the curb face near the edge of the sign a minimum height of 2.10 meters above the curb is prescribed where vehicles may park along the curb.
Sign positioning must fall within the driver,s field of view so that drivers may not be looking away from the
5. 6. 7. 8.
they must appear in the
headlight to be effective at night.
10-10 Traffic Signals Traffic signal is defined as all power operated traffic control devices, except flashers, signs and markings for directing or
1. 2.
l. 2. 3. 352
Provide orderly movements of traffic. Increase the traffic handling capaclty of intersections. Reduce the frequency of certain types of accident.
Interrupt heavy traffic to permit crossings by other vehicles or pedestrians.
Control the traffic lane use. Provide ramp control at freeway entrances. Intemrpt traffic for emergency vehicles and at movable bridges.
Excessive delay to motorists and pedestrians.
3.
Disobedience to signal indications and other particular installations. Diversion of traffic to less advantageous and undesirable
4.
routes. Increased accident frequency like rear-end collisions and pedestrians.
Signs and directions are enforceable only if they are installed under legal authority. Model legislation is found in the Uniform Traffic Laws and Ordinances.
Traffic Signals are Classified into:
l.
warning motorist cyclist or pedestrians.
Each of these different types of signals.serves as one or more of the following functions:
speed.
The belief of la1'rnen and public officials that traffic signals could provide solution to all traffic problems, has led to the numerous unsuccessful installation of traffic signals. The unfortunate results of unplanned installations of traffic signals are:
roadway.
6. If the signs are not illuminated,
Coordinate traffrc under conditions of favorable signal spacing so that it flows nearly continuously at definite
2.
Pre-Timed Signals - where traffic time intervals are divided to the various traffrc movements.
Traffic Activated
-
where time intervals are controlled
as a whole or in part by traffrc demands.
Modern signals are electrically operated. Individual units have separate red, yellow and green lenses with 20 or 30 cm. diameter each has its own light sources. The 30 cm. lens is specilied for irtersections where 85% speed exceeds 60 km. per 353
_ i
Tralfic Engineering
Elements of Roads and FlighwaYs
hour for all arrow applications and for problem locations. Sig:' nals pedestal or brackets are mounted outside the roadway limit, sornetimes they are suspended above the intersections by cables, mast arm or other .
5.
Mounting Specifi cations
7
l. 2. 3. 4.
6. . 8.
'lhe recommended height for post-mounted signals from the bottom of the housing is 2.40 to 4.50 meters above the sidewalk or crown of pavement, if there is no side-
9.
walk. The minimum mountrng height is 1.35 meters. The minimum and maximum vertical clearance for signals suspended over ttre roadway is 4.50 and 5.75 meters
10.
respectively. For each through movement, two or more signal display of faces visible to approaching traffic is prescribed. This is to give the driver following immediately behind trucks a chance to see the signal indication as they approach the intersections.
@ @
@@ 354
Where signals must intemrpt fast moving traffic on expressways, the cornmon practice is to install three or four signal faces on each approach. Under special conditions like heavy pedestrian movement, school crossing, mid lock crossing arrd special rectangular pedestrian walk, the ..Dontt Walk" signs with either words or symbol message is extremely nscessary. For non-intersection pedestriar crossings, two signal
faces for vehicles are required augmented b1'
signs
pavement maikings and parking restrictions.
Positive Meaning of Each Color
1. The steady
2. 3.
Circular Green... Means GO Green Arrow..................,..... Go to such direction Solid Red light ... .......... Stop and wait for a green indication.
4.
Flash Red ...............,...."........M&ms an arterial Stop Sign 5. Flashing Yellow Means Proceed with caution 6. The use of Steady Yellow for caution is prohibited except as waming between green and red indication.
Location of Signals
1. A
distance of 12 to 36 meters beyond the top line for t'"ical right angle intersections far side by mast arm or cable zuspended locations.
2. If bottr signals are post mounted, install on the far side, 3.
FIGURE 1G14 TRAFFIC SIGNALS
Signals must be visible to approaching vehicles witb a distance ranging from 30 meters for an 85 percenule speed of 30 km./hr. to 21CI meters for 90 km. per hour. Where a continuous view of at least two signal faces are blocked by physical objects, warning sign is required. For an excessive t rnring lane, one slgnal face is required.
one on the right and the other on the left or median. The angle between the drivers normal sight dire,ction, either of the signal faces should not be more than 20o angle 355
-
Traflic Engineering
Elements of Roads and HighwaYs TABLE IG3 PARTTAL DATA ON RECOMMENDED ROADSIGN INSTALLATION PRACTICES* Minimum Dimension in Inches
Purpose
of Design Warning of hazard
Diamond
Triangular Black
Railroad crossing
Disk
Regulatory sign
Vertical
on
Ellack on
Yellow Yellow
36 (vert.) x 48 x 48
24 or
Rectangle
Black on White
height variable
Octagon
White on Red
Primary 30 x 30
Triangular
Red on White
sa€*
30'wide
Fis* F::*.o '5cc) ;T B e o.O
24x?A
36x36x36
Vertical
Rcd on Whitc or
Rcctanglc
Grccn on White
Parking - Rural
Vcrtical
Red on White or
Informational
Rcctangle Grcen on Whitc Horizonial Black on Whitc
Parking - Urban
E
?An
' =p E:8
x30"
Fr F.e to o9 rno Fx oo .^o
Whitc on Grcen Sccnic Rest
Route lvlarkers
"Be
spccial
3g
Shield
rt .'
Black on Whitc
8
o
o-
*= x3 >1
9x12or12xl8
35
Rcctangle
3; 5q
r Based on Manual on Uniform Traflic Control Devices
o hJt.JH-
^6< \J!t
8888 <ex l'
o
ET
5
o
tc I
F
F
Gt
o
{
F
I
tsdF
19
o
t
--l \O \O \t 8888 E:E
sgffo
F
+
t
D
o
I
E
€
Bg.
(D
a^.-I-l
5 5 u,ut
3 o
vv zrl z
o rl
7 !t !
o 2
vr
z
or
to
lg .?Ye e
9a Yd ,o
t,
-l t
357
r
o o
c
9a
=. ;E
3 3 t!
!.,5
o
356
g
v)
<s; oo =ro C)X'
Black on Orange
Vcrtical
3
5F
White on Red
Maintenancc Pedcstrian Control
F
F
lll
z
'u
F o
ut
IE
E
ld IP gs< t{ le .$
8888 I pq 8"S
:'O and Bluc
Construction and
(/t O\ O\ Ll
5r 6'
t-;i!
-
eg tatr
Tnpczoidal White on Brown Shicld or Black on Whitc
Road Markers
interstate
a7
tl
g eB O r{
"< H3
E*
Horizontol White on Grccn Rcctanglc
Recreational
B' li.
EE.F
Rectangl., White on Black or
8Es E +r
O
='6
Rcd bordcr
9? q
N)f.J-F.
rF53 rl
$'< E
I
6Fl1rX
C *\t g6O-'
sq
O
fgsx-g
36n diameter
Secondary
Yield
Y.O O -'-ot
z?7
FE
I
t
;'€ { F d'; E"E sg;E
e?
I 9q I 33 | ao ae
-t:ts'.
o
30x30
Black on Ycllow
No ing zone
Stop sign
g 5 ()
Traffic Engineering
Elements of Roads and trIighwaYs
4.
'l"he Uniform Vehicle Code prohibits illuminated advertising signs that interfere with the effectiveness of traffic control devices. The Manual recommended that local government legal authority should prohibit them.
Signal Control
A solid-state mini-processor for intersections control must be available. The mini-processor receives inputs from detectors, and interprets their meaning, then select the appropriate set of signals from those in the processor's memory bank These devices can accept thousands of instructions per second and respond very quickly to any changes in the traffic. The advance miniaturization systems make it possible to combine the advantages of pre-timing coordinated movement and tlaffic acluation in a single or area wide intersections to reduce cost and delay. Today, most detectors consists of wire loops installed under the road surf;ace that the presence of vehicles through changes in their magnetic fields. A more sensitive series of loops recording the number of vehicles waiting to m:,k-e a maneuver. Transverse and loops are sometimes installed diagonally in part to detect the presence of motorcyDeg an effective detector system is not easy because the location of detector loops in relation with the stop line depends on the traffic control plan. The detector is somstimes placed at a distance from the intersection where vehicles on the main road are approaching at high speed and expectrng to continue through. Another close-in detector is installed to prevent entrapment at the stop line or to extend the green signal time. The distance where detectors are installed ranges from 55 meters for 45 kmftr. to 135 meters for 90 kmihr. speed.
6.
road, pedestrian needs, zurd vehicle speed approach. Thc Traffic Manual recornrnended that dre total time allowed for pedestrians should be an initial interval of 4 to 7 seconds to start plus walking time computed at 1.20 meters per second" On wide streets, pedestrians rnay be stopped on medians at least 1.80 meters wide. However, a separate pedestrian signal activator must be installed on this median if pedes-
trian push button is incorporated in the overall control system.
Ordinarily, the time required fbr cornplr:te sequence
Under normal traffic volume, coordinated signals at various intervals estimated from 750 meters to more than a kilometer is effective in making smooth flow of traffic. On the contrary, when the street is loaded to capacity, coordination of signals is ineffective in making smooth traffic flow.
The four systems of coordination are:
l.
Cycle Length of Signals
358
5"
Synchronized Movement
cles.
l.
indications fall betrveur 30 and 120 seconds. To reduce delay of strnding vehicles, short cycle lengths are adopted. Holever, a relatively high percentage of the total time is consurned in clearing the intersections and starting each succeeding rnovements. 2. A larger cycle increases the percentage of time lost. For high volurne traffic it is necessary to increase the cycle length to gain additional road capacity. 3. Approximately, one vehicle can each traffic lane with normal signalized section in 2 second of green light. 4. The yellow inten'al following the green signal is usually between 3 to 6 seconds depending upon the width of the
of
Simultaneous coordination
2. Altemative coordination 3. Limited progressive 4. Flexibleprogressive
359
Elements of Roads and Flighways
Simultaneous coordination makes
all color
Traffic Engineering indications
along the street alike at the same time. It produces high vehicle spoed between stops but have low overall speed.
ln Alternative Coordination, all signal changes their indication at the same time, but adjacent signals along the street show different colors. This is fairly well on a single street that has approximately equal block spacing. [t is also efFective in controlling traffic in business areas several blocks on one side trut only when the block lengths are approximatd equal in both directions.
The Limited Progressive System retains a common cycle length providing separate "GO" at each uttersection to motor traffrc progression. This gives continuous or nearly continuous flow of vehicle group at designated speed in one direction and discourages speeding between signals.
The Flexible Progressive System is provided with a master control that commands the controller for the individual siguals. The systerns give proper coordination between signals and make prcdetermined changes in cycle length, cycle split, and offsets at intervals during the day For example, the cycle lenglh of the entire system could be lengthened during peak hours to increase the road capaclty and shortening other time to decrease delays.
10-1
I
Pavement Markings
The early road marking was first introduced in Wayne Country of Michigan in the year 1911. After a decade, pavement markings gained universal acceptance.
Pavement marking was introduced to delineate 1. Roadway centerline 2. Lneboundaries
4. Pavement edges 3. No ing zole 5. Roadwaytrar:sitions 6. Tumingpatterns 16()
7. Approach to obstruction 8 Light rail or bus clearance 9. Stop line 10. Cross walks 11. Railr
To be respected, pavement marking should be simple, easy to understand, well designed and properly located. tn ttre prrii, ippines, 80% of the drivers do not respect the horizontal mark_ ings because it is too complicated. For example:
l. 2. 3. 4.
The continuous white line Simple continuous yellow line Double continuous yellow line
Broken white line bordered by two continuous yellow lane
What is the barrier line? The 1968 Vienna Convention gave the answer: A continuous line must not be crossed. It ii an imable wall All other broken lanes can be crossed with or without care
Specific Use of Colors
a) White is used where vehicles may cross the markings like
l. 2. 3. 4.
Lane lines Pavement edge lines
Channeling lines Turn markings
5. Stop lines 6. Cross walk 7. Parking space limit line 8. Words and svmbols
b) Yellow Lines delineates the separation oftraffic flows like
l. Center line oftwo highways. 2. Double centerline for multi-lane roadway. 3. No ing barriers or zones of two and three lane road 4.
and road transitions. Channeling a c€rrter lane
5.
vided multi-lane highways. Obstructions must be ed to the right.
for two-way, left turns on undi_
361
Traffic Engineering
Elements of Roads and Highwavs
c)
Dashed Lines for directional line such as center strips on two lane highways and lane lines. The ratio of the stripe to gap is I to 2 stripes - 3 meters long and 9 meters gap is recomrnended for rural roads. Excessive use of continuous lines should be avoided when it leads to the creation of artificial traffic bottlenecks or to a noticeable decrease ofthe capacrqy on an important length of road. The Rules State that:
l. A
contirurous line shorild not be placed in sections where the visibility is greater than the minimum lengfh
2 3.
for ing. There should be no continuous line in the sections w'here small width of travel way hinders the drivers to respect the continuous lane.
'[he length of contimrous line is strictly limited to the indispensable length. The minimum length is: 30 meters rn rural area and 20 rneters in urban areas.
The beginning of a continuous line must be designed not to surprise the driver. Drivers must understand the reason of the continuous line. For instance, the long straight line along a wide
bridge on flat area where the driver cannot understand the purpose of such continuous line. The driver will not respect instructions that he does not understand. Nexl time when the continuous line is necessary, the driver will ignore the waming and cross the line thinking once again that this line is only a landscape for beautifi cation. For urban areas, short length may be appropriate. On the contrary, yellow barrier lines and white guidelines are generally continuous on where crossing is to be discouraged. The recommended stripe width is 10 to 15 centimeters, and for emphasis, a stripe double the usual width is recommended.
Requirements for Ideal Road Markings
l. ?62
It must be cheaper to install
2. 3. 4. 5.
Should be permanent
Must be readily visible day and mght, rain or snow. Even with water standing on the pavement, the surface markings should clearly transmit to the motorist the intended message.
Marking should not be destroyed by snow or dirtremoving equipment.
The Paint Materials for Striping
l. 2. 3. 4. 5. 6.
Modified alkyd resin with Titanium Dioxide (white) or Lead Chromate (yellow) pigment. The paint film thickness should be in a range of 0.015 inch with about 60% solid. The paint coverage should be about one gallon per 100 meters of continuous i0 centimeters stripe. In addition, 2 tD 3 kilos of glass treads with an average diameter of 0.5 rnm per gallon is added to the paint or
by drop-in during application. Re-striping (re-painting) frequently depends on a variety of factors reported to be as frequent as 3 times per year where traffic is heavy. Paint must dry after application at the rate of less than 60 seconds and not more than 3 minutes.
Other Markings:
A raised reflector less than I rnch in height illuminated by vehicle headlight is widely used. White color is used for lane marking, bhre color to outline bicycle lanes and red to fucrng vehicles traveling in wrong direction to the freeway entrances or exil rnmps. The raised reflector creates rumbles on running vehicles when it crosses the line or tray on it. These devices are mounted on the road by means of epoxy. The disk or reflector serves to alert inattentive drivers. The large mushroom button type was one time employed as pavement markings but their use are found to be objectionable. 363
Elements of Roads and Highways
Traffic Engineering TABLE lOS COMPOSITION OtrPAVEMENT PAINT SOLVENT
I
,if rli
Raw Tung oil Normal Butyl Alcohol Aoctone (dimcthyl Ketone) Dcnatursd Alcohol (Formula No.
I
t (o
l)
15
o/o
l7
o/o
34
o/o
34%
Thc alcohol and acctonc are mixcd first thcn thc oil is addcd to form a clccr
,f
solutionat2loC.
I
l.r ,f i,,l E I 1
i I
I
I g
I T, ill :! l,l TJ ,ii
r +'
TABLE
EEE ililll :J5
I
---tI I I
q o
R
I
Ess.c i':'t
I
..j
I
I
I
rgg !P!.g
E.g,.c, I :lI
Titanium dioxidc (anatasc ) Mcdium Chromc Ycllow Para Toncr ( liSht ) Extondcr
TABLE lOE COMPOSITION OF?NNT
co T .C
i I
Compositionby Weight %
: ;o
E
I
I il ,ill "i ll _l
TABLE I(}7 COMPOSITION OFPAINT PIGMENT
tr.c
I
I
ES€ KEE
988 Qn v
i I
(!
a
ITT I
I
I
r-i-r-l-ri-t
I
8
I
I
COMPOSITION OFPAINT VEHICLE
p88
I
_il
II}6
l
Compositionby Weight%
co
J
Pigmcnt
Vchiclc
4245Yo 5*58c/o
23o/o
77
o/o
NNOoa
l. Para toncr to standard shadc 2. orrc part by volumc and I acctatc is addcd to lfi) parts paint 3. Sultcient Prussian bluc is addod to thc raw tug oil for thc whitc paint FIGURE
354
1Gl5
BROKEN LINE TYPICAL MODUI.ATION
to ovcrcomc its vcllowish tint.
365
Traffic Engineering
Elements of Roads and Highways
Words, I-etters or zurows are also placed on the pavement to notify the motorists that they are approaching hazard zone Such as railroads, school crossing, or to mark straight through or turning lanes. Symbols, words or numbers convey information such as Speed Limit and the nearness of schools, hospitals, judiciary courts, etc. Pavement markings have been proven effective in the reduction of accident, and much is yet to be learned ofdriver's response.
Paint should not be applied on wet pavement and during damp weather, or when the air is rnisty. Application is preferably by machine but where brush is used, only round or oval shape not exceeding 10 centimeters width is permitted.
Ballotini for Reflective Road Paint
For punctual obstacle like the curb of bridge sidewalks shall marked be by one or several reflectorized dwice. The color is red if the obstacles are on the right side, white or yellow if they
Ballotini consists of beads of good quality, optically clean, lead free glass with not less than 90Yo spherical and free from flaws. The beads contain not more than one half percent of foreign matter free from flowing under normal atmospheric condi-
Traffic paint is applied producing a uniform even coating in close with the surface being painted. It is applied to the pavement at the rate of 0.33 liter per square meter and dried sufficiently and free from cracking from 15 to 30 minutes.
are on the left side.
Reflective Pavement Stud
tions. TABLE IG9 GRAI'ING OF BALLOTIM US Standard Sieve
mm
Inch.
Percentage ing
by Weight
l.l8
No. 16
100
0.85 0.60 0.30 0.18
No.20 No.30 No.50 No.80
65-75 45-55
t2-25 0
For proper light reflection, the proportio.n of ballotini to paint should not be less than 45 kg. per liter and not more than .50 kg per liter of mixed paint. In cities with street lighting the use of reflectorized paint is not necessary. Thermoplastic materials with or without reflective properties can be used in locations subject to extreme traffic wear. The service life of this material is five times that of beaded trafhc paints.
3(6
Reflective stud is either Flush Surface or Raised Profile type with the fol lowing characteristics :
L
The Flush Surface R.eflector short base type measure 120 mm x 140 mm. The base is formed on cast iron with adequate webbing to insure a firm key to the road when installed. 2. The pad is highly resilient and durable rubber reinforced with canvass des:gned for at least 5 years. 3. It is designed to produce a self-wiping action of the reflectors when depressed. 4. The reflector is made of impact and abrasion resisting glass hermetically sealed into a copper socket. 5.
6.
The Raised Profile Reflector consist of acrylic plastic and shell filled with an epoxy compound molded from methylmethacyclate into the shape of a shallow frustum of a pyramid with base dimensions approximately 100 x 100 mm and thickness not more than 20 mm. The shell contain two prismatic reflectors, each inclined at an angle of30o to the horizontal and having an area of not less than 20 cm2. 367
Elements 7.
of
Traffic Engineering
Roads and Highways
The Reflectors minimum specific intensity values expressed as candle power per foot candle of illumination at the reflector on a plane perpendicular to the incident light givur in Table l0-2.
8.
Cement Mortar shall consist of one part portland cement to two parts fine aggregates mixed wrth water.
Advance Marking
Each reflector for testing is located at the center of the reflecting face at a distance of 1.50 meters from a uniformly bright light source having an effective diameter of 5 mm. The width of the photocell is 1.2 mm shielded from stray light. The distance from the center of the light source and photocell is 5 mm. Failure of the reflective faces more than 4% could be a cause for reiection of the complete batch. TABLE IO.TO RAISEI' PRONLE PAVEMENT STUDS PHOTOMETRIC PR.OPERTIES
Divcrgence Anglc Incidcncc Angle 00 200
0.2"
.oo-_=-
1.O0
0.75 0.30 SELECTIONARROW
The reflector shall a vertical load of 1000 kg (kN) when tested in the following manner:
l. 2.
The reflector is centered horizontally over ttre open-end to a vertically positioned hollow metal cylinder, 75 mm internal diameter 25 mm high and 6 mm wall thickness The load is applied to the top of the reflector tluough a 6 mm diameter by a 6 mm high metal plug centered on top of the reflector. Failure shall constitute either breakage or significant deformation of the marker at any load less than 1000 kg. per foot.
Adhesive. When Raised Profile type reflector is specified an approved epoxy adhesive is used. 368
so -
.os
;24
HQhway or lane axis
R=21
1.12
__
a.g) _
f- .r,1.lss--l ----1 l--
6.O0
I
FIGURE .IO-16 RETURN TO LANE ARROW
369
Elements of Roads and Highways
Traffic Engineering
\
.:os
,\
\\^Tl*'
I arr
r3r
l|f|l||trt ttartr al ttsarttrY rtll
l_
r.---:r '
-l - ,. -a -L.. -<-!F:_-11.3v__ 6
?
FIGURE tO-17 TAPER tetARKtNGs
r
t
_
FIGURE lO-18 DtVtSlOfttAL tSLAlitD Ot{ SECOIDARY ROAD
370 371
Traffrc Engineering
Elements of Roads and Highways On two-lane highways, all continuous lines are preceded by warning broken lines. The line must be completed by Return to Lane arrows. At the approach of the continuous line and in the case of reducing the number of lanes, the use of Return to Lane Arrows is compulsory to incite the driver to use the indicated lanes.
lfre arrow overlaps the warning line. On multi-lane highway, the arrows are sst out on the axis of the lane to be suppressed generally by the left lane in the considered direction. The number of arrow is normally three. In urban area it can be reduced to two. On certain exceptional cases like sinuous roads, the number could be increased to 5. The advance selection warning and the identified position can be on selective cases in urban areas by painting an Eurow on the pavement called selection arrows asg each lane to one or several directions. The use of these arrows is to limitthe left tum and right turn specialized lane.
There are Six Types of Guideposts or Bescons.
l. Curve guide post 2. Intersection guide post 3. Hazard marker 4" Nose Marker 5. Delineator 6. Wind cone Ref,
Jl J3 14 J5
J6
J7
€crtorized red materials
(t
N _t
o o I I
10-12 Guidepost and Markings Guideposts are set to guide the drivers and to pinpoint a particular or linear danger.
CIRCUI.AR SECTION
SQUARE SECTION
FIGURE 1O-20 SECTION OF CURVE GUIDE POST J1
zs ,/ .----.| 20
--t I
130
I
80 I
CIRCULAR SECTION
FIGURE 1O-19 CURVE GUIDE POST J1
372
I
SQUARE SECTION
FIGURE 1O-21 INTERSETION GUIDE POST J3
-1
/-t
Elements of Roads and llighways
Traffrc Engineering
Non- rcllective dark Hue
l. bI o o\ Nt J o-'
---l I I I I
E
Ref,eclive white
o @
FIGURE 1O,22 HMARD MARKER J4
,"""",""r1
Shoulder Non refiective dark btue
Reflective white 30"
--<'
.
F-f:
FIGURE 10-23 NOSE MARKER J5
I
11
Delineators Delineators are light reflecting devico mounted on posts at the side of the roadway in series to guide the driver along the proper alignment.
FIGURE 10.24 DELINEATOR POST J6
4.
least on one side of the ramps.
Specifications:
1.
2. 3. 374
ln straight alignment, tlre spacing betwoen delineators is 30 msters and the same interval is observed in curve with 300 msters radius or more. For smaller curve; 20 m. spacing with radius between 150 and 300 meters, l0 m. spacing on curve with a radius less than 150 meters. Under normal atmospheric condition, it shall be visible at a distance of 300 m. under the upper headlight beam.
Delineators are specified on the right side of expressway and freeways unless these are fixed lighting and at
For edge lines the color must be the same. Red reflectors may be installed on the backside of ramp delineators to tell the driver that he is going the wrong way. 6. It is recommended that they should be used on two-lane two-way road. The recommended spacing is between 50 to 150 meters or tangents. 7 It must be progressively smaller on approaches to curves with minimum spacing from 6 meters with 15 meters radius to 30 meters with 300 meters radius. 5.
375
Elements of Roads and llighways
8. 9.
Traf,fic Engineering
Single delineators may be installed on the left side q'here the road is curving to the right.
On freeways, two yellow delineators at 30 meters on center is specified along acceleration lanes. Roadway narrowing should be marked for their full length. 10. Where curbs projects into the travel way, their ends shall have yellow reflectors if traffic moves to the right, white if it is to on either side.
Whatever type is used, delineator is called single face if it has one reflectorized device and double face if it has two devices. The single face is used on one direction travel rvay and the double face on two directional highway.
rng the distance from the crty of Rome to other principal cities were ftrund. Today, kilometric markers were insialled to assist the rnotorists in estimating:
l. 2. 3.
Travelprogress Pinpointing accident locations Distinguishing the positions of structures such as bridee
4. 5.
To identify road sections for cost ing purposes. To designate where maintenance is to be done.
and culverts
Raised bars are sometimes called "Jiggle Bars" used as charurel device at the nose of traffic island to keep vehicles out of certain paved areas. They are lower than the curb made of concrete or asphalt painted or reflectorized sometimes set diagonally to the vehicle way oriented to direct it back on to the right course.
Rumble Strips Rumble strips'are installed across the roadways to alert the motorist as they approach a dangerous situation like stop signs or abrupt changes in the oncoming alignment, grade or profile. Rumble strips are specially designed to create roar in the running vehicles.
Distance Marker
At the side of the roadway, kilometric markers are installed at every 1000 meters distance. These markers are usually made of reinforced concrete indicating the number of kilometer disumce from and to a specific place. The origin"of this marker was traced to have started as early as the Roman tirnes. Early markers were large upright cylindrical stone monuments show-
FIGURE 1O-25 DISTANCE MARKER
10-13 Griardrail Guardrail is generally designed to prevent a car from leav_ or from colliding against an obstacle by deflecting it so that it continues to move at reduced velocity along the guardrail and in tle normal direction. Guardrail is disigned to stop vehicles whose weight is smaller then lg00 kg. The need for guardrails on fill is related to the slope and height of the embankment In the Philippines, guardrails are not properly set and they may constitnrte additional road hazards than safetv dences. For instance: rng the highway
376 3'17
Elements of Roads and HighwaYs
Traffic Engineering
of the guardrail sections are not equipped with proper protection thereby constituting a kind of sword or battering ram which can penetrate inside t}e car during an impact. Sometimes the rails are mounted too high becoming seriously hazardous that could enter into the vehicle and The beginning
End of section
2.
decapitate the car occupant. 3.
4 holes 2.7 x 3.75
The superimposition of the different elements of the guardrails is done in the \ryrong direction. During an impact, the element can be flaked off endangering the motorists.
Elemcnt lenglh
Eeginning of section
E
43.10
End
of lcctiong
holes 2.3 x 2.8
Other Setup Arrangements Making the Guardrail Absolutely Useless
1. 2. ELEVATION
3.
Hole 17 x 50 Bolt 1.6 x 4.0 TH
Bolt 1.6x4.0TH
Oval
hole2x6.3
lr ll
8.2
L
6olt # 16 8 holes 2.3 x 2.8
Pcst
C
25x 50 x
100 x
5.
182
50x25 x'i
6.
Guardrails were fixed on the post transmitting directly the energy of impact to the that cannot sustain the shock. When the barrier collapses, the vehicle es over easily.
The holes and bolts used were not in accordance with the design and specifications. The s are sometimes located very near the crest of the slope. The foundation is weak to prevent the post from being tipped offduring an impact. Guardrails are frequently used to protect the structures, direction boards and traffic signs but not the drivers. Guardrail is used perpendicular to the flow of trafEc in the shoulder or in the median to protect a manhole. In case of impact, the economic cost of car damages will be greater than the cost of ths manhole repair. Guardrail is often used to replace the J4 marker or barrier.
t0-14 Concrete Barrier
OVERTAPPING DETAIL
FIGURE 10-26 GUARDRAIL TECHNICAL DISCRIPTION
378
The concrete barrier was introduced in the USA. n 1972 under the following conditions:
It
was
tested in
379
Traffic Engineering
Elernents of Roads and Highways
l. 2.
For light vehicles the impact angle of 30 degrees at a speed of 80 kn/hr" For 10 tons truck with impact angle of 20 degrees at 70 kmlu.
After two years of testing in real conditions, this tlpe of Separator was authorized rn the entire road network of . In 1977 it was used in USA, Canada, Sweden, Belgium, Germztrly, Ivory Coast and Morocco. Record shows that no cal or truck has ever crossed this kind of seoarator or trarrier.
Functions: The concrete separator is a rigid retaining device. It does not absorb kinetic energy by its own deformations:
a) For light vehicle weighing less than 1800 kg it's function is dependent on the angle of impact. If this angle is small, the section of the separator acts on the tires to guide back the vehicle to the travel way without serious damage. On the other hand, if the impact angle increases, more damages will be visible. The impact energy is absorbed by friction and deformations of the car body.
b) For heavy vehicles werghing 12 tons or less, in case of impact, the inertia and adherence to the ground of the separator will prevent the crossing by guiding back the truck to the right trajectory. c) For heavy vehicles weighing more than 12 tons, the separator functions effectively if the impact conditions are not very hard ( low speed, small angle.) If the separator is constructed on top of an embankment, the distance between the front face of the separator and the begin-
concrete bed if reouired Concrete bed if reauired
ning of the rounding should be equal or greater than the width of the separator itself. It is necessary to design a supplementary anchorage, concrete bed or a reinforced foundation beam. 1 m. min
FIGURE 1O-27 CONCRETE SEPARA'TORS
The separator can ensure double functions: as guardrail and as barrier. The double concrete separator was designed to be set-up on medians or shoulders. The single type has a reduced section and its use is limited to particular cases. The concrete separator being solid and rigid device camot differential settlements. Thus it must be set up on stabilized ground in order to eliminate the risk of rupture.
r80
FIGURE 10.28 LOCATION OF SEPARATOR4 ON MEDIAN
381
Traffic Engineering
Elements of Roads and Highways When the wall is set on the centerline the width Lensth Median is: the
of
L=0.60m+2d
for longer trips. In fact, these arterial roads are existing highway of considerable length wherein cross traffic is regulated by signals and stop signs. These arterials provide access to adjacent property with restricted entry and exit locations, street parking, cross center left turn and other difficult traffic activities.
Two separators can be designed to reserve place for planting.
L > (2 x 0.48) + 2d + e for the single separator L > (2 x 0.60) + 2d + e for double separator e ='the width of the planting area. 0 .32
traffrc volume exceeds 20,000 vehicles per day.
Basic considerations in planning arterial roads
l.
0.20
Selection ofconvenient route
2. Studies oftraffic volume 3. Origin and destinations 4. Accident experienced
15
3 continuous round bars High adherence steel 12 mm dia.
Arterial Streets are considered substitute for a controlled access when
15 15
Planning Criteria
l.
Arterial road should be at least 15 meters wide.
2. Must carry at least one lane of traffic in each direction. 3. It should be at least one kilometer in length. 4. It must skirt the neighborhood areas and not just penetrate them. Possible concrete bed
5. It should be spaced about 6.
FIGURE 1O-29 CONCRETE HEAVY BARRIER DOUBLE FACE
10-15 Highway and Urban Street Operations Prior to the existence of Freeways and Expressways, Arterial streets were the main way of trafific. Arterial and local street operations make use of street marking signs and signals controlled in several ways by either fixed setting or computerized system. Despite the existence of freeways and highways, arterial roads serves the major traffrc flow to the nearest access points because arterial roads offer the most advantageous route
382
600 to 900 meters apart from
grid type street pattern. The minimum volume to justi$ arterial road is 300 vehicles per average hour during the day and 450 vehicles per hour during peak periods.
There are times when the traffic volume exceeds the capacrty of the arterial road of conventional two way street during peak hour and to unload and increase the capacity of the road, the followin g solutions are employed:
1. 2.
Parking is strictly prohibited during peak hour on one or both sides of the street. No parking is allowed several meters away on each side of intersections. 383
Traffic Engineering
Elements of Roads and l{ighways
3.
Allowing right turns on red signal or providing special
4. 5.
provisions for these turns outside through the lanes. Eliminating left turn at congested intersections. Reversing the flow of traffic in the center lanes to accommodate more lanes in the direction of heavier flow.
One Way Street One-way streets are those where traffic moves in one direction only. Making one-way traffic is based on the number of important advantages over the two way operation such as:
l. 2. 3.
Bigger Capacity. More vehicles are accommodated by the same street system. Fewer Stops and Increasing Speed. Fewer delay at intersections because the number of possible conflicts were substantially reduced. Improvised Pedestrian Movement. One crosswalk is totally free from turning vehicles durmg each phase of the signal at signal-controlled intersections of two onewav streets.
4. 5.
Ihe idea of making a street one-way to traffrc have meet oppositions from the business group and others who fear adverse effect on their interests. For instance, the travel distance to reach a certain location is often increased, a condition that seriously affect a particular business. There were inslances when due to strong objections the plan to convert the street into one-way traffic was aborted forcing the crty officials to give in after public hearing. The one-way preference streets in pairs could be an altemative.
10-16
way )
one-way two-way
One street One street (11 conflicts)
Both streets one-way ( 6 conflicts)
FIGURE ,I0.29 CONFLICT BETWEEN VEHICLES IN INTERSECTION OF TWO LANE STREETS; 2-WAY AGAINST ONE WAY OPERATION
384
Traffic Control
The most important traffrc control device for street operations are the STOP and YIELD signs and the Traffic Srgnals. The Manual calls for Two Way Stop on the less important two intersecting street where reliance on the right way, high speeds' or restricted sight distance indicates high accident hazard. The manual further states that multi-way (4-way) stop slgn installations should be used only where volumes on the intersection roads are approximatel;' equal' and only when any one of the following conditions warrants or qualification is met.
l. 2. Both streets two ( 24 conflicts
Reduced Accidents. When conflicts are elirninatecl' one-way operation reduces accidents of all types' Elimination of Headlight Glare. Ease of movement for emergency and less attention to traffic-
3.
As an interim rneasure when traffic signals are needed. When an accident problem ( as demonstrated by fve or more accidents in a year) can be corrected by multiway stop signs. When the total vehicular volume of 500 per hour enters the intersection in 8 hours or when an average dailv combined vehicular and pedestrian volume of 200 per hour from the minor highway I'rith an average delay of 30 seconds to minor streets.
Sometimes there are request from the public and its local
-?
85
Elements of Roads and Highways
officials to install stop signs where the condition does not warrant its placement. Example: a four way stop sign installed have been used where they could not be justified economically or on records ofaccident.
The Yield Sign could be a compromise between the full stop and no control. The Traffic Manual recommended its use under the following conditions:
l. 2. 3. 4.
That its bene{it include decrease
The Manual also provides minimum warrants for traffic sisnal installations based on:
l. 2.
Vehicular or pedestrian volumes. Accident experience.
3^
Progressive movement. Intemrption of continuous traffic to permit cross traffic to move as part of the network.
4.
Traffic Engineering Recommended Relief to Alleviate Congestions:
1. 2. 3. 4.
10-17 Freeway and Expressway Operafions Freeways are designed for high speed, free flowing, low accident facilities and operate without hindrances from traffic
control. This type of roadway operates well because of their isolation from the surroundings with widely spaced access and barred pedestrians. However, because of its isolation. correction is difficult if congestion develops to the frustration of the motorists who have no information as to its cause and duration. Indeed, because of its isolation, it is difficult to call for and render assistance in case ofaccidents or vehicular breakdown. 386
noticed. It is better to delay the few motorists who wish to enter the ramp than those motorists traveling on the freeway. A sirnple soluticn to congestion on the ramp is to close the ramp completely before the flow on the freeway reaches critical level. That is, if the rate of flow reaches
a pre-determined level or by closing the ramp dunng
5.
peak periods.
The use of service roads or arterial streets parallel to freeways during peak hours would gain road capacity.
Motorist Problems on Freeways and Expressways
l.
Public pressure that forces the installation of stop signs and unrealistically low speed limit signs sometimes contributed to the increased number of accidents.
flhe most common cause of traffic breakdown is adding more vehicles on the ramp. Thus, ramp control is necessary to prevent the flow disruption. Entry erf vehicles on the ramp should be restricted or stopped when breakdown on the flow of the fieeway is
The motorists are completely isolated from the surrounding community. The ramps that they could exit are far spaced, and sometimes several kilometers apart: in rural areas, and toll facilities are separated in kilometers or more in urban districts.
2. Walking on freeway shoulders is very dangerous. 3. It is almost impossible to walk on elevated structures 4. 5.
that have neither shoulders nor walkways. Motorist would not like to leave their vehicles for fear of robbery and attack. Modem vehicles are now complex and diverse in design that repairs by the driver or ing motorists is
difficult.
Solution:
1. 2"
Highway patrol should provide systematic surveillance. Emergency radio or telephone installed at roadside. 381
Elements of Iloads and flighways Emergency vehicles and crews should standby on call
to remove obstructing vehicles as quickly as possible. The agencies concerned should detail patrol cars along the fieeways for immediate assistance to motorists
-Traf'fic Engineering
5. (;.
l0-18 Street Lighting With the exception of nraior dor,inlown afieries. itighr,,'ay amd strect lighting are generaiiy incoqrorated in tli,,: rJcsrgn tt: illuullnat* the roadway tc., provide seeing by silhonefle. When an obji:ct is seen darker than the background, discermrent is by silhouette.
On the other-hand,
if
the object is lighter than its back-
ground" seeing is a reverse silhouette" A person or object on an iiluminated roadway is viewed in silhouette because the obiect is darker than the surrounding background.
neis and underes.
Lighting Source
asrsl
tri!ntallation
Highrvay iighting adopf fhe new and more economical types high and low pressure serlium and rnetallic halide but the trend is torvard the use cf high i)ressure sodium with common wattage for ali l:ypes fiom 175 to 1000 watts^
Lum.in:rires as Street Lights has the Following Criteria
1.
Recummended practice: Instali luminaires at 12.00 meters or mor{: above the roadway, although at present, the predonr.nanf mounting height is between 7.50 and
2.
When mounting
The AASHTO publication on Informational Guide for Roadway Lighting, NCHRP report 152 recommended an average horizontal illumination level of 0.6 to 0.8 foot-candle when the light source is at its lowest output due to age or dirt. It means that the light or bulb is about 1.0 foot-candle at the time of installation.
[*"or fr*eways, the uniformity ratio is set at 3:l or 4:1. 'l-he unjftrrmitv ratio is the average illumination divided b-v the lolvest illumination. The Guide also recommended the right illumination level firr lorv mounted bridge, railings and walls of tun-
3.
10.50 rneters.
is high, a rnore uniform illumination
can be maintained even though units are widely spaced.
High mounting of lights reduces the blinding effects of glare.
The guide also recommended adaptation of lighting on the leaving end of continuously lighted freeway to provide for an eye adjustment to headlight illumination. The recommended lerrel of illumination for streets and hishwavs are based on the level of lamp output.
l. 2. 3. 4.
For expressrvays, the standard proposed foot-candle is 10. On residential 1.4 fc in intermediate and 2.0 in
L
5. 6.
downtown areas.
For sidewalks on commercial areas, the recommended level of illumination is 1.0 foot-candle. For residential streets the value is 0.4 foot-candle.
7.
The requirements for collector road facilities fall be-
8.
tween those for arterials and minor streets. 388
4.
Lurninaires distribute light to a definite pattern that suits particular conditions. For a higher mounting, the spacing could be in the range of 60 meters apart with fixtures mounted on both sides of the road. Unifonn distribution could be adopted at intersections. A symmetrical pattern is used when the fixture is rnounted at the center of the street or an asymmetrical fonn when mounting is near the curb. 'llhc normal practice is to suspend the luminaires over t}te roadway, sometimes on cables or mast arms extending outward from the roadside. For roadway interchanges, the trend is to mount the luminaires on high poles, as high as 45 rneters. I
t11l
Traffic Engineering
Elements of Roads and Highways
10-20 Highway Capacity and Level of Service
10-19 Street Parking l
'Parking on the street substantially reduces the capacity of the road. It creates congestions and confusions. It increases travel time and accidents of vehicles. Legally, the right of the goverffnent to regulate the parking of vehicles on the street was established when Lord Ellenborough a famous jurist of England irr 1805 assertedthat:
"The King's Highway should not be used as stable yard" He established the principle that: "Streets are primarilyfor the free age of the public and {;nything: that impedes that age, except tn an emergency is a nuisance that may be abated. "Parhng of vahicles even infront of one's owned praperty is classtfe,l as u privilege subject to control and not as a right."
The authority to regulate parking stems fiom the police power the right of the govemment to legislate in order to protect health, safety and morals. Under such principle, public officials are free within reasonable limits to establish rules to control parking on street and to set penalties against violators. TABLE TO.II HIGTNYAY CAPACITY Facility
Capacity in enger Car
The capacity of any element of the highway system is the maximurn number of vehicles wilh reasonable expectation o1' ing over tho section (either one or both directions) during a given time period under prevailing roadway and traffic conditions. Example of capacities for modem highway element is presented in Table l0-l l.
Defining Associated With Capacity Maximum Volume. Whcre traffic flow is likely to continue without breakdown and serious compositions. It follows that at capacity, the quality of level of service is far from ideal. Number of Vehicles. Capacity is stated in enger cars per hour. Trucks and buses in the traffio stream can decrease the road capacity substantially. Reasonable f,)xpectations. Values for capacity cannot be determined exactly due to the many variable that affect traffic flows, particularly at high volumes. Assigned values for capacrty are more of probabilrty rather than certainties.
One Direction Against Two Directions. Traffic is one direction flows independently from that of the other. On the other hand, on two and three lane roads there are interactions between traffrc in the two directions and these affect traffic flow and capaclty.
A
Freeway and Expressway away from rams and weaving sections, per lane per hour.....................
2,000
Two lane highways, toral in both directions per hour...
2,000
Three lane highways, total in each direction per hour..
2,000
Given Time Period. Traffic volume and capacity are stated in vehicles per hour but traffic flow does not vary unifo.rnly with time, volume and capacities. This variation within an how is expressed by a peak hour factor (PFm) This factor which is less or equal to one in the quotient of the hourly volume divided by the shorter period volume multiplied by the
1,800
Exomple:
A 3.60 m. lane at signalized intersections per hour of green signal time ( no interference and ideal...... progrcssion)
Source: The Manual, TRB circular 212
JYU
number of periods in an hour.
lf
the hourly volume is 1,000 and the highest 5 minutes volume is 100, the peak hour factor (PFf) will be:
l9l
Iraffic Engineering Blements of Roarls and Highways
1000
x
The ideal conditions for the roadway to have an uninter12 periods in one hour at 5 min./period
100
lQ =
l. 2. 3. 4.
0.85
t2
where:
60
min :
rupted flow must:
12
5 min
Prevailing Roadway and Traffic Conditions This includes physical features that affect capacity like lane and shoulder width, siglrt distance and grades. It also reflects changes in the character of the traffic stream.
Ambient Condition is weather relateo conditions that affect
If these conditions are not met, road capaclty may be reduced. Enumerated below are the factors that contribute to the reduction ofroad capacity and level ofservice.
l. 2.
capacrty such as rain, fog, smog or wind.
Level
of,
Sen ice
The level of service is conrmonly accepted as measure of the restrictive effects of increased volume. Each segment of the roadway can be rated at an appropriate level from A to F inclusive to reflect its condition at given demand of service volume.
I-evel A B=
D: C
E =-
p=
Free
flow; speed control by driver's desire^ Stable Flow; erating speeds beginning to be restricted: little or no restrictions on maneuver abiliry from other vehicles. Stsble Flow; speeds and maneuverability more closely restricted.
Approaches unstableflow:tolerable speeds can be maintained but temporary restrictions to flow cause substantial drop in speed. Littie freedom to rn:ureuver comfbrt and convenience flow. Volume near capacity. speeds in neighborhood of 45 km./hr. Flow stable: stoppage of momentary duration. Abihty to maneuver is limited. Forced Flow: low operating speeds, voiume below canacitv.
392
Have 3.60 meters lane and 1.80 meters wide shoulder. Road with flat grades. Sight disturbance unrestricted No trucks or buses plying the route..
3. 4.
Narrorv lanes and shoulders, and restriction on
edge
clearance.
Sharp horizontal curves create dynamic forces to which drivers react. Short vertical curve over crests or obstructions to vision on the inside of horizontal curves causes vehicles to slow down. Commercial vehicles like truck requires more highway space per vehicle than the enger cars.
Effects of grade on uphill road, makes desirable vehicle spacing for higher road capacity. T\e 3o/o to 7Yo road upgrades does not affect enger c:trs unlike cargo trucks that are markedly affected by steeper grade.
Weaving Section Weaving section is defined as the crossing of two or more traffic streams traveling in the same general directions along a significant path of highway with the aid of traffic signal. The Traffic Circle Rotary or British "Roundabout" is considered series of weaving sections placed end to end. Likewise, a partial and full cloverleaf interchanges are example of weaving section. Vehicle entenng the freeway must wsave witl those leaving the freeway.
establishing level of service for.design purposes, each highway agency establishes its orm guidelines composed of two elements:
In
39:l
Elements of Roads and Highways
Traffic Engineering
l. The traffic volume served. 2. To proportion the basic freeway, weaving
sections, r:rmps and rarnp junctions to accommodate this flor,v at the designated level ofservice usrng appropriate data
il
TABLE 10-12 ENGERCAR EQUryALENT OFTRUCKS ON FREEWAY UPGRADES Four Lanes
Six or More Lanes
Grade o/o
2
2
2
t0
20
2
2
a -t
a
2
4
J
7
4
4
4
4
7
i
J
9
9
8
8
5
5
t4
IA
4 6
9
6
6
l3 l0
6
28
l8
!8
20
17
TABLE 10-13 LIMITING VOLUMES IN ENCL,R CARS PER HOT:R r.OR FREEWAYS AND ON AND OFF RAMPS FOR VARIOT,]S LE\'EI-S OF SERVICE AND PHF OF
T.OO
Freeway Volume in One
of Direction* Servicc Four lanc Levcl
A B c D E
Checkpoint Volumes Eight
lane Mergctr
Wcave
l)ivergesrtr
1600
3280
7fi
800
2500
5400
1200
3400
6800
15m
300 1650
Voluntet | * 1 500 700
1
1
300 550
3850
7700
1800
1900
1
(capacity) 4000
8000
2000
2000
2000
F"
Highly variable
Sourcc: TRB Circular 2 l2
t For 70 mph frccway dcsipln s1rccd tt Lane I volumc plus rarnp volunrc lirr onc lsnc ()rl rsnlps rtt 2 volume imnrcdiately upstrcarn ol'oll'rrrnp tt'r Lanc Wcave volumcs bclu'ccu ()rr rstlry. otl'rsrnp psir pcr 500 tl. of length 3c)4
l actors that Affect the Capacity and Level of Servicc
l. The Physical and operating width approaches. 2. The Physical and operating parking conditions. 3. Physical and operattng one way versus two way strocts 4 Environmental conditions - load factor 5. Environmental conditions - peak hour (r.
1 tt
Traffrc characteristics - turning movements Traffic characteristics - trucks and through buscs Traffic characteristics - local transit buscs
1-1 Brief History
of Roads
l-2 Early Laws that Regulates Roadway l-3 Highways in the Philippines 14 Planning Difficulties l-5 Highway Programming l-6 The Planner l-7 Community Involvement l-8 Highway Eeonorny l-9 Computation and Survey 1-10 Remote Sensing 1-l I Photogrammetic Mapping 1-12 Orthophotographs l-13 Colored Photographs 1-14 Locatron ofthe Proposed Highway l-15 Location of Bridges l-16 Highway Plans and Specifications
I 2 3
4 6 8
9 9
ll l3 t3 l5 15
16
2-2 Definition of 2-3 The Design Speed
24 Cross Section of Typical Highways 2-5
2-6
Road Shoulder Cross Slope Cut or Fill Slope
'T-he
2-7 2-8 Number of Lanes 2-9 Highway Median 2-10 The Grade Line 2-l I Vertical Curve Over Crest 2-12 Right ofWay 2-13 Stopping Sight Distance 2-14 T1rre ing Siglrt Distance 2-15 Road Alignment 2-16 Circular Curves
63
65 65 68 72
76 78 78
CHAPTER- 3 SOIL
3-I
Soil and its
Origin
79
il
3-3 Characteristics of Soil 3-4 Classification for Soils 3-5 Composition of Soil 3-6 Soil Reaction to Density 3-7 In-Piace Density and Unit Weight 3-8 R.elative Density
84 89
107
I02 103
T7
t9
CNAPTER-2 DNG THE HICHWAY
2-l Consistency
2-17 Super Elevation-Runoff 2-18 Widening of Curves 2-19 Island 2-20 Types of lnterchange 2-21 Highway Intersection at Grade 2-22 Freeway Entrance and Exit 2-23 Railroad- Highway Separation 2-24 Bicycle l-ane
23 23 27
29 34 42 43
46 46 53 55
56 57 59 60
6l
CHAPTER- 4 SOIL TEST AND SURVEY
4-I Test for Farticle Size 4-Z Test to Evaluate the Effect of Moisture 4-3 Density Test of Soil 44 Laboratory Test for Soil Density 4-5 Field Density Test of Soil in Place 4-6 The Strength Test 4-7 Soil Survey
106
r07 110 111 113
ll4 t20
CHAPTER- 5 ROAD MATERIALS
5-1
Aggregates
5:2 Aggreg:ile for Bituminous Pavernent 5-3 Aggregate for Portland Cement Concrete
Pavement 5-4 Mineral Filler 5-5 Bituminous Material 5-6 Bituminous Binders 5-7
Problems Associated with Bituminous
123 128 129 132 133 135
Binders
139
5-8 5-9
Bituminous Pavement Asphalt Concrete Pavement 5-10 Bituminous Pavement Failure 5-l Macadam Asphalt Mat
I
139
t4l t4r
142
5-12 Surface Treatnent 143 5-13 Aggregate for Bituminous Concrete 148 5-14 DPWH Standard Specifications on Prime Coat Tack Coat and Seal Coat t54 5-15 Geoplastic Fabrics t67
7-9 Construction of Fills and Embankment 0 Sub-Grade Preparation
7-l
7-l
I
8-l 8-Z 8-4 8-5
6-l
Drainage
t69 t7a
6-2 Hydrology
64
Drainingthe Highway
6-5 Manhole, lnlets and Catch Basin 6-6 Channel 6-7 Culvert 6-8 Design of Underdrain 6-9 Debris Control 6-10 The Legal Aspect of Drainage 6-11 Roadway Design and Construotion for 6-12 6-13 6-14 6-15
Unusual Soil Conditions Stabilizing the Unsupporred Slope Improving the Stability of Slope Retaining Wall
Highway Bridges
172
t75 t77 t79 190
r92 193
193
r97 201
204
2t5
CHAPTER- 7 CONSTRUCTING THE ROADBf,I)
7-I 7-Z 7-3 7-4 7-5
Soil as Sfucture Types of Base Course Treated Base Course Grading and Maintenance of Untreated Surface PWH Standard Specifications on Aggregate Sub-Base Course Clearing and Grubbing
7-6 7-7 Excavation 7-8 Free Haul -
227
23s 237
Overhaul (Item 107)
8-6 8-7 8-8
Portland Cement Concrete Pavement Characteristics and Behavior Control of Cracks Transverse Expansion ts Longitudinal ts Construction t Reinforcement of ts The Sub-Grade and Sub-Base for Concrete
244
253
254 257 257 259
260 261
Pavement 262 Proportions 263 Mixture 265 8-l I Polymer Concrete 267 8-12 Curing of Concrste Pavement 267 8-13 DPWH Specifications on Concrete Pavement 268 8-14 Equipment 274 8-15 Preparation of Grade 276 8-9
Concrete 8-10 Concrete
8-16 Flandling Measuring and Batching of Materials 8-17 Placing or Depositing of Concrete 8-18 Finat Consolidation and Finishing 8-19 Curing 8-20 Removal of Forms 8-21 Concreting bythe Slip Form Method 8-22 Tolerance and Pavement Thickness
2t9 22A 222 225
248 248
CHAPTER- 8 CONCRETE PAVEMENT
8-3
CHAPTER{ DRAINAGE AND SLOPE PROTECTION
Compaction and Stabilization
241
CHAPTER_
278 280
285 291 293 293
296
9 ROAD MAINTENANCE
maintenance management Rehabilitation Evaluation and maintenance of concrete
9-l
Highway
299
9-Z 9-3 9-4
Maintenance
303 307 313
pavement
9-5
Highway and its environment
315
9-6 Highwaybeautification 9-7 Environmental laws
9-8 Environmental elfects of highu'ays 9-9 Construction and relation to roadside
3t7 318 319
CHAPTER
321
development
9-10 Vegetation and the highways 9-11 Parking and rest areas
321 323
THE HIGHWAY AND ITS DEVELOPMENT
CHAPTER-I0 TRAFX'IC ENGINEERING
l0-l
Road
traffic signs
I0-2 Basic principle of road signs l0-3 Warning (Danger) signs l0-4 lntersection signs l0-5 Prescription sign l0-6 Obligation signs l0-7 End of prescription signs 10-8 Direction
signs
l0-9
Informatrve sign
10-10 10-l I 10-12 10-13 10-14 10-15 10-16 10-17 10-18 10-19 10-20
Traffic signals PavEment markings Guidepost and markings Guardrail Concrete barrier Highway and urban street operations Traffic control Freeway and expressway operation
Sreet lighting Streetparking Highway capacity and level of service
325
328 329
334 339 343 345
346 349 352 360 372 377 379
382 385 386 388
390 391
1-1 Brief
llistory of Roads
Early roads with hard surfaces were found in the land of Mesopotamia. These roads were constructed as early as 3,500 B"C. Another stone surface roads were also found in the Mediterranean island of Crete, similarly constructed as those in the Western Hemisphere by thc Mayans, Aztecs and the Incas of Central South America.
The early road systems were constructed primarily for the following purposes:
l.
For the movement of armies in their conquest and for defense against invasion.
7. For transport of
food and trade
of
goods between
neighboring tovms and cities.
The Romans, who discovered cement, expanded their vast empire through extensive road networks radiating in many ditrciions from the capital city of Rome. Many of the roads built by the Romans still exist even after 2,000 years. Characteri.stically, Roman Roads were laid on three courses
L 2. 3.
A layer of small broken stones. Followed by layer of small stones mixed with mortar and then compacted firmly. Wearing course of massive stone blocks properly set and bedded with cement lnortar.
Elements of Roads and Highways
During the l7s century, under the rergn of Napoleon the Great, made a great stride on road buildings. Jerome Tresaguet (1716-1796) the famous French Engineer introduced new methods of construction and maintenance of stone roads. He improved the crown" the drainage, and the grade of the road, including the stone foundation by reducing the depth of broken stones to 25 centimeters. Tresaguet made it possible fbr Napoleon to build the massive highways of , He was accredited the title "Father of modern road building. Thirty years later, a Scottish Engineer born in Westminster Abbey, Thomas Telford (1757-1834), president and founder of the lnstitute of Civil Engineer, introduced.some improvements in the construction methods of Jerome Tresaguet. The road foundation course of Telford was made of stones having 3 inches minimum thickness. 5 inches breadth and 7 inches height. Smaller stones were driven by mauls on top voids and trued the surfaces by breaking the projecting points. Telfbrd employed a flat sub-grade, providing slight crown using stones of varying sizes. England followed the ongoing highway development started
by . The
Macadam road concept named after John (1755-1836). another famous Scottish EnMac Adam Louden gineer road builder and contemporary of Telford, was developed and widely accepted. The invention of road building equipment enhances the development of roads in Europe. In 1858, Eli Blake invented the first stone crusher and at the same period, a steam road roller weighing 30 tons was inlroduced in by its inventor, Aveling and Porter.
l-2
Early Laws that Regulates Roadway
The early Saxon Laws imposes three mandatory duties for the people to perform, namely: To repair the roads and bridges. To repair the castles and the garrisons To aid repel invasions.
l. 2. 3.
_l
The Highway and its Development After the Norman Conquest of England, it was decreed that:
1.
2.
The king's Highway is sacred. Anybody who occupies any portion thereof, by exceeding the boundaries of his land, is considered to have encroached on the king himself. Roads are for public use. All persons who want to use them may do so.
Properf owners ading the roads were required to drain the road, clip any bordering hedges, and refrain from plowing and planting trees, shrubs, or bushes closer than the specified distange from the csnter of the road.
It
was made clear that the govenment concept towards the: use of roads inciudes upholding the right of the public to use them without interference. Since the road is intended for the benefit of the people, fur return, it becomes their duty to protect and maintain the roadway.
1-3 Highways in the Philippines In the early part of 1900, transportations in this country depended largely on trails, waterways, railroad, earth roads and partially graveled roads. Highway in the Philippines at that time is nottring more than a dream to most Filipinos. The American government initiated the development of roadways in the Philippines, connecting towns, cities and provinces. The popular Macadam road type was introduced. It gained wide acceptance because ofthe abundant supply ofstones and gravel.
After the Second World War, the new independent Philippine govemmen! continued the rehabilitation and construction of roads and bridges, through the reparations and war damages paid by the Japanese government. Otler financial grants and aids received from the U.S. government were used in the construction and rehabilitation of roads and bridges.
Fifty years later, major highways and expressways were constructed through the financial assistance and loans from
Elenrents of Roads and Highways
foreign banks. Alongside with the industrialization program of the governrnent, vehicles of various types and sizes started
flooding tle roadways. Recent Land rranspor[ation records revealed that, more than 80,000 brand new -,rehicles were added to their lists everv year. At an average of 5.00 meters road occupancy by these vehicles, the DPWH must open 400 kilometers new roads every year. This data did nr:t include ),et the roaclway for second hand or surplus assembled cars. with this statistical
report, solution to traffic problems is nowhere insight. Traffic problems are expected to worsen year after year.
The 1.ear 1960 to early part of 1980 rvas consitlered an autornobile age. Cars were no longer regarded as luxury item but a necessity in transporting people and;oods, a necessity for survival, Government new concept of development is to get the farmers of the mud. It was during this clecade that road construction'ut becornes a matter of priorit-v of the governrnent under the slogan: " This nation is on Wheels,,.
1-4 Planning Dif{iculties Devefoprn*nt and maintenance of'roads ancl highways is a contmurng process alongside wrth the technological advance_ ntent. New equipment and management techniques revolution_ ized, the construction and maintenance mcthods. Advance knowledge in the field of soils, highway materials, and designs were adopted for reliability and economic considerations. Engineers are conscious
ofthe need for roadways to be safe, useful, and attractive. This needs include improvement of the roadside, erosion control, and noise abatement. They are aware
of the fact that highways are vital to the country's development. Unfortunately, highway planners are confronted with problems categorized as follows:
l. 2. ,j.
Financial
Political and 'fechnical
The Highway and its Development
The present economic condition is related to the government budgetary expenditures fbr payment of foreign clebt arnortization amounting to billions of pesos a month. Appropriations of funds for road cnnstructions and maintenance, meet severe
difliculties that sornetimes, highway development plans
are
shelves temporarily for lack of funds.
Comprehensive road development plans that are carefully studied by technical experts are twisted, or flexed down by political muscles, to suit political interests" Roads and highways plan were either; deferred- arnended or realigned for political reasons. As a consequence, different laws with conflicting purposes and procedures impede or obstruct implementations causing delay or no action at all"
Politicians now control DPVIH projects as their source of,
political funds. Highway district engineer's qualification is simply subservience to the politician. "Do wlrat I say or get out of my district". Listing of projects given to the district engineer has the corresponding name of favored contractors- the willing victims giving SOP in cash adrances.
Rational Planning is no longer the objective process, based on training, and expertise conceming the actual needs of the: people, but is rather, a political decision. Not even the Secretarl' of Public Works and Highways could say no because politics is the power that controls appropriations, budget and appointments of the president's cabinet .
As a consequence, public confidence tremendously eroded. not only in the government's ability to abate these problems, but also in the proficiency of the technical men to offer solutions. Planners are now operating in a world of rapid change. and uncertainty, in the political atmosphere where decisions by magic, or oracles, carry more weight than those based on professional training, expertise and experiences. Indeed, our professionals more particularly the technical men, seems tc have lost confidence in thyself, or eventhe solutions that they oftbr.
Blements of Roads and Highways
The Highway and its Development
1-5 Highway Programming
Direct Effects of Highway Construction and its Use
There are three inseparable sets of irrputs involved in highway progr:unming, they are:
A" Quantifiable market value l. Cost of highways as to:
l. 2.
Ecnnomic - Deals with the questions of resources. f inancial - The question of'who pays and who spends,
3.
horl much, and where? Political and istration - This invoires decision
a. b. c. d. e.
making.
trn highway programming, projects are prioritized. Those that are most economically viable were selected, if they fit into the financial capability and of course political criteria. Projects that failed on either financial or political criteria are abandoned, modified for substitute, or an alternative but shall ed rigor-
2.
b.
Highway Prograrnming Approaches
l. 2. 3. 4. 5"
c.
Financial resources are either short or long ranged implementation by the agencies functions like construction, operations, and maintenance.
Recognition
of the legislative and
istrative desire
and constraint.
Tentative priorities based on economic analysis, critical situations, present and future expected level of traffic, and
l.
7.
operation per year
Travel savings time (commercial). Net increase or decrease in travel time multiplied by the peso value of commercial time.
Motorist's safety (economic cost accident) Net change in expected number of accidents times
Cost benefits to highway :
a. b. c.
materials, including climatic conditions.
final plan and specifications. Budgetary reserve to cover emergencies like floods and other natural disasters.
Vehicles operating costs (including congestion cost) net income or decrease in costs of vehicle
B. Non-Qu antifi able Non-Market Valu e
Providing continuity of route system and coordination with other transportation mode. Selection of projects based on availability of labor and
the project implementation in coordination other agencies, acquiring right of way and making
Maintenance costs. Operating costs.
the average cost per accident per year.
claims based on political subdivisions.
6. 'wrth Scheduling
Constnrction costs.
Cost benefits to highway s
a.
ous tests.
Planning cost. Rrght of way appropriations.
Motorists safety - Accident cost of pain suffering and deprivation.
Comfort and conversion - Discomfort, inconvenience and strain of driving.
Aesthetic fiom driving viewpoint
-
Benefit of
pleasing views and scenery from road.
C. Quantifinble Non-Market Value
l.
Cost benefits to highway s - Traveling savings time. (non-commercial) Minutes save per vehicle trip.
Highways and its Development
Elements of Roads and Highways
4.
1-6 The Planner
Secure formal ratification
fiom the local officials
have the results documented
Before any project comes to reality, it has to undergo rigorous and careful studies with participation of several line agencies involved. Where proposals may be opposed or questioned by other agencies, or in the political mill, the planner appoints coordinators or catalysts, to work out in exchanging information as to the needs, goals, and altemative solutions of those who are affected, and to incorporate them into the planning and decision
lf
and
nothing goes wrong, this
step is considered final.
Good ethics demand that planners should understand that their role is to provide.knowledge and unbiased information. To be partisan and emotionally involved, will only jeopardize their credibility. 'Ihis might give them the feeling of personal defeat and disillusionment with their profession, if the solutions that they offered are only throqm into the trash can"
making
Where planners act as coordjnators, catalysts or to work as community advocates, should not be either partisan or advocate to a particular soiution. Their role is:
L 2.
To provide technical and organizational . To receive mput or information on the needs and goals
3.
affected persons group or agencies. Incorporate the above for planning and making decision.
The Functions of the Planners are:
2.
To prepare preliminary design, scoop of study and the initial work program. Know the basic needs, plan and objectives ofafilected persons. Exploration of alternatives. Data gathering by ing the representatives of other agencies involved.
Detailed analysis. Prepare detailed plan community interaction.
for
Community Involvement
In a democratic government, the public has the right to hear and be heard. Much more to participate in public hearirry where planning and decision making
of
The planner's role must be of a clarifier, expediters, conciliators and impartial negotiators. The myth of rationality must be avoided because they might believe that as professionals, they are uniquely super qualified to judge what is best for the society in their field of expertise and competence. They must accept that their personal values and goals are different from other participants.
l.
l-7
appropriate
will be conducted before
maior
decisions are made.
It is a corrunon practice to call public hearing after all major decisions were rnade and approved. Indeed, public hearing is no more than information forum for the public to know what the
istration wants for them, rather than, what the people wants from them. Public hearing should involved the public from the start of planning to give them a chance to participate in the discussions and involved thern in:
l. 2. 3. 4.
Solicit the cooperation and of public ollicials, non-goverrrment organizations, influential persons and conservative group of the community. Create special staffto carry out this function Comrnunity leadership opportunity to participate continuously rn the planning stage. Organize and develop skilled persons to conduct group meeting, workshops, hearing and other related activities.
1-8 Highway Bconomy A Country who will not avail of loans or grant from foreign
Elements of Roads and Highwnys
The Highways and its l)evelopment
financing institutions will not fbel the great impact of their infrastructure projects, if dornestic income through taxes alone will be depended on. Financing institution such as the World Bank insists that projects to which they make grants or loans be justified primarily on the economic basis. According to W. Gillespe, professor of Civil Engineering at the Union College:
Legally, the appropriation and expenditures of taxes being the people's contribution to the goverffnent must be prorated proportionally to the different provinces municipalities and cities in of infrastructure projects and not just be concentrated in specific place. Under that principle, progress of the country would be very slow considering the meager amount each province will get, and the infiastructure it will accomplish. l{ence, borrowing from foreign banks is the ultimate solutions of the government to deliver impact infrastructure projects to boost the economy and move quickly forward.
"A rninimum of expenses is of course, highly desirable; but the road which is truly the cheapest is not the one which has cost the least money, but the one which makes the mast profitable returns in proportion to the amount expended upon it. " There are many designs and istrative decjsions that does not involve public policy, but these should be made by selecting the alternative that is cheapest in the long run. Meanrng'. the result .from an econornic study tl.tat is reasonably interpreled musl prevuil.
The intent of expenditures for highways and public transportations are enumerated as follows:
]. To 2. 3. 4.
augment the country's level of economy. To provide easy access to working place. To facilitate public services; police, fire protection etc. To facilitate medical care, schooling and delivery of re-
5.
lated basic services. To give landowner benefits to transportation and increase
property assessment. Benefit to motor vehicle s through lower cost of operations and maintenance. 7.
Benefit in time saving.
8"
Less road accident.
9
To give maximum comfort and ease of travel.
Most of the country's expenditures for highways and public transport facilities are based on the principle of "Pay as you go,, Meaning, road appropriations and expenditures depend on tax collections. t(,
Arguments of those who Favors Borrowings are:
i. The need is immediate to have instant infrastructures. 2. No impact project will be seen because tJre "pay as you go" fund is scattered through out the entire road
3.
system
where the situation is most critical. Borrowings encourage investors because offast progrcss.
Counter Arguments of those Against Financing Infrastructures through Borrowing:
l. 3.
Borrowing may impair the credit rating of governrnent agencies obstructing other more important improvements. If future income is committed to pay past improvements, no more funds available to rnaintain the existing system. With much ;rmount available temptation is there to over
4.
build and recklessly spend extravagantly. Interest of the loan is a big waste of public funds.
2.
1-9 Computation and Survey Early engineering approach to highway and transportation problems were based on the results of their computations with the aid of slide rule and replaced by calculator machine. This method is time consuming and was totally discarded in the advent of computers and its appurtenances.
ll
Elements of Roads and Highways Today, most of the agencies have their oun da[a processing and reporting is done through cornputer networts. Engineering
approach
to highway
and transportation problems are done
through computer output from the simple to cr:mplex matters. Computers can do processing dota for many problems like:
l.
Projections and statistrcal studies of traffrc and transit engers.
2 3. 4. { 6. 7" 8.
9.
ror
if correctly programmed. On the other hand, too much reli-
ance on this machine might be a trap for the uninformed to assume that the program inputs are absolutely correct. Deeper analysis and professional attention to computer program is the key to accurate results that could be the basis for good deci-
1-10 Remote Sensing
Geometric. Bridges. Pavement design and maintenance. Pavement management. Scheduling for design and construction.
Computation of earthworks and other quantrties both for planning and payment of contractors.
with stereo plotter fbr map makrng
and location identification. The computer base
interactive screen, focused on
graphics could present problems into the technical matters and management decisions making lata. Various computer programs are abundantly available to solve the repetitive highway and transportation problems.
The computer graphics display a motorist view of the highway so that the engineer could make appropriate treatment of certain portion as transition from cut to fills, route, location, traffic, and transportation planning and accident analysis. The interactive graphics is used without computer, referred to as environmental simulation^ A remote controlled television camera es through small scales physical module of the area or route. The age is recorded in the tape and the playback will show impression similar to that of the walker on the road or the vehicle driver. t2
With the aid of sophisticated computers and its appurtenances, engineering practice today is not as difificult as the time of slide rule era. Computers are less prone to computational er-
sions.
Economic analysis. Financial programming.
Con"rputers are provided
The tlighways and its Development
Remote sensing is otherwise called Photogrammetry. It is the science and art of obtaining measurements by means of photography. Photogrammetry is based on aerial photographs for engineers working data on:
l. 2. 3. 4. 5. 6. 7. 8. 9.
Locations. Planning. Geometric design.
Right of way.
Traffic studies. Drainage.
Soil classifications and identifications.
Earthworkmeasurements Material location. 10. Pavement condition survev
1-11 Photogrammetric Mapping A vertical aerial photograph taken by a camera pointed almost straight downward is the most useful mapping for highway purposes. The area to be covered is photographed in parallel runs with the individual pictures lapped in the direction of the flight (end lap) and between successive runs (side lap). For stereoscopic uses, the following must be considered:
I
End lap must be greater than one half the picture width
l3
The Highways and its Development
Elements of Roads and I{ighways
2. 3.
specified not less than 55Yo nor more than 65%o in order that the center ofone picture is included in both adjacent photograph. Side lap should average at25o/o with less than 15. More than 3 5 o/o i s unacceptable. For making map purposes, the variable includes the focal length of the aerial camera, the desired combination of
map scale and contour interval, and the ratio of map scale to photograph scale.
Instruments used in converting data from aerial photo-
graphs into maps are:
]. The Kelsh and Balplex 2.
stereoscopic plotters
The wild autograph
'lhe Kern PG2
4.
The Zeiss Stereoplanigraph
Features that cannot be identified on the photographs are located by grounci measurements foy important poinfs to be included on the ground surveys are marked for easy identification on the photograph. Accuracy ofthe ground control triangulation network is when scaled with the aerial photographs. The third order triangulation is acceptable in rural areas, and the
for urban locations wherein the
maximum errors in distance are I to 5000 and 1 to 10,000 respectively. An accurate angular triangulation measurement is easily obtained by the use of Modern Theodolites. The distance measurement is carried out by an electronic distant measuring device (EDM) that employ infra red light beams, microwave or laser light. I
I
Profiles Cross sections
Cut and fill earthwork quantities The motorist view of the road
With photographs and computer record data, a separate map could be plotted easily like:
l The highways 2. The drainage 3. Housing 4. Land use and zoning 5. Property assessment The ground field survey is done only as supplemental in
J-
second order triangulation
1. 2. 3. 4.
The Photogrammetric technique coupled with digitizer, produces digital terrain models. The horizontal and vertical positions ofthe ground surface, and other photographic features are directly transferred from the matched aerial photograph to a computer data bank. The information is recalled and the computer is programmed to develop showing the following:
completing the details of those that could not be produced in the photographs.
1-12 Orthophotographs Orthophotographs is an aerial photograph corrected for scale and trlt. When the center portiol are skillfully matched and copied, they appear to be a single photograph that shows far more detail than maps. The uncorrected or partially corrected photographs are combined to form a mosaic, considered better for engineering accuracy and right ofway purposes.
1-13 Colored Photographs Aerial colored photograph presents a more detailed and precise information on traffii and parking studies. It gives clear information of the geological conditions, land use, source of materials, surfaces and sub-surface drainage. An oblique photograph is used for special studies particularly, where the ground condition is almost flat or where cliffs are so steep that a black and white photograph could not give sufficient details.
I
14
l5
I'he Ilighways and its Development
Eleltrents of ldoads and Highways
l.
l-14 Location of the Proposed Highway Early roads started from trails. Movements of people and the use of motor vehicles prompted road agencies to improve road alignment minimizing sharp curves. Road width was standardized and grades were flattened. New highway locations are trlended witJl curvature grades and other roadway elements to offer; comfortable easy driving, free flowing traffic arteries, comply with the rules on safety standards.
To improve the highways, there should be tentative plan as to the control, and minimum design speed, roadway cross sec-
2. 3. 4. 5. Stage
1.
tions, and maxlmum slope with the following considerations:
l. 2. 3. 4.
Rpliable cost cstimate. Character and hourly distribution of traffic. Economic and community benefit facLor. Availability of funds.
2.
2. 3. 4.
Reconnaissance survey of the entire area between the terminal points. Reconnaissance survey of all feasible routes. Preliminary survey of the best route. and the structure for construction.
Activities
l. 2. 3.
I
Reconnaissqnce survey of the entire area
Stereoscopic examination of small scaled aerial photographs of the area supplemented by available maps. Determination control of photography and land use.
L.ocation
of feasible routes based on photographs
maps.
Under stage
l6
II
Reconnaissance survey offeasible route:
Survey af the hest rou(e.
Preparation of large scale t,:pographic maps ustng the route photograph and Photogrammetric methods or preparation of, large scale topographic maps b-v'' ground survey guided by best route location made on photr:graphs in the second stage. Design of the preliminary location
IV Locafion 'Swn,ey
Staking of the right of way and the highway and structures for construction"
1-15 Location of Bridges
Location survey, staking of the right of way, the highway
Under stage
III Preliminary
Stage -
Locstion surveys in the rural ureas are divided into 4 stages.
l.
Stcreoscopic examination of largo-scale aerial photographs ofeach route. Detennination of the detarled control of pirotography and land use. Preparation of route maps by Photogrammetric methods. Location and comparison of feasible routes on photographs and maps" Selection ofthe best routc"
arrd
Highways and Bridges have but one purpose - To convey traffic. The location and position of a bridge is subordinate to the general alignrnent and grade. But sometimes, fuvorable alignment has to be sacrificed, only to provide a right angle crossing to small creek. Lately however, the general policy for minor roads is to determine the proper highway location, then provide the structures. A skewed bridge is comparatively more expensive than the right angle bridge. The horizontal and vertical curvature shape of large bridge presents serious design and construction problem, but the finished product may result to a better roadwav. Foundation design of piers and abutments has large effect on costs, but cost is not alw'ays the determining factor in design.
The Highways and its Development
The Highways and its DeveloPment
The cost of a bridge and its full approach cornbined before the crossing site should be determined. Bridge survey report should be accompanied with accurate data on the waterway and the historical behavior of the water. The bridge survey data shall include the foundation conditions, stream characteristics, and the adjacent structure on the stream more particularly, waterway opening.
tleir
When the location of the bndge is approximately deter-
1-16 I{ighway Plans and Specifications Plans and specifications are set of documents of instructions and conditions under which highways and bridges are built. The plan contains engineering drawings of the prolect, whereas, the specifications is a written instructions and conditions considered as integral part ofthe contract between the contractor eutd highway agency classified as legal documents.
mined, the following requirements must be considered:
1. 2. 3 4. 5. 6.
A complete data report and special survey of dre site. Prepare sketches and full scale map and profiles. The survey report must contain accurate data of the waterway for all behavior of water. There must be a complete report on the foundation condition and the stream characteristics. A complete data of the adjacent structures particularly the waterway opening.
If possible,
skewed bridge should be avoided.
The complete detailed scheme for the road which are incorporated in the geometric designS are:
1.
2. 3" 4. 5. 6. 7.
Traffic Drainage
Erosion control Roadside development
Structure Soils Pavement
Presentation of a Road Plan
l.
Source: HigthwcY Engineeing bv Calesbv ond Hicks
The upper sheet is allocated for the plan, top view showing the horizontal alignmenl, right of way takings, drain age arrangement and other features. 2. The lower half is allotted to the profile where the original elevation of the ground surface is plotted. The roadway centerline and the vertical alignment or grade line for the road is indicated. 3. The vertical scale of the profile is usually exaggeratedly enlarged from five to ten times for precise detatl. The profile and other details of the drainage, channels or connecting roads including ramps are also presented. 5. The estimated earthwork quantities for every 50 meters
station or other intervals are indicated along the bottom of each sheet along with the estimated overhead. This FIGURE 1-1 TYPICAL EXAMPLE OF SMALL BRIDGE LOCATION PROBLEM
l6
will
serve the engineer and the contractor.
l9
I lr*.
Elements of Roatls and I'iip,,ilwavs
liighwars rln{l its ilevelopment
'tr'he rolr.lwav riross sections for every situation in the rvhole pro";cr:t stretch is indicated on another sheet of the plan.
Another shcet
cf
drayiings showing
all
structures and
roattrway appurtfin;rnces ls included.
The standard sizc of
ther
drawins sheet is 55 cm x 90 cm.
Ilartial list of suhicets c.overed by the standard drawing:
1. Fipe culr,,*rts. 7. tloncr*tc box cLriverts. 3. Guard r;ril au<J pil.riipet, 4. Curbs. 5. Cutlcrs. tr Curh:lnrc'turcs '1 5 rdq:ri;rl[,s 8" Drainag* intct anil outlet structures of numerous types. 9. Manholcs" .
{ () =
o
.
3!;i .i;
J
lril
3
f
'n; l k: r:a
r{
&.
+{-
i*
v
t
ut
z
Io a
l:
F
qt
ll.
tt
o
z
.;
5
d!i
;
A. oJ UJ
t f,
o l!
10. Rip-rap and other devices used for bank protection. I l. Fences and right of way. 12. Other survey rnarkers.
The Specifications Specifications writing is generally different and a delicate rvork requiring lcnowledge of the law of contracts as well as highway practices and experiences. Specifications that are carelessly written and loosely worded may result in the use of substandard materials and poor workmanship. Mostly, it involves extra cost to the owner or the contractor and sometimes landed in court litigations. On the other hand, specifications that are too restrictive are very costly.
d a
o
Flighway Specifications is Divided into Two:
l.
2A
Stondard Specifications applies to project implemented by istration which treat the subject that repeatedly clccurs in the agency work. 7_i
Elements of Roads and Highways
2.
Special Provisions covers peculiar item of the project in question that include additional modification to standard specifications. This includes copies of all documents required in securing cornpetitive bids and contracts. Specifications are also subdivided into two: a.) The general clause that deals with the bidding procedures and award execution and control of work and other legal matters. b.) Specifuing detail regarding the materials, manner of work execution and how pay quantities are to be measured.
CHAPTER
DEG THE
HIGHWAY 2-l
Consistency
Consistency is the most important single rule
in highway
design. That is, by making every element of the roadway conforms to the expectation of every driver.
Drivers expect the highway agency to provide them with:
l.
Clear information and guidance tlrough a variety of road
2.
Avoiding abrupt changes in the traffic as well as the road
slgns. standards.
If these guides and directions could be planned properly to convey one single message at a time, and if these directions will be followed smoothly and easily without undue haste, or changes in speed, lhen, the roadway facilities are considered satisfactory. Experienced highway Engineers recommended that highway signs and directions should be integrated as early as the preliminary layout studies.
2-2 Definition of AASTHO is the American Association of State Highway ln 1914, the American Association of State Highway Officials (ASSHO) was established as an association of State Territorial and District of Coi.rmbia Highand Transportation Officials.
way Department, and the Federal Highway istration. The L3
Deg the Highway
Elements of Roads and Flighways name was expanded
in
1973, when the Departrnent of Transpor-
tation was integrated into the association renaming AASHO to AASFilO, giving the officials of these agcncy the power to govern its operation. Engineering activities, were implemented by the standing committees with the task of preparing specifications manual and standards, representing the current trighway
Control of Access is a conditron where the rights of owners or occupants of ading land or other persons access to light, air or view in cormestion with a highway is fully or partially controlled by public authority.
engineering practice.
Full Control of Access - The authority to control access is exercised to give preference to through traffic by providing access connections to seiected public roads only. Crossing at
AASIIIO
grade or direct private driveway connections is not permitted.
l. 2. 3. +.
publications includes:
Transportation Materials Specifications and Tests. Specifications for highway bridges Geometric deign standards. Numerous policy statements and guides.
Partial Control of Access - The authority to control access is exercised to give preference to through traffic. Although in addition to access connestions with selected public roads, there may be some crossings at grade and some private driveway connections allowed.
AASHTO publications are authoritative" References are made in these books and periodic manuals. 'lhe association also publishes the AASHTO quafterly reports on current Highway and Transportations sublect including trends in forecast and legislation.
Roads and Highways is defined as strips of land that have been cleared and further improved for tle movement of people and goods.
Road. R.oad has somewhat broader application in usage while generally used to describe a public thoroughfare. It can
Through Street or Through Highway - Every Highway or portion thereof on which vehicular traffic is given preferential right of way, and at the entrance to which vehicular traffic from intersecting highways is required by law to yreld right of way to vehicles on such through highway in obedience to either stop sign or yield signs erected thereon.
Parlanay is an arterial highway for non-conrmercial traffic, with full or partial control of access usually located within a park or ribbon park-like development.
also refer to railways.
Highway" The term was first used in England to describe a public road built by digging ditches on both sides and heaping up the earth in the middle creating a way higher than the adjacent land. Highway now connotes, a higher state of development than road. but the words are almost interchangeable.
Expressway is a divided arterial highway for through traffic full or partial control or access and generally provided with grade separation at major intersections. wrth
Freeway is au expressway with/r Il control
oJ"
access"
Arterial Street is an arterial route that carries traffic to the nearest access point or through traffic. It often serves as the most advantageous routes for relatively long distance travel.
Most arterial streets are existing highways of considerable length along which cross traffic is regulated by signals or stop signs. In addition, arterials provide access to adjacent property but often with restrictions on entry and exit points. Arterial street is considered as a "make do" substitute for controlled access facilities when traffic volume exceeds about 20,000 vehicles per day.
I
t
Deg the HighwaY
Elements of Roads and Highways Basic Considerations in Planning Arterial Roadways
l. 2. 3. 4. 5. 6. 7. 8.
ernment.
Accident experienced. Width should not be less than 15 meters. Must carry at least one lane oftraffic in each direction. Should be at least one kilomster in length. Should skirt neighborhood areas rather than penetrate
a given period of time usually expressed as vehicles per hour.
9.
On gnd desrgn system streets, arterials are spaced at about 600 to 900 meters apart. 10. Where accident hazard is not a factor, the minimum volume to justifu arterial road is 300 vehicles per average hour during the day, and 450 vehicles hourly during peak periods.
Sometimes, peak hour traffic volume on designated arterial road exceeds the capacrty of two-way streets, and to increase the arterial capaclty, the following solutions are enforced:
2. 3. 4. 5.
defined as a road constructed and maintained by the local gov-
Selection of the routes. Studies of the traffic volume. Origin and destination.
thern.
l.
to residence, business, or other ading properties. It is also
During peak hours, parking is prohibited on one or both sides ofthe street. Parking is prohibited several meters away from each side ofthe road intersections or corners. fughtturn is allowed on red signals anytime with care. Left turns are eliminated on congested intersections. The direction of traffic is reversed in the center lane to provide more lanes in the direction of heavier traffic flow
Collector Street form smaller mesh grid pattem where engers are pick up from service streets and carried to the arte-
rials. Large commercial enterprises or amusement facilities like drive in theaters are mostly fronting arterial roads. Local Road is defined as street or road primarily for access
Highway Capacity is defined as the manimum number of vehicles that are reasonably erpected to a given point over
l.
Under ideal conditions, one freeway lane can accommodate about 2,000 enger cars per hour.
2.
Two-lane road can carry up hour in each direction.
to 1,000
enger cars per
There is an obvious relationship betwe€n vehicle speed and highway capacity. As the volume of traffrc approaches capacity, the average speed is markedly reduced.
AADT or ADT refers to traffic volume or flow on a highway as measured by the number of vehicles lng a partial station during a given interval of time. It is called 'Average Annual Daily Traffic" if the period is less t}an one year. Volume may be stated on houdy "Observed Traffic Volume" or estimated 30e hour volume commonly used for desrgn purposes. Some highway agencies use traffic volume for 5 minutes interval to distinguish short peak movements of vehicles.
2-3 The Design Speed There is no single sst of Geometric Standards that will apply to all highways. For every highway segment, decisions reg-di"g appropriate control for each of the many details or requirements must be addressed individually or separately.
AASI{TO defined Design SPeed
as:
"The speed determined for design and correlation of the physicat feature of a highway that influence vehicles operation' 27
26
Elernents of Roads and Highwnys
Deg the Highway
It is the marimum'speed that can be maintamed over a specified section of the highway when weather and traffc conditi.ons are so
favorable that the designfeatures af the highway govern.
Basic Design Features refers to the tightness and super elevation ofcurves, the sight distance, and grade. The design speed
is
basically higher than AASI{TO recommend that:
the
anticipated average
speed.
"The design speed be set to the greatest degree possible, to satisfy the needs of nearly all drivers bath today and throughout the road anticipated life."
obsolescence as well as the increased margin of operating safety. The high speed road design must anticipate future generation high speed vehicles and advanced transportation systems that may operate on many of these road alignments. Although the design speed of most highways is govemed by construction costs, the concept of the relatively high speed design for freeways is Regardless of Cost. They are planned for a nationwide high volume traffic and high speed network.
TABLE2.l MINIMU
For economic reasons, the Geometric Features of certain road sections are designed for speed from 30 to 50 kilometers per hour. And yet, some motorists drive faster on straight road alignment or less sharply curved sections. Under this situations, highway des4n adopted control by reducing the super elevation combined with easement curves, delineators, stripprng signs and rumble strips, to alert motorists and inform them tha! they are approaching sharp curves or blind curves. Selection of the proper road design speed is one of tlre most important decisions to make, because it sets the limit to curvature, sight distance, and other geometric figures. But because of limited funds, there is a strong ternptation to reduce the design speed. Such kind of decision is unwise, because the alignment grade and siglrt distance after the roadway has been construct€d and paved along the landscape and rights of way, become more difficult and expensive to adjust or to correct.
The AASHTO practice is to classify first the highway as Rural or Urban, then as Freeways, Arterials, Coliectors and Local. Rural collectors and local facilities are classified as flat, rolling, or mountainous. Although the design speed presently used is 80 lan. per hour, highway designers projected design speed up ta 120 kilometers per hour to guarantee against future
28
ECOMMENDEI' DESIGN SPEED
FACILITY
RURAL Km/hr 8G95 preferred 6495 but 48 in built
Freeway
Arterial Collectors Local
110-95 mountainous 80- I
l0
up areas 48 km./hr.
See Table 2-2
32-48km./hr.
See Table 2-2
TABLE 2.2 AASHTO MINIMUM DESIGN SPEEI) KM./HR FOR RURAL COLLECTORS AND LOCAL ROADS BASED ON CURRENT ADT Class
Collector
0-400 Level
4W-750
750-2000
Tra 2000-4000 Over 4000 75 90
60 45
75
I>
Rolling
60
60
IJ
75
Mountainous
30
45 50-250 45
45
60
60
250-400
Over 400
Local
0-50
Levcl Rolling
45 30
Mountainous
30
45
60 45
30
30
75 60 45
2-4 Cross Section of Typical Highway The cross section of a typical highway has latitude of variables to consider such as:
Deg the Highway
Elements of Roads and l{ighways The volume of traffic. Character of the traffic. Speed of the
traffic.
Characteristics of motor vehicles and of the driver
Highway design usually adopted cross section that is uniform in thickness from end to end of the improvement. This is acceptable on high volume traffic road facilities. For a low volume traffic facilities, modrfication of the features like the shouldcrs width in rough areas are usually employed to reduce costs. A cross section design generally offers the expected level of service for safety and a recent study showed that: t.
A
7.20 meters wide pavement has l8% less accidenl compared wrth pavement narrower than 5.50 m. wide.
A 3.
4.
7,2A meters wide pavement ha 4%o fetver accidents
than the 6.00 meters wide roadway. Accident records showed no difference between the 6.60 meters and the 7.20 meters wide pave.ment. For the 6.00 m., 6.60 m. and,7.20 meters wide pavement with 2.70 to 3.00 m. wide shoulder, recorded accident decreases by 30% compared to 0 to .60 m. wide shoulder. And 20%o compared with a .90 to 1.20 meters wide shoulder.
It appears that, the above difference in accident potentials may not justifiz higher standard, particularly, when traffic volume is low. A driver's instinct when overtaking or allowing other cars to overtake or meting oncoming vehicles is to look at the surface width of the highway, and see the kind of surface where to position his car. Originally, the total surface width of the roadway was only 4.50 meters, but due to the increased number of vehicles using the roadway, the width was adjusted to 4.80 to 5.40 meters. Lately, the width of the road was standardized to 3.00 m. for first class paved one lane highway, and now 3.60 meters wide surface was adopted standard for freeways and other major traf30
t
fic
roadways, although tlere are strong demand further from 3.60 to 4.20 meters.
to
increase
it
For Two Lane Rural Highways, a 7.20 meters wide surface is required for safe clearance between commercial vehicles and is recornmended for main highways. For Collector Roadway, 6.00 meters wide surface is acceptable only for low volume trafFrc including few trucks traveling thereon.
For Local Rural Roadway, the minimum surface width is 4.80 meters for a 30 km / hr. design speed.
For Urbair Roadway, the minimum design width is 3.60 meters although 3.00 meters is allowed where space is limited. Where there are heavy meetings or overtaking between cars and trucks, air disturbances sometimes cause side collision between ing vehicles when sweryed within or out of their lanes. Motorists are requesting for wider lanes. Rounded 2:1 cut alope in deep cut
FIGURE 2-1 CROSS SECTION OF ryPICAL TWO LANE HIGHWAYS
FTGURE
2-2 MULT|-LANE HTGHWAYS AND FREEWAYS (HALF
SECTTON)
3l
Deg the Highway
Elements of Roads and Highways
I
100
2.50
3.25
13.00
3.25
2.54
Widening 0.20
0.15
0.15
0.20
L-
t I
!r...F-.?F Vr. < 100 Km / hr. Four 3.50 m. Lanes - 2.50 m. Stop Lanes
StoD lane
stop ranJ Shoulder
1.00
Medran
Travelway
I
Travelway
Shouldel
Roadway 33.50
Yr.
12O
Km / hr. or Vr < 100 km/hr. with 13 m. Median - 2.50 m. Stop Lanes
Vr.
Vr.
>
100 Km /
hr.
<
60 Km / hr. Four 3.00 m.
Lanes
-
250 Stop Lanes
2.50 Stop Lanes
Vr. < 100 Km /
hr.
Two - 3.50 m. Lanes 2.00 m. Stop lenes
23.50
Vr
<
100 Km / hr. 2.50 Stop Lanes
Vr. < 80 Km,/ hr. Two - 3.00 m. Laner 2.00 m. Stop lanes
22.O0
Vr.
< 60 Km /
FIGURE
32
Lr-
23
hr.
2.50 Stop Lanes
FIGURE
DIVIDEO HIGHWAYS
33
2-4 UNDIVIDED HIGHWAYS
t
Elements of Roads and Highways
2-5 Road Shoulder
Deg the Highway
Policy on Geometric Design Recommended that:
Road shoulder or verge is defined as that portion of the roadway between the edge of the traffic lane and the edge of the ditch, gutter, curb or side slope. AASHTO requires that its us-
l.
able pavement width shall be strong enough to vehicles.
2.
Importance of Road Shoulder
3.
1. 2.
Road shoulder serves as a place for vehicles to stop when disabled or for some other purpc,ses. Road shoulder considerably reduces road accidents. -l'he road capacity is decreased and accident opporrunity increases if the shoulder is too narrow or omitted in the
4. 5.
meters wide is much preferred. When the design hour volume
6.
For Urban Arterial Road, similar shoulder without curb
design.
3.
Shoulder should be continuous along the full length of the roadway. It also adds structural strength to the road pavement.
4.
Shouldlr increases the horizontal sight distance
on curves. It reduces accident potential when vehicle stop during emergencies.
Most of the road shoulders in rural areas are unpaved having a width of 60 to 120 centimeters wide either earth filled or graveled surface that during rainy days, drivers are hesitant to occupy. The Uniform Traffic Control Device Manual provides that:
Outside shoulder should be paved for at least 3.00 or 3.60 meters wide if tnrck volume is more than 250 in the design hour (ADT). The recommended width of left (median) shoulder is 1.20 to 2.40 meters with at ldast 1.20 msters paved. If there are 6 or more lanes, the median shoulder should be 3.00 meters wide or 3.60 metbrs if truck volume in the desrgn hour exceeds 250. For arterials with ADT less than 400 the usable shoulder width is fixed at 1.20 meters minimum, although 2.40
ADT exceeds 400, the usable minimum shoulder width is 2"40 meters although 3.60 meters is recommended.
is suggested unless needed for proposed drainage. The width of median shoulder on four lanes divided arterials is fixed at 90 centimeters as minimum. 8. For six or more lanes, 2.40 to 3.00 meters shoulder width is recommended. 9. For Rural Collectors Roadway, 60 centimeters wide graded shoulder is required for ADT's less than 400" 10. For ADT's over 2000. 2.40 meters wide shoulder is rec-
7.
ommended.
TABLE 2.3 WIDTH OFROADWAY X'ORUNDIVIDED HTGHWAY Total Trave
" All inter-town or city highways shall
provided with edge line and may be used on other classes of roads."
A
be
continuous narrow white line strip at the edge of the roadway that separates the shoulder, serves as guide to drivers during bad weather and poor visibilrty conditions. The white strips tend the driver to stay in the traffrc lane and the vehicles seldom infringe on the shoulder. )4
Shoulder Width
Roadway Width
of
Refcrence
100-80-60-40
14.00 m. 12.00 m.
3.25
20.50
3.25
18.50
60-40
7.00 m. 7.00 m.
2.75
12.50
2.00 2.7s 2.00
I1.00 10.70
2.75
11.50
1.50
9.00
100-80-60-40 80-60-40 100-80-60-40 80-60-40 80-60-40 80-60-40
6.70 m. 6.7C m.
6.00 m. 6.00 m.
12.20
35
Deg the Highway
r\lements of Roads and Highways
ONLY WITH STOP . LANE 15 Widening
Travelway
Stop
Lane
2.50
m.
or2.25 or 2.00m. shoulder 3.25 m. or 3.30 m.
or 2.75
Stop Lane 2.50 or2.25 or 2.00
nan
0.50
m.
RoundinO 1.00
S
stope or Ditch Stop Lanes 2.50 a( 2.25 ot 2.OO
Turfed
3.00 2.0O
l/4 to
to
Wall
3.00
1/16
UNDER STRUCTURE
Natural Soil 1.20
WITH STOP LANE AND GUARDRAILS
lq
f ravelway
5%
Stop Lane 2.50. 2.25 or 2.00
I
7% 0.75
Shoulder 3.25 , 3.00 or 2.75
Concrete
0.75 ON STRUCTURE
Covered gutter
Lane 2.50, 2.25 or 2.00
FIGURE
2{
FIGURE
STRAIGHT ALIGfTIMENT SHOULDER DETAIL WITH STOP I.ANE
24
STRAIGHT ALTGNMENT SHOULDER DETATL WITH STOP
LAilE AND GUARDRAIL
Elements of Roads and Highways
Deg the Highway NO STOP LANE, FOOTPATH OR GUARDRAILS ( NO PEDESTRIAN ALLOWED)
UNDER STRUCTURE
Shoulder 2.00, 1.50 or
1-00
WITH STOP LANE USED AS CYCLE PATH AND FOOTPATH
ON STRUCTURE Stop Lane / cycle path 2.5O or 2.25 ot 2.OO
UNDER STRUCTURE
A=
Stop Lane / cycle path 2.50, 2.25 ar 2.OO
Stop Lane / cycle path / footpath 2.5a, 2.25 ot 2.oO
A=
1.50 ifvr > 60Km/hr. 1.25 if Vr S 60 Km /hr.
Under Structure
0.50
Shoulder 2.00.1.50 -
if
1.00 shouldef
1
Stop Lane/ cycle path
?.50. 2.25
FIGURE
38
ot
2.OO
2-7 STRAIGHT ALIGNMENT SHOULDER DETAIL WITH STOP LANE USED AS CYCLE PATH AtlD FOOTPATH
ON STRUCTURE
FIGURE
2€
NO STOP LANE, I,IO FOOTPATH, I{O GUARDRAILS SHOULDER
39
I
Deg the Highway
Elements of Roads and Highways FOOTPATH ONLY
I.IT{SIDE SHOULDER
Footpath 1.25
- 2.00 -
1.75
-
1.50
Paved stop
if e<4%
if e<5%
if e>4% S=e if e>5% S=e
STRUCTURE 2. OUTSIDE SHOULDER
WITH FOOTPATH ANO GUARDRAILS
Footpath 75 - .50 - or .50
if
1.00 shoulder
UNDER STRUCTURE A = 1.50 if Vr > 60 km/ hr. A = 1.25 if Vr.l 60 km/ hr.
Shouldcr 3.00 or 2.50
FIGURE
2€
SHOULDER DETAIL FOOTPATI{ ONLY
FIGURE 2-10 ALIGIIIMENT ltrl CURVE SHOULDER OETATL
Elements of Roads and Highways Considering the above recommendations, Width is defined as "extendingfrom the edge of the surfacing to the point where shoulder slope intersect the side slope. " The Urban colleclor road usually has no shoulder, instead, parking lanes of 2.40 me' ters or preferably 3.00 meters wide with gutters are specified.
Deg the Highway These types
of cross sections allow the inner lane to acit is flatter than the outer
commodate high speed traffic because lanes.
On a very wide street, the parabolic crown surface makes the centerline almost flat unless gutters are sufficiently deep enough to convey water. A combination of uniform slope with parabolic curve is used instead of ttre parabolic sections.
2-6 The Cross Slope The cross slope is provided in all tangent sections of the roadway. Slope usually falls in both directions from the ce,lrterline of the uro lane highway except where super elevation of
Slope 1% to 2%
curyes directs all water towards the inside.
For high type pavemen! the crown or slope is often Iyo tD 2o/o. However, steqter slopes are strongly recommended because rain water, flow away more rapidly reducing the water thickness on the road pavement. A cross slope in one direction of multi lane hrghways makes driving comfortable, but with heavy rainfall, the water depth increases on the roadwqy.
FIGURE
2.12 HIGH TYPE PAVEMENT CROSS SLOP€
i
Center Line
FIGURE 2.13 PARABOLIC PAVEMENT SECTION
FIGURE 2.1 1 PAVED AND GRAVEL SHOULDER CROSS SLOPE
The paved shoulder cross slope ranges from3o/ota 6% although 4Yo is the most cornmon. For a gravel shoulder, 4%to 60/o slope is satisfactory and 7o/o slope is effective drainage for turf (grass) surfaces.
42
2-7 Cut or Fill
Slope
Eadh fill of normal height is safe on a slope of I:2 ratios. Meaning, the first number represents the horizontal distance while the second number is the vertical distance. 43
Elements of Roads and Highw*ys
Deg the Highway 2. 3.
EARTHFILL OF NORMAL HEIGHT 1: 2 RATIO
FIGURE
CUTS THROUGH ORDINARY UNDISTURBED EARTH 1:1 RATIO
2.14
FIGURE 2.15
Slope of cuts through an ordinary undisturbed earthfill remain in place with a ratio of 1:1 slope. On the otlrer hand, rock cuts could be as steep as l:2 and sometimes 1:4 proven to be stable. Receirtly, slopes had been geirerally lowered for safer operations and to facilitate plant growth. Plants reduced erosion and decreases maintenance costs.
Advantages of Flat Side or Back Slope
l. 2. 3.
With back slope of 3:l or even flatter, cars could be directed to back into the road and will come to stop or continue down the slope with no risk of over turning. Flat fill slopes are visible from the vehicles at full extent grirng the roadway safer appearance. With visible slope for being low and fla! vehicles could be positioned or parked closer to the edge, and on two lane roadway facilities parkmg would be farttrer from the opposlng traffic.
Recommended Policy on Geometric Design
1.
The 6:l slope ratio could be adopted on embankment than 1.20 meters high, and 4:l ratio on a higher fill.
less
The 2:1 slope is allowed to heights greater than 6.00 m. Cut slope should not be steeper than 2:l ratio except on solid rock or special kind of soil.
VISIBLE FLAT SLOPE
ROCK CUTS RATIO FROM 1:2 ro 1:4
FIGURE 2-16 ROCKCUT RATIO FROM 1:2 OR 1:4
The AASHTO policy stipulated that where cut or fill slopes intersect the original ground surface, cross section must be rounded to blend the slope with the natural ground surface. When the side slope requires e,nrbankrnent with suitable retaintng urall, any of the following materials could be used dependrqg uponthe natural conditions.
l. Fland placed stones. 2. Cerre,nt nrbbles masonry. 3. Concrete blocks. 4. Conventional reinforced concrete. 5. T or counter forted designs. 6. Cribs assembled fromtimber. 7. Precast concrete. 8. Metal elements.
,,./,
Deg the HighwaY
Elements of Roads and HighwaYs
9. Tied back piling. 10. Earth reinforced with metal or plastic bands' 2-8 Number of Lanes The number of lanes in a segment of the highway is determined from tJre estimated traffic volume for the design year (AADT) and highway lane capacity at expected level of service. AASFilO policies accept a dually divided 16 lanes roadway with four lanes in each direction for an inner freeway and four more lanes in each direction on the outside. There are some instances where a reversible lane is located at the center of freeways with unbalanced heavy traffic flow.
Curved median with 1.20 to 1.80 meters width serves as partition - separation of opposite traffic control devices.
10.
The width of a traversable median should be wide enough to prevent vehicles running out of control from
l.
The 15 to 24 meters distance between landed edges is favored, but specific value is not-stipulated.
12. Cross slope of the median should not be greater than 6:1
butpreferably l0:1. 13. Dense planting ofrose hedges serves as safety crash barriers.
For Narrow Median, there are four means of reducing cross median accidents:
tages:
l.
It is an effective means of reducing
2.
flicts, and accident between opposing streams of traffic. The Median offers refuge between opposing traffic stream ofcross traffic, and pedestrian could traverse each
7.
9.
I
Recently, median in various forms, becomes absolute requrrement for highways because, it offers the following advan-
6.
Medians with 6 to 18 meters wide allow drivers to cross each roadway separately. A 4.20 to 6.60 meters median width provides protection for turning vehicles'
reaching the opposite traffic.
2-9 Highway Median
3. 4. 5.
8.
1. 2. 3. 4.
headlight glares, con-
strearn at separate maneuvers. Median provides available space for left tum lanes. It makes turning of vehicles smooth and safe operation.
Provide Provide Provide Provide
detemng devices. non-traversable energy absorbing barriers' non-traversable rigid barriers. G.M. barriers.
Deterring Devices. - Two sets of double strip painted on the existing pavement, raised diagonal bars, low curbing and
Where space and cost permit, wide median is highly recommended. For rural sections of freeway, the 18 to 27
shallow ditches.
Non-Traversable Energy Absorbing Devices. The line chain link fence I meter high ed by steel post augmented by cables at the bottom and midpoint. Non-traversable rigid barriers are metal guard rail.
msters wide median is being adopted. The Policy on Geometric Design states that, 3.00 to 9.00 meters median width is appropriate in suburban or mountainous situations.
For rural and urban arterials, 18.00 meters median or wider is preferred because it allows the use of independent profiles and at the same time minimizes cross over
G.M. Barriers. A high non-mountain sloped face concrete barriers called New Jersey. It is cast or extruded in place or precast in section and set in position by crane.
accident.
47
46 _t
Deg the Highway
Elements of Roads and Highways
.20 Widening
Widening h = .02 to.04
Vr.
120 km /
hr. or eventually Vr. 100 km.l hr.
Vr. <1(X) kmlhr.
Turf or stabilization 5.60
Vr. < 100 km I hr.
5
D
___r---*
r-*t 1.00 |
I
Vr.
]
I
ll T_l
I
stabilization 1.80
Turf oi stabilization
.20 S
S'
|.-l
Stabilization 1.80
|
> 80 km / hr.
Vr. 3 00 km I hr. Vr. < 100 km I hr. FIGURE
2.I7
MEDIATTI
UNDER STRUCTURE FIGURE
48
2-t8 STRAIGIIT ALIGNMENT MEDlAltl lltl CURREilT
SECTION
49
Deg the Highway
Elements of Roads and Highways
--fi V
O1
ol dl
6, ol
J
ov@
:-
^qo Noo
9': @aio
3*3 ooo
r
€oY
I
E
09'e ol 00 e
I I
I
T
o
z s ul
=
Medlan > 3.00 meters
FIGURE
50
2.I9
MEDIAN ON STRUCTURES
F]GURE
2.20 MEDIAfII APPROACH
5l
1 Elements of Roads and Highways
Deg the llighway
{
BARRIER CURB
5
12.5
lN'ul,o tll
a=z.s/
I
I .7
ot rut zt
5l zl
10
ol FI
ffil q, zl
'l
10 I
20
ll \---t-r 'll?
Stope 30:20
(
I
repForls I I I
FIGURE 2-
22 MOUNTABLE CURB
2-10 The Grade Line Grade line is defined as the longitudinal profile of the highway as a measure how the centerline of the highway rises and
FIGURE 2.2,I DECELERATION LANES A]iIO II{SERTION LAiIES
fall.
Deg the Highway
Elements of Roads and Highways \o
!c
cil
The grade line appears on a profile taken along the road It is a series of straight lines connected by parabolic vertical curves to which straight grades are tangent.
o d
centerline.
F]
p
oo
=9o\.o\o
o E]
s z
€
€C-F-\On
1.
c{oo
Fl
o\
(h
o
I *o
In laying the grade line, the designer must consider the following:
2.
oo
90\€c-\o
q)
o
l&
t-
C-
F-
\O
3.
ral
rr
a FI o 4 trl
j
E
tn
"l
z
oo
&
ti
u)
=9a€ O\€l"-\O
.2 €F-\or
a
xtsl
Fl
Undesirable native soil should be provided with suffi-
5.
cient covering. Grade line elevations along the river or stream, erned by the expected level of water flood.
is gov-
q)
o
nssS
V)
&n -d
6
E
$cnco(a
! a.l
F]
\o
u)
\o
ao
B frl
rat !f
!? Fl Xg H,O o-
'tr9 9? q> ,R6 v5 og
>:()
r4
=o. tuz cf)
xg 54
drainage purposes.
4.
q
oo
X
tr tr
fte grade line must be considered balanced excavation against embankrnents to get the minimum overall cost. In flat are4 the grade line is set almost parallel to the ground surface but sufficiently above the ground for
2-11 Vertical Curve Over Crest
r-\O\Or
E
j
main consideration. In mountainous areas,
x
E A E
Where earthwork is minimal and consistently meeting sigtrt distances in relation to grade line, economy is one
E
$$38hpi
I
U)
All vertical curves should not be shorter than the established minimum over crests. This is govemed by the sight distance requirements but sometimes a case of riding, may demand longer curves than the sight distance. Some designers prefer no vertical curye to be shorter than 300 meters. AASHTO 5t'ggested that the minimum curve lengtb varies with the design speed in meters distance equals to 8 times the velocity in kilometers per hour.
" The vertical distance from the intersecfion ofthe straight grade line to the curve is equal to one eight ofthe product oJthe algebraic dffirence in grades and the length of the curve in stations. This is called the maximum correction. TIte rate at which the curve departs vertically from both tangent grade line 55
Elements of Roads and Highways
Deg the Highway
is proportional to the square of the horizontal distance from the end of the curve. The correction at any intermediate point is obtained by:
l. Z.
Multiplyrng the maximum correction by the square of the horizontal distance between the near end of the curve and the point. Divide this product by the square of one half the length
2-13 Stopping Sight Distance The stopping sight distance is defined as the longest disof an object 15 centimeters (6") above the road surface where the design height of the driver's eye abovc the pavement is 105 centimeters. tance that a driver could see the top
ofthe curve.
2-12 Right of Way Acquisition of land for the right of way is very costly. Based on experience from the past, highway agency now consider it a good practice to acquire right of way wide enough to sufficiently provide for the ultimate expected development. A successful freeway and expressway operations, closes the roadway from direct access to ading property and some 1o-
cal roads or streets. If local traffic and land use are to be opened, it must be served by service roads originally planned as part of the main freeway. Frontage road shall be permitted m enter coruresfing cross streets only at a distance of at least 100 meters for rural road and 50 meters f,or urban conditions.
of
Frontagc No Frontage Road
Road
2
60
45
4
68
53
Lanes
6 8
Source:
83
Rcstricted No Normal with
Frontace Rd.
FIGURE 2-23 MEASURING STOPPING SIGHT DISTANCE
Stopping Distance is Made-up of Two Elements
l.
The distance traveled after the obstruction or object is seen and before the driver applies the brakes. The second distance is consumed while the driver applies brakes for the vehicle to stop. The distance covered could be expressed by the following formula:
URBAN
RURAL
width
Object 15 cm. above the pavement
Z.
TABLE 2-5 MINIMTM RIGHT OF WAY WIDTHS FOR RI]RAL AND URBAN F'RDEWAYS AT GRADE IN METER Number
1.05 m. eye level
Normal No
d: tm/s
Rd
Frontacc Rd. F
Breakingdistance:
60
4l 5l
89
53
68
59
96
60
d: (m/s)2 19.6 f
A Policy on Geometric Design
Where 56
d : (m/s)2 2 gmf
:
m,/s
-
Initial speed, in meter per second 57
Elements of Roads and Highways
Deg the Highway
t = Detection,
recognition, decision and response initiation ( brake reaction time ) Acceleration of gravity, 9.80 meters per second squared Coefficient of friction between the tire and pavement.
gm =
f=
2-14 The ing Sight Distance
The above formula assumes that the highway level is flat. If the car is traveling uphill, the braking distance is decreased, and for downhill, braking distance is increased. 'lhe braking distance on slope is expressed by the following formula: Braking distance (m)
d = (.m/ s )2
g=
/
a/o
100
2{
Specd
Break Reaction
for Time Dstance
Km/ph Condition
Sec.
Mctcr
-
30 45 60
30-32 40-50
2.5
22-24
2.5
55-60
2.5
3l-33 4044
L:
:
4=
length required ofvertical curve specified sight distance algebraic difference in grades expressed in perceirt
75
65-75
90
80-90
48-55 57-66
inc Sicht Di Cocf.
100
85-95
2.5 2.5 2.5
105
90-100
2.5
&77
110
90-ll0
2.5
67-83
120
95-120
2.5
71.88
0.27
A Policy
6t-71
on Gcomctric Dcsign
of
Friction 0.40 0.35 0.32 0.30 0.29 0.29 0.28 0.28
Source:
Computed m€tcr
3r.8-35.8
Rounded for Design (rn.)
36-38 60-60
53.4-58.8 80.1-94.2 I12.8-138.3
112-142
r50.2-t90.2
I 57-195
t65.0-217.2 183.9-252.0 200.1-283.0 222.3-324.9
165-2t7
82-97
181.255
202-285 225-330
FIGURE 2-
24 MEASURING ING SIGHT DISTANCE
The design of two lane highway of ing over crests is generally practical only cn flat grades because the longer vertical curves are required to provide ing sight than stopping sight distance.
F = (m/s)i 9.8 Rm
58
L
Ii'INIMUM STOPPING SIGHT DISTANCE WET ROAD
Dcsign Assumed Specd
than
A
S
Uphill grade is positive ( + ) Downhill grade is negative ( - ) TABLE
L : 25 - 943 where S is greater
where S is less than L L is lurgth in meters 943
Longitudinal slope of tlre roadway or Grade
,
L : AS2
1e.8(f+g)
Where:
The ing sight distance is the longest distance that a driver can see the top of an oncoming vehicle where the driver's eye level is 1.05 mgters above the pavement surface. The relationship between the ing sight distance, the algebraic difference in grades, and the length ofvertical curve is represented by the following equations:
Se
Elements of Roads and Highways
Where:
Deg the Highway
s) : Meter per second Rm : Radius in mster Se = Super elevation (slope ratio) rise
(m /
per second
The maximum coefficient of side friction on dry pavement as determlned by curve tests ranges between 0.4 and 0.5 value with normal pavemsnt and smooth tires is about 0.35 at 75 kilometers per hour. TABLE 2.7 AASHTO MIMMUM ING SIGI{T DISTAI{CE FON DESIGN
T}f TWO-I.ANE I{IGIfl$AYS Minimum ing
invite accident. Similarly, deg circular curves of differem radius from end to end or compounded curve is not a good practice, unless suitable transitions between them are provided. To have a short tangent between two curves is also a poor practice. A long flat curve is acceptable at all times. It is pieas-
ing to look at, with less probability of future obsolescence. Alignment should be provided with tangent because there are drivers who hesitate to on curyes. A short curve appears like kinks. A long flat curve is preferred for small changis in direction.
2-L6 Circular Curves
Ovcrtaking Vehicle
Km/hr. 35
35
48
243
50 65
42
58 70
327
80
65
82
552
5s0
95
75
9l
&2
u0
100
80
96
693
690
110
86
l0:.
747
740
t20
90
105
780
135
95
ll0
780 822
))
244 320 440
,i'11
820
TABLE 2-8 AASHTO RECOMMENDED MAXIMUM COEFFICIENT OF SIDE FRICTION Design Spced Km/hr.
48
Cocflicient of Friction
.16
ll3 .10
A vehicle traveling in curved road is subject to centrifugal force. This force is balanced by equal and opposite forces developed through the super elevation and side frictions. However, neither the side friction on the super elevation, could overcome nor exceed the maximum control and limit on the sharpness of the curves with a prescribed design speed. The sharpness of a curve is dependent on its radius. Sharpness is expressed in of the curve degrees, and the degrees of curve is inversely proportional with the radius.
Formula: D =
5.729.58
=
5.129.58
Radius
Rrdi* D
129 .08
2-15 Road Alignment
Where: D = degree of curve and the radius Degree of curve SI : 0.328 D Solution using the above formula will give
following results: Road alignment should be consistent. An abrupt change from flat to sharp curve and long tangents followed by sharp curve should be avoided because it will onlv create hazard and 60
The degree of curve is expressed either by the Arc definitions or the Chord definitions.
6l
Elements of Roads and Highways
Deg the Highway
l.
TABLE 2-9 DEGREE OF CT]RVES
of
Rndirs Meter
30' lo 00' 20 00'
3A9r.7s
00
Decree of Curvc 60 00'
291.06
00' 00'
t't4.63
100
1,146.38 873.19
Radius
200
2.
per elevation.
87.32
Arc Definitions - The degree of curve is the central angle subtended by a 30 meters arc ofthe curve. Chord Definitions - The degree of curve is the central angle subtended by 50 meters chord. Radius
=
50 Sine % D
TABLE 2.10 SHARPEST PERMISSIBLE HORIZONTAL CT]RVES FOR GIVEN DESIGN SPEED AND SI]PER ELEVATION MaximumPermissible Degree of Curve D, or Minimum Radius Design Speed
Km/hr. Super
Elev. 0.04
0.10
Condition for use Dcsirable for down arterials
35 50 65 80 91 t13 .t7
.16
.15
.t4
.13
6 291
3.7s 466
.12
D
45
19
l0
Rm
39
92
175
Max for Rural
D
58
8.25
5.25
3.5
Rm
30
25 70
13.25
highway and
132
198
333
499
For design speed of 50 kilometers per hour, the normal cross slope is l'- 21' or even flatter curves. For a 120 kilometers per hour design speed road, the nofmal cross slope is 0'- 15' or flatter curves without su-
121
ln each of this solution, the total side friction 0.04 for an adverse cross slope of 0.02.
2-17 Super Elevation -,Runoff Curved sections of roadways are usually super elevated. Provisions for gradual changes from one point to the other should be considered. The centerline of each individual roadway at profile grade is maintained while raising the outer edge and lowering the inner edge to attain the desired super elevation. It is done by raising-up the outside edge of the pavement with relation to the centerline until the outer half of the cross section is flat. Then, the outer edge is raised until the cross section is straight. Finally, the e,lrtire cross section is rotated as a whole until firll super elevation is reached.
.ll
2.25 776
suburban frccway
Sourcc: A Policy on Gcometric Design
The maximum allowed super elevation rate before was 0.12 but now it is 0.10 except on low volume gravel roads. The Policy on Geometric Design recommend that : 62
is less than
Lane surface
FIGURE 2-25 SUPER ELEVATION OF CURVES
Deg the Highway
Elements of Roads and Highways TABLE 2.1I SUGGESTED MII{IMI.]M LENGTII OF SIJPER ELEVATION RI]NOFF F'OR2-LANE A3.60 METERS LANE
LENGTH OF RUNOFF FORDESIGN SPEED in Meter Super clevation Rate Km./hr. .02 .04 .06 .08 .10
35
9.0 18.0 28.5 37 .5 48.0
95
50
10.5 2r.0 33.0 43.5 54.0
12.0 15.0 25.5 28.5 37.5 43.5 5l .0 57 .0 63.0 72.0
16.5 33.0 48.0 @.5 8r.0
ll5
18.0 36.0 54.0 72.0 90.0
130
19.5
39.0 60.0 79 5
AASHTO recornmended the run off leirgth to vary both with the super elwation rate and the design spee4 but with minimum sst for appearance and comfort to riders. A roadway that lies in a cut, where the grade line is nearly flat, may create sag by lowering its inner edge. This may not drain surface water.
It is advisable to make the super elevation by raising the outer edge elevated tvrice ttre usual distance. Where the alignment is of tangent connected by a circular curve, super elevation is started on a tange,ft before tlrc curve is reached and full super elwation is accomplished at a distance beyond the point of curve. It is therefore recornmended that 600A ta 80% of the runoffbe on a tangent. For wider roadway, the length give,n on Table 2-9 should be
Four lanes, individual value increased by 50% Six lanes, individual value increased by 100%
A provision for a wider roadway is necessary on sharp curve for two lanes pavement under the following reasons:
l. 2. 3. 4.
To force the drivers to shy away from the pavernent edge. To increase the effective transverse vehicle width for nontracking of front and rear wheels. To give additional width due to the slanted position of the front wheel to the roadway center line. For a7.20 msters wide roadway, an additional width of 30 centimeters is necessary on an'open curve highway.
99.0
Sourcc: A Policy on Geometric Design
increased as follows:
2-t8 Widening of Curves
Reverse circular curves are seldom used on modern highways, but reverse cuwes that are provided with proper length easemsnts between them are acceptable. If no easement curve is allotted, curves on opposite directions should be separated by tangent several meters long. There are roads with compound curves that change abruptly
from one sharpness to another. Where the radii of the compound curves are Jifferent, sudden change confuse the drivers and in turn they shift position within the lane and sometimes veer out of it. For this reason, compound circular curve of different radii is considered as poor design. recommends that the radius of the flatter curve for rural highways should never be more than 50olo greater than
AASFilO
that of the sharper one. For urban intersection, this easement curve is considered which introduces the changes in radius gradually. Super elevation changes along this transition section.
2-19 Island An island is a defined area bstwesn traffic lanes for control of vehicle movement and for pedestrian refuge. Within an intersection, median is considered an island. This definition makes evident that an island is no single physical type. 65
_ T
Elements of Roads and Highways
Deg the Highway
It may range from an area delineated by barrier curb to a pavement area marked by paint. On at-grade intersection in which traffic is directed into definite paths by island is termed as Channelized Intersections.
Island is included in the design of intersections for the following purposes:
l. 2. 3. 4.
Separation of vehicular flows. Separation of conflicts. Reduction in excessive pavement areas.
The angle between intersecting streams of traffic can be smooth
6.
Prohibited turns may be prevented
and favorable
Reduction of traffic and indications of proper use of intersections.
5
Mlf
Arrangement to favor a promineirt turning movemerf. Location of traffic control devices.
To confine vehicles in a definite location without proper route for vehicles and pedestrian, everyone's action could not be predicted by others and these are usually the main cause of confrsion which lead to accidents. By
charurelization, the angle
streams
or route between intersecting
of traffic can be smooth and favorable. Drivers are
commanded to merge into moving traffic strearns at flat angle and right speed being controlled over vehicles approaching an
A ItH'l
Speed of vehicles controlled over approaching intersections
T
Funneling vehicles into narrowing opening prevent oveftaking and ing conflict area
intersection.
When cross traffic meets at flat angle, head on collision cotrld be more serious. A right angle at 75'to 105" is most favorable glving the driver that opportunity to assess or calculate the position and speed of oncoming vehicles. By channelization, funneling is also effective in preventing overtaking and ing in conflict areas. A well studied super elevation is an imporfant adjunct to channelization that regulates the vehicle speed and:
1.
Prohibited turns are prevented.
r*
-ll/t( II tl
Ir Refuge provided for turning
vehicles
Drivers commanded to merge into moving trafftc streams.
FIGURE 2- 26 GENERAL TYPES AND SHAPES OF AN ISLAND
-
Elements of Roads and Highways
3.
By channelization, refuge may be provided for turning or
4.
The drivers has to face only one decision at a time,
crossing velucles and pedestrians. hence, conflicts can be avoided.
5. It provides location
for the traffic control devices like
Deg the Highway Under this type, weaving and merging movements are separated. It also provide an opporfunity to speed adjustment clear of the fieeway. When Freeway meets Freeway where traffic movement is heavy, interchange is provided with directional left tum in all four quadrants.
signs, signals and refuge for pedestrians.
2-20 Types of Interchange The tlpes and form of freeway intercharrge requires selection of the conformation that is best suited to a particular situation and demand. The functions of freeway interchanges are:
l. 2
To provide separation befween two or more traffic arteries. To facilitate the easy transfer of vehicles from one entry to the olher or betwesn local roadway and the freeway"
The simplest and low cost form of interchange is the diamond type. It is recornmended where the freeway crosses nonfreeway arterial. The cloverleaf type interchange is recommended for fi'eeway and arterial intersections. Intersecting arterjes are separated and free of intersections.
Y - Type lnterchanges
Objections to the Cloverleaf Interchange Design
l. It requires large area ofland. 2. At higher design speed, more time is consumed just to traverse the longer loops.
3.
Vehicles making left turn execute 270' iLdtrt. turn and travel greater distance beooming very unpleasant and
4.
Vehicles leaving the curve loop in one quadrant weave those entering the adjacent loop from the through road-
hazardous due to the sharp curyes and steep grades.
way.
Alternative cloverleaf design with collector distributor road recommended for one or two through street if the cost of added land paving and structures can be justified.
is
6b
FIGURE 2.27 TYPES OF FREEWAY INTERCHANGES
tt9
Elements of Roads and Highways
Deg the Highway
Directional Interchanges
Partial Cloverleal
Through freeway with rotary flyover with roundabout A Pollry on G.omctlic Dosign
FIGURE 2.28 TYPES OF FREEWAY INTERCHANGES
'to
FIGURE 2-29 CHANNELIZED INTERCT-.IANGES
71
I I
Deg the Highway
Elements of Roads and HighwaYs
l. 2. 3.
4" Four Level
For right angle intersections with linle trafhc. fie use of street sigh is more than sufficient. For Y intersection or other related conformation where vehicles meet at unfavorable angles may require channelization.
'lhe flared design will involve the following: a. Widening the entering trafEc lane to allow deceleration of tbe car and clear of through traffic. b. Widening the leaving lanes to provide acceleratiotr and merging fiom the traffic streams. Intersections must accornmodate large trucks. and the radius of all curves must be suffrcient enough to accommodate them.
A careful traffic count and projected future improvement must precede the design of all critical sections. Based from the dat.e gathered on trafftc count, the lane capacitl'could be determined including the ttumber of lanes to be constructed.
llll
)f_* Three Level
____)[ _
Three Level
FIGURE 2-30 FULLY DIRECTIONAL INTERCHANGES
whgre land is very expensive' Figure (a) Roadway at four levels is appropna]9 of roadways required to level 3, ln to**on (b) an
7-21 Highway Intersection at Grade at grade' highways except freeways have intersections connecting roads' lntersection area is considered part of every oocur' mov€ment turning In this area'all crossing and
Flared - T
Unchannelized - T
a)N I t
rHREE LEG rNrERSEcrroNs
| \
T- with Turning RoadwaY
All
FIGURE
2.31
INTERCHANGE AT GRADE
73
72
Elements of Roads and HighwaYs
Y - with Turning RoadwaYs
Deg the Highway
A
THREE LEG INTERSECTIONS
l\
AN* -=N T' \ /
ll /F- .' channerized-Y
Flared Type FOUR LEG INTERSECTIONS
Four leg channelized type intersections
tl /\
-AN-Four leg channelized type intersections
Rotary intersections roundabout
FIGURE 2-32 INTERSECTIONS AT GRADE
M
ulti-leg Intersections
FIGURE 2-33 INTERSECTIONS AT GRADE
Elements of Roads and l{ighways
Deg the Highway
2-22 Freeway Entrance and Lxit
TABLE 2.12 SAMPLING OF MINIMUM FOR FREEWAY ON AIID OFF TIIE RAMPS
The overall effectiveness of the individual freeway systems is governed by the flow characteristics of vehicles, and the driver's behavior near on and offthe channel.
On Ramp or OffRamp Design Speed Km/hr. Freeway
20
Speed
30
40
L = Length of Ramps in Meter
Km/hr. OnRamp
:
PARALLEL ENTRANCE
177
5l
450
303
174
ll5 147 170
95 t29 153
tO2 129
228 350
321
ll0
4't7
130 159 185
80 i,
150 273 400
95
Off
Ramps 80 95 110
189
48
68
Source: A Policy on Geometric Design
FIGURE 2-
34
DESIGN OF FREEWAY INTRANCES
,t' single lane on ramp vehicle flows into the outer continumg freeway lane. The design is either a taper blending into the through lane or an auxiliary lane parallel to the through lane. In either case, sufficient length is required to allow the vehicles to accelerate and merge into the ongolng vehicle stream at a speed near that of the freeway.
Vehicles leaving the freeway need distance to accelerate and clear of the flow of ongoing traffic. In situation where one lane could not meet the traffrc demand, two lane exits is necessary. In that situation, an auxiliary lane must be added to the freeway at least 800 meters before the point of exit. Even with one lane exit, an auxiliary lane is necessary for it reduces confusion and congestions. 76
5l
PARALLEL TYPE FREEWAY EXIT
TAPER TYPE FREEWAY EXIT
FIGURE 2-35 DESIGN OF FREEWAY EXIT
72
102
Elements of Roads and HighwaYs
2-23 Railroad
CTIAPTE
- Highway Separation
The main question asked on a railroad and highway separation is: 'Iilhere one is to go over- the railroad or the highway? If the highway is to go over the railroad, the structure itself is lighter *a *" highway load is much smaller than the railroad loads. With regards to the vertical clearance height, the railroad requires a minimum of 7.00 meters as against 4.80 meters clear distance above the highwaY. If the highway goes under the railroad, special provision is required for the removal of rainwater that falls wrthrn the^oppoiirrg area. If the ground water is high in the vicinity of the Lror.ittg, the roadway must be sealed against leakage and be made heavy enough to prevent from floating.
2-24 Bicycle Lane
soIL 3-1 Soil and its Origin From the earliest civilization up to the present time, soil is
the most important material that influenced mankind in his struggle for survival. The material where man grows his food, build his homes, roads, and ultimately his final destination.
The soil referred to in this study, is the materiat used to build with, or on that acts in combination with other forces of nature to make structures and land forms. The material classified under the field of Geotechnics.
Bicycle use is now becoming popular due to energy crises and traific problems. It requires separate road for the riders that is entirely separate from the vehicular traffic. The design speed is 20 to 30 kilometers per hoor for flat section. The width is 2.00 meters minimum for a 2-way travel. The grade of the lane is 57o maximum on short distances.
Soil may be defined as the accumulation of unconsolidated sediments and deposits of solid particles as a result of the rntegration of rocks. On the other hand rocks may be defined as natural aggregate of minerals connected by strong bonding of attractive forces classified as consolidated materials. Scientifically, most of the non-organic materials idelrtified as soil has originated from rocks as the parent material. Rock tlpes are classified into three major classes in accordance with their own origln or method of formations:
l. Igneous rock. 2. Sedimentary rock. 3. Metamorphic rock Igneous Rock is the result from the cooling and hardening of molten rock called magma ttrat has originated from deep
within the earth. The rapid cooling of molten magma called lava which was blown up by volcano solidifies into small crystal and 78
79
Blements of Roads and Highways Residual soil Transported soil
fine interlocking texture. The molten lavas that rapidly cooled on the earth surface are volcanic rock qpes called basalts, rhyolites and andesites. The molten rocks that were trapped deep below the surface of the earth, cooled slowly, and the mineral components forms into large interlocking crystals and coarse textured rocks classified as plutonic types of which,
Residual Soil or Sedimentary Soil is fomred from the weathering of rocks or accumulation of organic materials remained at the location of their origin. Weathenng plocess may
granite is the most common.
be attributed to ntechanical, chemical or solutictn weathering.
Sedimentary Rocks are formed from accumulated deposits of soil particles or remains of certain organisms that have harden by pressrue or cemsnt€d by materials. Sedimentary rocks include limestone and dolostone, shale, conglomerate and breccia. Shales are formed from deposited clay and silt particles. Sandstone is predominantly quartz cernented together with mostly silica, but sometimes with calcium carbonate of iron compounds. Conglomerate and breccia are similar to sandstone.
due
possesses
Mechanical weathering, refers to physical disintegration to effects of wind, rain, running water or tectonic forces
(earth quake).
Chemical and solution ieuthering, is deconrposition of rock due to chemical reactions that occur as a result of exposure to atmosphere, temperafure changes, reaction with water or other materials. l,ikewise. climate, topograplry, d'einage and vegetative cover have great rnfluences on the chemical or solution weathering process.
Metamorphic Rocks are rocks resulted from metamorphism due to changes in ternperature, pressure and plastic flow, changing the originai rock structure and mineral composition of the rock. Under tlds processes, limestone is change to marble, sandstone to quartzite, shale to slate or phylite
Transported Soils are frose rnaterials transported from their place of origin. Transportation may result due to the ef-
The process of rock changing to soil and soil to rock and alteration of rocks are continues and occurring simultaneously. The process of changes or alterations takes place over a long period of time, and there is no sst sequence wherein changes occtu.
The major categories of soils are gravel, send, silt and clay. Gravel and sand are universally known ts coarse grain soil be' cause of their individual particles that are large enough to distinguish without magnification. On the other hand, silt and clay are considered x fne grain soil because of their tiny particles.
There are numerous t]?es of rocks to elrumerate, but tlre construction industry and Engineer's concemed are not gsnerally afflueirt with the name of rocks but with their properties, specially in-place properties such as hardness, strength, durability, soundness and all other properties needed to build on or built wittr.
Particles larger than gravel are commonly referred to as cobbles or boulders. Thus, it is apparent that particles size alone is the basis of classifying sand, gravel, cobbles and boulders. On the other hand, fined grain soil is classified as either silt or clay not on the basis of particle size but on the plasticity or nonplasti city of the materials.
Categories of Soil
Over a var''lng range of moisture content, clay soil is plastic and sticky. When dried, possesses strong resistance to crushing. Silt soil has little or no plasticity and when dried has very little
Soil can be divided into two categories, namely:
fects of gravity, wind, water, glaciers of human
activif.
3-2 Types of Soil
8l
' f
Soil
Elements of Roads and llighways
l. Gravel Coarse sand 3. Fine sand
or no strength at all. If small amount of moist silt sample is shaken on the palm of the hand, water will appear on the surface of the sample but disappear when shaking stops. This phenomenon is called dilatancy. Sand mixed wittr silt is classified as silty sand, whereas, silt and clay mixture with mostly clay is called silty clay.
3-3 Characteristics of Soil Soil consists largely of minerals formed by disintegration or deconiposition of rocks. Disintegration or decomposition into soil may be caused by the action of water or other natural forces like temperature change, or by plant or animal life.
2.
4. Siltgrain 5. Clay 6. Colloidal claY
Gravel consist of rock fragments more or less rounded by water action or abrasion classified according to the following types:
a) b)
Quartz is the hardest of common rock forming mineral' IY'ell Rounded Pebbles and Boulders - those that undergone long period of wear that become almost quartz.
c)
Slightly Worm Gravel is rough and angular including other materials or rocks like granite, schist, basalt or limestone.
Soil contains humus and organic acids resulted from decay of vegetatron. All soils contain water, either free or absorbed in varying contents. Soil in most cases, are blend or mixture of particles of many sizes, shapes, and parsnt rock materials making its behavior very difficultto predict.
It is very common to encounter five to ten or more distinct types of soil along a kilometer of road. Change of soil types at frequent intervals has become a rule rather than exemption. Behavior of soil mass could be determined based on the characteristics of individual soil particles such as:
1.
2. 3.
Grain size Grain shape Surface texture and electrical surface charges, resulted from chemical composition and molecular structures.
Regardless of the differences in grain sizes as classified, tlre colrlrnon objective is to establish a basis for relating the particle size to soil behavior.
The General Characteristic and Classification cles are enumerated as follows: 82
of
soil
parti-
Fine Sand has particles that are more angular than the coarse and fine sand particles.
Coarse Sand is usually rounded like gravel with which
it
is
found and generally contains the same materials.
Silt Sand is similar to fine sand with the same mineral composition. They are found as rock flour in glacial moraines" It could be produced by chemical decay. Occasionally, silt contains:
1. 2 3.
Pumice Loess
Materials foreign to the associated sand.
The presence of silt in fine soil could be detected by its grittiness when small amount is bitten between the teeth.
Clay is plate like, scale like, or rod like in shape as a result of chemical weathering. Because of their smaller sizes, its performance is influenced by moisture and surface chemistry'
Colloidal clay is a finer clay particle that remains
pended in water and does not settle under the force of gravity'
sus-
Soil Elements of Roads and Matenials
If like soils occur under
like conditions of rnaterials" the
Coarse Grain Materials. F'or most purposes, coarse grain materials are considered satisfactory construction material. On the other hand, silty soil will create problerns in areas where the ground has moisture movement due to capillary action. Soil that contains clay would be troublesome, making the design and construction more difficult. As a rule of thumb, soil with clay
slope and weathering, the soil patterns or simiiar landfomrs, are also developed. The surface dramage patterns and erosion characteristics, together with the color of the goil, reflected the kinds and nature of the soil. Ridges with parallel axis may also reflect wind blown sand and silts.
should not be used clq:ser tn the roadway surfaces.
The texture classification of soil depending on the grain size distributron is classified irito three groups, namely: (a) sand (b) silt and (c) clay.
Irnpnrtant Graim Shape Characteristics
l. 2. 3. 4.
Rounded particles exlracted from the stream that has undergone wsar, are considered strong materials.
Flat and flaky particles that were not subjected to wear, are weak and variable that is not suitable for various used. Angular or roughly cubical shape particles produced from crushing strong and tough rocks, increases the resistance
of soil mass to deformation when subjected to load, due to individually interlocking grains. Generally, the rounded particle has the tendency to roll over each other when subjected to load.
3-4 Classification for Soils Pedology is the science of soils. It is the basis for pedological classification under the principle that: "like soil are developed on like slope when lilce materials are weathered in like " Regardless of geograplucal locations where slopes "fashion. and climate are the same, the depth and nature of soil mantle, are also similar.
Under the pedological classifications, soils that were produced in like fashion from the same parent rock, is assumed to possess siniilar engineering properties, that also requires similar enginlering trcatment. The number of sample to be subjected for sampling could be less than what is usually required. The test results serves as check on pedological classification contrary to the other classification methods that rely mostly on physical tests with little attention to pedological information. 84
GRADE Coarse Sand Fine sand Silty
SIZE OF PARTICLES (MM 2.00 0.25 0.25 0.05 0.05 0.005 Smaller than 0.005
-
-
FIGURE 3-1 TEXTURAL CLASSIFICATION FOR SUBGRADE $OIL OF SAND AND SMALLHR SIZES
Soil
Elements of Roads and Highways The posrtir:ns of every point inside the triangle represent the sieve analysis of soil in particular grading. After determining the grain size ofthe sample, charts is read as follows;
l. 2. 3.
2.
Sutrdivision of Snnd and Gravel Symbols
w
Spaces vertically upward startrng from zero at the bottom represent clay percentage.
GW SW
Spaces from left to right diagonally downward starting with zero at the left, represents silt. Spaces from right to left diagonally downward starting with zero at the right, represents sand.
Soil that is almost entirely a mixture of sand and silt are classified as loams. Every soil containing clay of less thmr 20o/o, is ctassified as loam with a prefix sandy or silty added to indicate which predominates. These will appear at the lower portion
C
for well graded, fairly clean materials fbr well graded gravel for well graded sand coarse materials with clay binder in combination GC and SC. poorly graded fairly clean material in combination GP and SP. coarse materials containing silts or rock
flour in combination GM and SM
3.
Fine grain soil (more than 50% ing No' 200 sieve)
4.
Fine grain soil grouped according to its liquid limit
of the chart
Soil containing 20 to 30 percent clay is called loam, with the term clay added to indicate the higher clay content. The name appears as loam classification in the chart. All other soil is designated as clay with prefixes of sandy, or silty to indicate the remainder of the materials.
Symbols
The Unified Soil Classification System, was introduced by the U.S. Anny Corps and the Bureau of Reclamations. Letters were used instead of numbers to designate the differerfi groups. The mechanical analysis and the liquid and plastic limit tests are the primary classification toois. The principal symbols and
For fine grain soil with liquid limit less than 50, low to medium compressibility in combination ML, CL and OL For fine grain soil with liquid limit greater than 50, high compressibility in combination MH and OH soil
soil designations are:
l.
Identification
For coarse grain soil - more than 50% relained on No. 200 sieves.
l\te lJnified Soil Classtfcation System recommended
sev-
eral ways for quick identification of fine grain portions of the soil, namely: For gravel or gravely soil For sand and sandy soil
l.
The sample is mixed with water to have a puttyJike consistency, then fonneci into pat and dried cornpletely 87
Elerments of Roads and l{ighways 2. 3.
5
6.
Soil
If the pat is hroken by the fingers and the dry strength is hrgh, plasticity of the sample rs considered high. If dry strenglh of the sample is high, then, it exhibits clay and colloid charactenstics If the sampie is a pat of fine silty sand, it rvill easily break in the finger. Fine sand will cause the pat to feel gritty on the fingers.and silts is smooth. Dilatancy or reaction to shaking is another way of classifuing the soil mortar. About one cubic inch of soil is rnixed with water and forrned into a pat of soft but ncrt sticky consistency. If the material is of fine sand, shaking and jotting ttre sample on the palm of the hand will bring water to the surface of the sample. Squeezing it between fingers causes the rnoisture to disappear. Silts react less cornpletely but clay does not.
TABLE
}I
3-5 Composition of Soil Soil deposit consists of solid particles and void spaces beparticles, either partially or completely filled with water. Void spaces not completely filled with water, are either filled with air or other gases. Therefore, soil deposits are composed of solid, liquid and gas
1y7esn
Engineers are interested to know the properties of soil deposit, specially, the strength and compressibility because they are necessary in determining the bearing capaclty and stabiltty of the foundation. Strength and compressibility of the soil is
directly related to:
l. 2. 3" 4.
Void ratio. Degree of saturation.
COMMON SIEVE TYPES AND F1ESH OPENINGS
Sisve Size
Designation No
U.S. Standard
Millimeter
Tyler Standard
Millimeter
Uritish Standard
Air=0
Millimeter
4
4.7N
8
2.362
10
1.651
20
0.833
40 60
o.u6
100
0.147
200
0.074
270
0"c)53
400
0.038
A Policy on Geometric Design
E .ol o
= G o F
Volume of Air = Va
AIR
Weight of tl
Source:
Soil density weight per unit volume. Water content of the soil.
Volume of voids = Vv
Weight of
water * l rw
Mass of
.?
o
water = Mw Weight of
solid
=
Ws
Mass of solid = Ms
t ,ffiIJ; ..:.
l,l'.,-u
o
'^;'.iiiTi ,.*. ,
(Soil) r.;
,;
F
Volume of Solid = Vs
iii,',,,,'it'iti ;i,ll
*'.;i-is$
FIGURE
o E
Volume of Water = Vw
WATER
ll
_'rld[3't*ffi
3.2 RELATIONSHIP BETWEEN VOLUME AND MASS WEIGHT
Relationship Between Mass Volume and Weight Volume From Figure 3-2,the total weight of the soil volume is:
l{ lJ
89
Soil
Elements of Roads and Highways Weight of the solid (Ws) + Weight of the water is equal to the Total weiglrt (Wt) or Ws
2.60 tD 2.75.
Similarly; for measurement of the mass'
The Unit Weight of Soil U could be Expressed as:
Ms + Mw: Total mass Ms*Mw=Mt
Wet unit weight Uwet
The total volume (Vt) = volume of solid
*
volume of voids.
Vt: Vs+(Vw+Va) = Volume of solid + Volume of voids Vt: Vs+Vv The relationship between the weight and volume of any materials will be:
Vg Dw
Where:
w- Weight of ttre material (solid, liquid or gas) V= G:
Uw=
M= Dw=
Dry unit weight Udry
Volume ocoupied bythe material. Specific gravity of the material. Unit weight of water at temperature stated (in most soil work, Uw = 62.4 pounds/ft3 9.80 dynes/cm3;or 9.81 kN/m3 regardless of temperature) Mass ofthe materials Density of water (l gm/cm3 or L95 slugs/ft3)
= ![s ( p/ft3, kN/-t) Vt
For soil density:
=
Wet destiny Dwet
ry[t_(
kghf,gm/cm3 )
Vt Dry density Ddry
= Ms (kglm3, grlcm) Vt
+l gm/cm3 = 62.4 polnds per cubic ft. The weight of one cnt' of water = 980 dynes The weight of one
VgUw
M:
= Wt ( p/ft3, LN*t ) Vt
Therefore, the total volume of the soil sample of the butk includes the solid and liquid air or gas. The volume of water and air is called-volume of vcids, Thus:
while Mass and Volume
The specific gravity of most commonly occurring rock or soil or soil materials is between 2.30 and 3.10.
* The specific gravity of soil solids lies within the range of
+Ww : Wt
W:
t
ft
of
water =
62-4lbs-
By definition, water content W is the ratio of tlre weight of water in soil volume to the weight of soil solids, or of the mass of water in a soil to the mass of solids. Thus:
W w o/o Ww Ws
Mw Ms
= Wwx 100% or Mwx
Ws
100%
Ms
Water content in Percer(age Weight of water Weight of dry soil Mass of water Mass of solid
Elements of Roads and l{ighways Soil
The relationship of water content and the r,veight r:f dry soil to the total wet weight of the soil volume should be:
Wt = Since:
Ws
p o/o
=
p%o
:
+Ww
Ww : (wolo)Ws r00%
By substitution: Wt
=
Ws + ( W% ) Ws 100%
Ws
e
O:IU*%J rc0%
ws= Ms=
Wt
Mt
t. q%
and the water content is known from a represertative sample.
The Void Ratio and Porosity in relation with the s,clid and void volume follows:
p%'.
The degree of saturation S, indicates the portion of the void in a soil material that is filled with water. The degree of saturation is expressed in percentage.
S7o=Vw
w
x 100%
Full saturation or 1007o saturation means that all voids are filled with liquid. Since
Vt = Vs * Vv and e = Vv
vt:vs*evs = (l+e)
Vs or;
Ys_= Vt
Vv
The Void Ratio is expressed in decimal number, and the Porosity P is conventionally expressed in percentage. Thus:
100%
spaces
Volume ofvoids Volume of solid
Vs
92
100%
1-
1+e
The weight of dry soil mass could be found easily with these equations when the weight of a large soil mass sample
e:
=
P%
pYo: e
t.iE%
rc0%
e :
100%
100%
100%
Simrlarll
Vv x Vt
And the relationship between void ratio and porosity is:
By Factonng:
Wt =
Volume of voids x l00o/o Total Volume
l+e
Example -1 One cubic foot of soil sample weighing 130 lbs. was taken from a test pit. The entire sample is thoroughly dried and finally weighted 120 lbs. Solve for the water content, wet unit
weight, and the dry unit weight. 93
Elements of Roads and Highways
q
.g
=lr
q tt
EEE
E (0
F
I
(v)
€N
.E
x-x 6.=6
E
:ro.9
xx odtx EE9 ooE t@
6
E (o
x6
x6.=
(a)
EI N
(\
do ar ZY
rl(,
=a 6P
*6 IJ
trJ
ze o(,
;) ;FAD {x
9F a> ut
cr)
x6
1r)
x 6 E tf,) (t
f
oo !to
L Z.o
+
8R
G
.9
o 6 (t
o
EEE
e*** zzz =
o
ilz EE
x6 E @o
xxx 66G
o
gE
t!
EE
AE Eto oct \b=
:9
#: i Etz' .g r
sg E.g
g!
E I!
E
lo
I
bo
Ha Eo c9
$iEe EEfE
;.E 5 Pd )(/)o
o
130
-
120
:
l0
lbs.
120lbs.
l30lbs/cu. ft.
gs3 !E3. S€E
:W:130: vt 1.0
Dry unit weight
Uory
= Ws =120
= l20lbs/cu.ft
Vt Watercontent wo/o
=E EeE
i6
water: Ww
Uwet
sFeI
gB
E s
: Weight of dry soil Ws : Weight of
Wstunitweight
66
E
x0t
Solution
i€+
*EE 9.9€
fo-
oQ, -> dF
}3
= 1.0 cu. ft.
E
E6
cD )c
FIGURE
Total volume of sample
E€
E Escr .^€ 6 oc, .l=0
E-
E
s
sEL E!d eE(' EoO oooc :'
.c
XX 6G
fa; €
:=g I o-9
o
ootrt lf,c.t-
arl
e t!
E9
EE
I
('?
F.
EE
tft -o .cl
-EE =-.9
.96
xx 6ad
iX .=G
(t
5gb
!t c 6 o
o
c') (\l
rEt € Et
-c EO J;ro iEo .D=
o
la)
o
trl Fl !e
E$fl
xx o6 EE
E
N
EE
F* Eg E.E 1
.lt g
6.=x FE6 o ttf
E tt)
:j
EEf
o
x6
c\l
,L
o o
c,)
(o
(J
F (,
o
EE
|rt
.a
CD
EEE € ON
E c) .E
I I
o
*
@
q
q,E
()P -g
-xx .=66
ut
5?
o
.E
E
F
o
v,
o
G'
CD
trl
5B
.9
BEE o@
iltrl
F
x
Soil
rr-iP
#Ei 8.gb
a.E 6
E3E
E 3a E g€ 5aL
= Ww x l00Yo = l0llbs. xI}}Yo
Ws
= Example
-
1.0
120lbs.
8.3%
2
Compute for the wet density, dry unit weighg void ratio, water content and the degree of saturation from a sample of moist soil with mass weight of 20 kg that occgpies a total volume of .008 cu. m. and .006 ou. m volume qf solid. The sample is dried in oven and weighted 18 kg. The specific gravity of the soil solid is 2.60.
Soil
Elements of Roads and Highways Example - 3
sample of wet soil has a mass
A 200 cubic centimeters
of
300 grams when 100% saturated. The mass was wheridried. Determine the dry density, dry unit weight, water content, void ratio, and specific gravity'
FIGURE
180 grams
34 trd = 3oo gm
Vt =
Solution
=
Wetdensity: Dwet Dry unit
H=ffi:2,500kg1m3
= Ws:Msq
U&y
:
200
Vt
FIGURE 3-5
Vt Solution
l8 kg. ( 9.81 kN/m3
). =
22.072kN/m3
Dry densitY: DdrY
.008m3
=
Ms
Vt Water content: w%o
=
=
20
-
Mrryx 100% Ms 18
l8 Void ratio:
180
x 100%o = I1.l%o
Dryunit weight: Udry
gn/cm3
= 56.Zlbs/cu ft
:
Water content: w % LMw) Ms
0.33
.006
300
S% : Wqs : 1l.l x2.60 =
e
0.90 gm/cm3
= ( 0'90gm/cm')6fats4'1)
e =Yv = .008 - .006
=
200 gm
Vs
Degree of saturation:
sm
0.33
sq-
x
100%
180 sm. 180 gm.
X
100%
87o/o
66.60Vo 97
Elements of Roads and Highways Volume of water.
Vw
=
Mw
gn*
= 3-Q0gn.--l-8ggn = l2o cm3
Soil Solution
l.
Since sample is saturated, all voids are filled with water.
(1.0X1.0 gmlcm') 2. Void
ratio: e = Vv = 0.40, but Vv
120 cm3 is the value of voids because 100% sao.ration means that, all voids are filled with water.
Therefore:
Voiume of soil solids:
Vs = Vt-Vv Vs : 200 cm'- l20cm'
= Voidratio:
-
:
e: Vv =f20 = 1.5 Vs 80
Vs*eVs 1.0 + 0.40
(1.0)
.Ww
:
80q = VsDw ( 80cm3X 1.Ogfi/cm3)
1.40
:
VwUw
):162'24lbs
(0.40)(62.4)
=
24.96lbs.
2.25
4
From which:
Laboratory test result showed that the v-oid ratio of a saturated soil sample is 0.40. The specific gruvity of soil solid is 2.50. Find the wet unit weight of the soil and its water content.
+Ww
=
Wt =
1d/5
wr =
187.20lbs.
162.24 + 24.96
Thus:
Wet unit weight:
I-Jwet
=
: oh Water content: w
Vs = 1.0
Wt
vt
= 187.2
133.7
= Ww x
1.40
pcf 100%
Ws
Assumed
= FIGURE 3-6
98
=
1"0( 2 60 X 62.4Pcf
Mg_.
= Example
Vt: :
Ws = VsgsUw
80 cm3
Specrfic gravity: gs :
and Vs are not known so. it is assumed that Vs = l 0
Vs
24.96Ibs. x 100% 162.24lbs.
=
75o/o
99
Soil Elements of Roads and Highways For soil above the water table but 10004 saturated. we have:
To relate a value given in grams per cubic centimeter (i.e. density) to pound per cubic foot (i.e. unit weight), multiply by 62.4 gn/cm3 = 62.4lbs/ft3.
Usuh
soil =
Usub
soil
=
Usat soil - Uw
Usatsoil- 62.4lbs./ft3
Submerged Soil
Exarnple - 5
For under water condition, the soil solid is buoyed up by pressrrs of the sugounding body of water. Therefore, the weight of srrbmerged suil, become lighter compared with the soil al-.ove water" Thus, the effective soil weight becomes the mit '*'eight when weighed rmder water. The weight of water in the voids of soil is zero when submerged, because all voids werc assumed to be filled with water, and the weight of the snlid is reduced bythe weight of water displaced.
One cubic foot undisturbed soil from a test pit, weighs 100 pounds net weight. The dry weiglrt of the sample is 80 lbs. What will be the effective unit weight of the soil if it is submerged below the ground water level when the specific gravity
Therefore. the submerged weight is equal to the soil weight above the water minus the weight of water displaced. Thus,
Wsub
=
Vs gs Uw
-
is 2.601
Solution U sub soil
:
Vs
(by faaoring)
Usub
soil
= &us = Vtotal
Vs Uw (es -1)
Vs(l+e)
= gg l Uw I *e
i00
= ll2
(100 pcO
=
50 lb/ft3
= Wf- : 80lbs. gs Uw 2.60(62.4) : 80 : Agff
Vv: Vt-Vs
For easy computation, the submerged weight is % the wst soil above the water table, except the soil containing significant decomposed vegetation or organic materials. U sub soil
1/z
162.24
Since the unit weight is the total weight divided by the total Volume, we have:
Usub-soil
=
Using the accurate formula, we have:
Vs gw Uw
= Vs Uw (gs - gw) = Vs Uw (gs-l)
YzlJwet
U wet soil (approximately)
=
1.0
-.49 = .5lff
e=Vv =.51 = I.04 Vs .49 Usub = ( gs - l) Uw = Q.6A-I\ rc2.4) (l + e) (l + 1.04) = 48.94lbs/cu. ft. or submerged weight: Wsub
=
=
(.49X62.4>(260-1)
Vs Uw (gs -
:
l)
48.921bs/cu. ft. t01
Elements of Roads and HighwaYs
Soil
or for the volume of one cubic foot:
For coarse grain soil, the higher the density or unit weight, the stronger the sheer strength, and the lesser the tendency to settlement by compression. Determination of In Place Density or Unit Weight is made on borrow pit soils to detennine the shrinkage volume or swell result as the soil is transported and compacted at the fill location. The standard practice is to test the in-place density of the soil after dumprng cn site, to determine whether, compaction is
Usub: Wsub : 48.92lbs./ft'
vt
1.0 ft3
3-6 Soit Reaction to DensitY The property of soil that contains larger amount of fines, are influenced by mixture railter than by any other factor. Soil that is strong enough with ing capability under one set of moisture is changed. Records revealed that an increase of l% moisture content on granular layers increase damages to pavernent by a factor of 700. Definitely, ';oils that are used as sub grade is subject to moisture changes. Density of soil is its mass per unit volume' It is sometimes expressed as "Wet Weight" or the total weight including water. The air volume in the soil substantially decreases as soil particles become dense when compacted. The most importarf ionsideration in pavement work is, to decrease the moisture (water) content ofthe coarse grain soil.
To decrease the moisture content, is to increase the density to improve the physical properties of the soil. High cornpaction of the sub-grade and base of the coarse grain materials is an accepted practice. On the other hand, over compaction of clay with high affinity of water, may result to big trouble unless confined by superimposed load like the weight of an over laying fill. This type of materials when compacted will mix on water and expand resulting to road surface failure'
necessary.
.
The modern equipment used for making in place density and unit weight test, is a nuclear apparatus. Through controlled use of n rclear materials, gamma iays (photons) are emitted into the tested soil. The photons collide wilh electrons in the soil materials. Some are being scattered and others were being absorbed. The quantity of, photons reaching a detection device relates to the soil density to determine the water content of the soil. A Newton etnitting device and detector is used.
3-8 Relative Densify For granular soil, the sheer strengtl and resistance to compression are related to the density of the soil. Higher strength and resistance to compression are developed by the soil when it is dense, or compact condition ftugh denstty), than when it is in
a loose condition (low density). ln a dense condition, the soil void ratio is low and high on loose condition. Relative densrty is expressed in percentage, thus:
Dro/o= emax-eo 3-7 In-Place Density and Unit Weight ln-place density, refers to the volumetric weiglrt expressed in pound per cubic foot, or kilo Newton per cubic meter, or *"gu gra-t per cubic meter of soil in the undisturbed condition or conipacted fill. The density of water is one rnega gram per cubic miter (l mglrn3) or 1.000,000 gm/m'. la2
:100%o
emrx-emin. Where: e max e
- Void ratio of the soil in its loosest
condition.
min - Void ratio of the soil in its densest condition. eo
- Void ratio of the soil in its natural conditioned or conditions in question. 103
Elenrents of Roads and Highways
Soil
so
Vv
03
Vs
.06
Dr%o=
:
0..5
emax-90 xl00% ernax*emin.
Loosestcondition Intermediatecondition Void ratio
=e
rru
Void ratio = eo
Densestcondition Void ratio = e 66
0.90
- 050 :80%
0.90
-
0.40
Dry unit weight of soil: FIGURE
}7
RELATIVE CONDITION OF A GRANULAR SOIL
Udry
In temrs of dry unit weight, the relative riensity is:
Dr 9/"
Wherc
:
Dul __Dq*
I -_l_
x
l00Yo
Dud
i
Dul = Dry unit weight in its loosest
= Do = Dud
condition. in its Dry unit weight densest condition Dry unit weight in its natural condition or condition in question.
TABLE
}3
-
6
of undisturbed fine sand .09 cubic foot, l0 lbs. dry weight with specific gravity (gs) of 2.60 was tested at the maximum density of 0.40 and minimum densrty with void ratio
A
sample
R.EPRESENTATTVE VALUES OF R.ET.ATTVE DENSITY
Dcscriptive
Relativc
Condition
Density %
Loose
Less
Medium Densc Dense
Example
lbs/ft3
Referring to table 3-4, the soil is dense.
l-l Do
: Ws = ,10lbs = lll wt .09
Very Dense
than 35
35-65 65-85 More than 85
Typical Rangc of Unit Wei LbV cu. ft. KN/m3 Less
than 90
90-
ilo
ll0 - 130 More than 130
than 14 14-17 17 -20
Less
More than 20
Source: Esscntials of Soil Mechanics and Foundation by David E. Mc Carthy
of 0.90. Find the relative density of the undisturbed sample. Solution
: Ws = 101b. = .06 ft3 gs Uw (2.60)(62.4) Vv =, Vt - Vs = .09 - .06 - .03ft3 Vs
104 105
Soil Test and SurveY Under the Stoke's Law, "The rate of settlement of solid through a given liquid or gas is proportional to the square of the diameters of the solid." The AASHTO method as specified is called Hydrometer Test AASHTO designation T-88.
CTIAPTER
SOIL TEST AI\D SURVEY
+l
Hydrometer Test
1. Samplc of the material ing
Test for Particle Size
Different soil has dif;lere,lrt charactenstics affecting the perof each individual soil by mois[re conteirt and density. There are sweral kinds of physrcal tests that have been dweloped to measure soil performance issued and recommeirded by AASHTO and ASTM. (See Transportation Materials Part I and II Tests or hferim Tests Methods by AASHTO). formance
The Sieve Analysis is the process being used to de0ermine particle sizes of gravel and fine aggregates. A sample of the the material is thoroughly dried and shake,n through series of sieves rangrng from roarse to fine. The amount on each sieve is weighed and recorded. The AASHTO standard sieve sizes for soil aggregates are presented as follows:
Sieve No. in Inches
By Number Opening in millimeter
) l t/2
3t4
37.5
25.0
r9.0
9.50
4.7 5
l0
40
200
2.0 .425 .075
Source: AASHTO Desien:tlon T-27,1v192 and ASTM Desig. E-l I
Material finer than No. 200 sieve (.075 mm) is not feasible in d*ermining the particle sizes. Insrtead, these are determined by observing the rate at which the grain5 settle through liquid or gas. 106
thoroughly with water and dispersing agent that dissipate any electrolytic bonds in the sample that might cause fl occulation and accelerate settlement.
2. After 12 hours, the miirture is agitated rnaking all particles suspended in water.
3. The mixture is then placed in a graduated flask, allowing 4. 5.
6.
the solid to ssttle under the pull of gravity.
The bigger particles settle first, followed by the smaller then the smallest one. The specific gravity of the liquid decreases. The changes are recorded by special hydrometer and read at prescribed intervals. Change in specific gravlty is related to the grain size of the material by Stoke's law' Careful control of temperature and other possible variable is strictly observed to obtain satisfactory test results'
4-2 Test to Evaluate the Effect of Moisture
3/8 4
50
No.10 sieve is mixed
Consistency of the soil varies from semi solid tlren, to liquid if water contsnt is increased.
l.
to
plastic
The Liquid Limit Test The AASHTO designafion T-89 onliquid
limit signifies the
percentage of moisture at which the sample changes- by decreasing the water from liquid to plastic state. When the sample is wet than the liquid limi! a grooved sample of the soil in will flow when lightly juned 25 times' On the other
"hand, "opif the sample is jarred at the liquid limit water separates
107
Elements of Roads and Highways
the soil particles just wide enough to rerncrvs ttre soil
Soil Test and Survey mass
shearing strength. Several tests on each sample are required to reach the moisture content wherein the groove in the sample is required to close at exactly 25 blows.
2. The Plastic Limit Test AASHTA Designation I-90 signifies the percentage of moisture wherein the sample changes with lowering w€firess from plastic to semi-solid condition. At this stage, the soil mortar starts to crumble when rolled into threads l/8" diameter" Additional water will make the soil plastic, but sands are nonplastic material that its non-plastic limit cannot be daermined.
3. The Plastic Index Text AASHTO Dengnation T- 91 is defined as the numerical difits liquid limit and its plastic limit. It is also referred to as the percentage of dry weight. ln some cornbination, it measures: ference bstween
a) The fineness and shapes ofthe soilparncles. b) The interplay of the attractive forces tending to hold the
c) d)
clay mineral flakes together. The thickness and velocity ofthe water film and, The quantity and electrical charges ofttre cations.
For coarse grain soil or fine grain soil with few particles of clay of colloidal size, small increase of water above the plastic limit will cause particles separation, destroying the athactive forces that provide shearing strength. It simply means that the difference between the plastic limit and the liquid limit is small, so that the plastic index is also small. On the contrary, for a soil that is high in clay or colloids, more water will be required before the attractive forces are overcome, and the strength of the mass is destroyed. In this case, the plasticity index is numerically high.
Experienced road builders use the Plastic Index as one conselecting the materials for under pavement. A common base course materials specified, requires the plastic index not to exceed 6 while others insist on not greater than 3. Soils with high plasticity indices are much less acceptable for sub-grade in
trol in
base course.
4. The Shrinkage Test Shrinkage test measures the changes in volume and weight that occur as partly mixture of, soil and water (except sieve No. 40). Sample is dried from the near liquid limit to constant weight of 110'C. The results are stated in of shrinkage limit, volurnetric change, and lineal shrinkage.
Higher value of shrinkage factor showed tlrat the soil will give more trouble and problem. The volume of a certain soil increases when it absorbs water. Soils that are suitable for subgrade and base course are those that oqpand very little when moistened. And those that swell more are considered as poor materials. A common soil specimen requires volume change limit of lYo for base coarse materials.
5. Hand Feel Test Experienced soil Engineer employ the "hand feel test" to approximately predict the plasticity index of the soil. The test may include
a)
Thread toughness at moisture content approximating tlre plastic limit.
b) c)
The air-dried strength.
Dilatancy
Soil mortar possessing hrgh plastic index threads and high strength without dilatancy.
will produce tough
r08 109
Soil Test and Survey
Elements of R'oads and HighwaYs On the other hand, soils having low Plastic Index (PI) will react in an opposite manner. Skilled soil technician could on tJre basis of this iest predict the Plastic lndex with standard error of about lToPercent.
clean sand with some rocks and certain other materials are classified as non-plastic materials because they cannot be rolled into threads as required in determining the plastic limit'
weight ofsoil per cubic foot cannot be termined in particular instance.
The Main Variables in the Soil Proper are:
l.
of the soil. Arnass composed of entirely spheres of one size in the deirsest possible condition will contain 75To solid and 25Yo voids. The smaller the sphere in the mass tlie higher the perce,lrtage of the solid" hence, particle size distribution may greatly affect
of road materials
Non-plastic soils are excellent lvpe
2.
when properly confined under wearing course' A weli gr"AtA rock dust form hard durable surface when
3.
6. Sand Equivalent
Test
AASHTO Designation T-176 is for field determination of the presence of undesirable quantities of clay-like materials in soil. Aggregate mixture is based on the volume, rather than on weight. Thi sand equivale,lrt is the ratio between tlre height of the-sand column (laboratory experiment tesQ and the combined height of sand and expanded saturated clay expressed in perg" Higher values of sand equivalent indicate superior ma"*t terials. The allowable moving avelage value from the Califomia Specification is 21 for sub base, 3l for agglegate baseand- 4^5Sb for aggregates of various type asphalt condete and 76 for concrete sand.
4-3 Density Test of Soil TheDensityofsoilorweightpercubicfootvarieswiththe
peculiarities of the soil itself, the moisttlre conten! and the compacted device plus the method of their use. The standard
ll0
densrty.
wst and comPacted.
Clean sand displace easily under load and their use as fill or base course create problems, but they may have other desirable feature such as facilitating sub-surface drainage'
Specrfc Gravity of the soil particles that may vary from 2.0 to 3 .3 that is normally between 2 .5 and 2.8 .
2. Particle Size distribution
As a rule:
1.
fixe4 but should be de-
3
.
Grain Shap" of Soil Particles . Sharp angular particles will resist shifting from loose to a compacted state. Flalcy particles in soil will decrease its density because they are difficuhto compact.
4-4 Laboratory Test for Soil Densrty Test for density may be divided into two:
l. Laboratory test to set $andard for density. 2. Field test to measure the density of soil in-placed on tlre roadway.
Laboratory tests may be subdivided into three, according to the basis of compaction procedures.
l.
2. 3.
Statictest. Dynamic or impacttest. Tamping foot or kneading compactiontest.
Static Test is determining the marimum density of soil sample in the laboratory. A sample of about 5000 grams of soil containing a specified percentage of water is placed in a cylinder mold 6 inches &.ameter and 8 inches high.
lll
Elements of Roads and Highways
Soil Test and Survey
The sample is then compressed under a load of 2000 pounds per square inch applied at the speed of 0.05 inch per minute. When the maximum load is reached, it is held for a period of I minute and therl gfadually released from the known dry weight of the soil. The mold diamet€r and the height dry densrty of the sample are comprrted. Several samples are compressed to delineate the peak of the moishre density. This peak value repre-
circle. About 25%. of the specimen is covered in each application. Compaction is through lsteadtng action in contrast with
seirts the standard.
Dynamic or Impaa fesf. Samples of soils each containing a designated perce,ntage of water are conrpacted in layers into molds of specified size. The sample is compacted by applying a number of blows from a free falling hammer of prescribed dimension and weight with flat circular face. The peak of moishrre densrty value represents the standard density. The AASHTO tests may be apptied on ttrat portion of the soil which will No. 4 siwe or all that es '/t" sieve. TABLE
4.I DETAIIS OF DYNAMIC COMPACTION N AASHTO
TestDaails Diameter of Mold (inches) Height of Sample (indreO Number of Lifts Blows per Lift Weight of }lammer lbs. Diameter Diameter of compacting Surfacr (inches) Surface Free Free fall tdistance (inches) Volume, Volume, rnet in cubic ft.
'AASIITO Designation
.
4-5 Field Density Test of Soil in Place Field density test is the means of comparing the density with the laboratory results. The comparison is performed on tlre basis of relative cornpaction defined as follows: Relative Compac,tion
=
Drvwt. /cu ft. of soilinlMtwayStructure Dry wt./ cu. ft. of soil sarnple at optimum moisture contsnt corpacted in standard mannel.
Relative compaction is the only measure by which the acceptability of a complaed roadway strudurc is measured.
Field Density and Moisture Content by Sampling TEST
The manners of determining relative compaction by samphng are as follows:
California
Standard
**Modified AASI{TO
Irpact
l.
Obtain samples of the compacted materials to be tested at
4to6
4to6
2.86
5 cut to 4.58
l0-12
full depth. Find the wet and dry weight of the sample, therL deter-
25 to 56
5 crr to 4.58 5 25 to 56
2.
20
3.
5.5
10
10
2
2
2
3
t2 1/30 or l/13.33
l8 ll30
18
or1113.33
T-99 ** AASIITO Designation
)
Varies
4. 5.
T-180
Tamping Foot or Kneading Compact Test. Tlrcmaterial is
fed into a rotating mold and compacted by several repetitive loads applied through tamping shoe shaped like a sector of the
t12
the static pressure or impact test
mine its moishrre content. Det€rmine tlre volume of sample in the fill by finding the weight of materials requred to fill the space. From the dry weight of the sample and the volume that it occupies in the fill, find the dw weight per cubic foot.
Find the relative compaction of the soil in fill by dividing its dry weight per cubic foot by the laboratory standard densfy.
There are four factors that affect the accuracy ofrneasuring relative density, they are:
1.
Change in the soil itself.
l13
Elements of Roads and Highways
Soil Test and Survey
2. The sampling methods. 3. The accuracy of laboratorytesting for standard density. 4. The accuracy of testing field density.
Load of test specimen at 0.1 in piston penetratiol
CRB = Load carried by standard crushed rocks based on 0.1 inch piston penetration
4-6 The Strength Test Soil tests to determine the strength of soil is classified into:
l.
Test for load carrying capacify, rate, and arnount ofconsolidation in soils that zupport the foundation. (This is applica,ble to bridge foundation).
2.
Test to measure the ing power of disturbed soils as compacted under standard procedures.
STEP - 1 COMPACT BY STATIC PRESSURE OR BY IMPACT
STEP.2 GRAPHANDFIND MAXIMUM DENSITY
California Bearing Rrtio Method (CBR) The Caffirnia Bearing Ratio Method (CBR) combines a load deformation test performed in the laboratory with an empirical desrgn chart to determine the thickness of pavement base and other layers. The tests are briefly conducted as follows: STEP
t. The disturbed soil samples at different moisture conteirt are compacted in 3 layers by static loading or impact hammer into a cylinder mold 6 inches diameter by 8 inches high. The specime,n depth is about 5 inches. The 5.5 pounds hammer AASI{TO standard density test is
.3
FIGURE
SOAK IN WATER
STEP
-4
APPLY LOAD
4.1 LABORATORY PROCEDURES IN FINDING CBR OF SOIL
The HVEEM Stabilometer Method
used in the rmpact method.
)
The moishrre deirsrty curve is plotted. The sample with greatest dry dens4y is chosen.
3.
The specirnen in the mold is immersed in water for four days to allow saturation. Expansion of the specimen is recorded.
4.
A small piston of 3 inches diamster is forced into the confined specimen. Load deformation data is recorded. The California Bearing Ratio is computed as follows:
This method measures the horizontal pressure developed in a short cylinder sample loaded vertically on its end. Stabilometer Operating Procedures
l. 2.
:
Four different samples are prepared on a short cylinder about 4 inches diameter by 2 % inches high of different known moisfure contents. Compaction is done using tamping foot or kneading compactor.
Soil Test and Survey
Elements of Roads and llighways
?,.
Each compacted specimen inside the mold is compressed until water exudes from it and several electric circuits wired in parallel through the base plate of the exudation measuring devices. ,-i|lrar'. r.- ,t?l(fxmfF4|;!F
e :rittli
t Head oftesting machine Follower for ap,plying load to specimen Neddle valve Air chamber
ldanually operated screw lype pump
Stabilometer T'est After the expansion test, the specimen is enclosed in a flexible sleeve and placed inside the stabilometer. vertical pressure is applied sl.rvly at speed of 0.05 inch per minute until it reaches 160 psi. The developed horizontal pressure is reduced to 5 psi using the displacement pump. The tums of displace_ ment pump needed to bring the horizontal pressure to 100 psi is determined. This displacement procedure ls intended to measure the penetration of the flexible cliaphragm into the intersection of the sample.
Liguid under small initial pressure Diaphragm Plate of testing machine
Loading piston Load cell leads
Cell pressure inlet
Sample cap
FIGURE
+2
DIAGRAM OF THE HVEEM STABILOMETER
Displacem ent transducer
It
was found out after several tests that soils in underlying of about 300 psi. It appears that soaking did not produce a condition of certain fine grain materials. ln effec! the exudation pressure is a different means in determining the moisture contents of the soil on the roadway. Moisture content in stabilometer test samples is set to bracket the 300 psi. value on which design was based.
After exudation test while sample is still in the mold, it is tested for expansion pressrue. A perforated brass plate is placed on the sample and covered with water for 16-20 hours. Expansion during this period is prevEnted, and the pressrue that prevents it is measured. As mentioned earlier, soils that expanded due to the presence of water should be placed under sufficient weight of fill to prevent swelling.
ll6
-
Clamps for displacement transducer
paveme,nts exceeded moisture under pressure
Test for Expansion Pressure
Porous stone Sample membrane
Samplo
be Vacuum inlet
FIGURE
+3
Chamber
Vaouum saturation inlet
Displacement transducer inlet
SCHEMATIC DIAGRAM OF DYNAMIC MODULUS TESTS
The resistance value R of the soil is computed by the following formula:
R:100-
100
2.5Pv-l+l Ph
Soil Test and Survey
Elements of Roads and HighwaYs Where:
It
R = Resistance value : Vertical pressure (160 psi) D = Turns displacement reading
Pv
Ph
:
(aPProx. from 2 to 5) Horizontal pressure in psi at Pv
was found that the modulus of asphalt concrete ranges depending upon the temperature. For cernent treated base, from 500,000 to 3,000,000 psi.. For aggregate base and sub base from 10,000 to 50,000 psi., and for fine grain aggregate soil, 1,500 to 50,000 psi, depending upon the water conlent. ,** r;
from 100,000 to 1,000,000 psi,
of 160 psi
Loading piston
Tri-Axial Design Method
Bearing plate
This method is used by some agencies for compression tests (see AASHTO Designation T-234). In open system tri-axial test, lateral pressure is held constant releasing from the container as increased load causes the sample to expand lalerally.
Transducer yoke
Lead to reoorder
Reaction and displacement continuously recorded
Constant supply of pressure
Displacement tran6ducet
Screw clamps to fasten yoke to sample
FIGURE
One of 3 tie rods
Lead to recotder
&5
SCHFMATIC DIAGRAM OF DIAMETRICAL TEST
Nuclear Devices Test
lmpervious bearing plate
-
Rubber membrane PerVious disk Lucile cylinder
FIGURE
4'{
TRIAXIAL TEST
FIGURE
+4
TRI-AXIAL TEST
Dynamic Modulus Re-compacted or undisturbed samples are tested to determine the influence of temperature, degree of saturation, density, and age on the d)'namic response of pavement rnatorials'
Recently, Nuclear Devices for determining in-place densities and moisture contents are used. The gauge readings are easily converted to density and prevent moisture using calibration curves or microprocessors. The portable device is either the transmission, or bac:< scatter tlpe.
The transmission type measures density and moisture content for any depth up to 25 centimeters. The back scatter device is placed directly on top ofthe soil layer or slightly above it to provide an air gap between the instrument and soil surface. It measures density and moisture content to a depth of 3 to 4 inches. Nuclear device overcomes construction delay where samples could be taken while construction equipment is operating. The Nuclear device travels over the fill at about 4.5 kilometers per hour and continuously recording the density and mois' ture content"
Soil T"est and Survey
Elements of Roads and Highways Gamma photon delector
lnstrum ent
Soil surface Transinrtted photon Compton scattered Photon
Gamma Photon source
FIGURE
4.6 SCI.iEMATIC DIAGRAM OF NI"'CLEAR DEVICES TRANSMISSION TYPE
l. Identification of soil types from: geological and agricultural soil maps, aerial photographs, and other sources. lnvestigation of ground water conditions, exarnining existrng roadway cuts and other excavations. Review of the design and construction procedures, and present condition ofroads that traverse the area. 4. Soil exploration along the right of way using auger boring and test pile. Sampling should be at fiequent intervals to fix the boundaries ofeach soil types. 5. Test holes should extend to a significant depth below the sub-grade elevation with reconnmended minimum depth. 6. Tlie location, nature of the ground, origin of parent materials, landform and agricultural soil name, should be re2.
corded. Gamma photon detector
Garn rna photon
7.
so tfce
Soil surface
8. Path of gamma photons (compton scattering)
Frcu RE
+7
scH
EIriJf.pJl?i#f;N
uc LEAR DEV| c Es
4-7 Soil Survey The preliminary soil investigation is an integral part of highway reconnaissance and preliminary location survey. In fixing the position of the roadway, the following should be taken into s: Soil conditions. Directness of the route Topograph5'
4. fught of way. 5. Neighborhood disruption. 6. Environmental consideration
The earlv phase of soil survey is the collection c'f infbrmation gathered from the following.
Each soil layer is described according to thickness, fixhrre structure, organic content, relation contents and cementation. The depth of seepage zones of fiee water table and bedrocks are also recorded. The soil profile along the roadway centerline showing location or test hole range of soil profile characteristics for each district soil gpe is plotted.
Along with the first reconnaissance and preliminary location survey. The highway agencies make a detailed study of the following data.
l.
The vertical and horizontal location ofthe proposed con-
2.
Location and evaluation of suitable borrow and construction materials. Need for the type of sub-grade or embankment foundation treatnent and drainage" Need for special excavation and dewatering techniques. Development of detailed sub-surface investigations for specific structures. lnvestigation of slope stabilrty in both outs and embark-
3. 4. 5. 6.
struction.
mem.
Elements of Roads and llighways
CHAPTER
Refraction Seismic Method
A
geophysical method used for sub-surface exploration cdled refraction seismic method relies on the principle that, the speed of shock travelling through the earth surface varies, depending upon the kind of materials. Shock waves travel through light loose soils at approximately 180 meters per second, and 6,000 meter per second on dense and solid rock.
ROAD MATERIALS 5-1 Aggregates Aggregates intended for either Bituminous (asphalt) or Portland cement concrete pavement, should be of good quality in accordance with the requirements of AASHTO standard or Item -703 of the Department of Public Works and Highways specifi-
If the earth's
crust is of uniform material for some d"pth, these time intervals are proportional to the distance from the origin of explosion. If the surface layer is of harder denser material, the time interval to a distant point is shortsned. The shock waves travel beneath the denser material along its upper margin, and then returned to the recording instrument.
cations which generally provides that:
"The aggregates shall consist ofhard durable particles or fragments of crusheri stone, crushed slag, or crushed rock or natural gravel."
The records frrr the time of wave travel against the shooting distance, the number and thickness of the different underlying layers, including the depth to bedrock can be predicted. This test is usefrrl in determining the depth of the rock but could be deceivrng on roughly tilted stratified materials.
Aggregates to be classified as good quality, must undergo various test enumerated as follows:
l. 2. 3. 4. 5. 6.
The refraction method was developed for exploration of underground conditions of roadway cuts. The shock wave is obtained by striking a 6 inches square steel plate wrth 4 kilogmms sledged hammer. The test is done by applying direct cur-
rent to flow through the soil between two other supply electrodes placed immediately at the third points. The resistivity changes where depth is produced, recording the results at vari-
Test for strength. Test for soundness. Test for affinity and swell. Test for shape and texture. Test for resistance to polishing. Degradation test.
Test for strength
ous electrode spacmg.
The criterion for aggregate stength test is the Los Angeles Rattler Test (AASHTO T-96) briefly conducted as follows:
This method is somewhat reliable although sometimes it can not be totally depended on regarding the information as to the presence of solid rock. It is useful in area exploration when it is used to find localized sand and gravel deposits.
1.
t22
Rattler test is done in a hollow cylinder closed at both ends. The cylinder measures 70 centimeters inside diameter by 50 centimeters long provided with steel shelf projectrng radially inward 3 % inches mounted with its axis horizontally on stub shaft a:rd fastened at the ends. 123
-L
Elernents of Roads and Flig,hwars
Road Materials The cylinder is rotated 500 revolutions at speed of 30 to 33 rounds per minute. 3.
After testing, the sample is ed on to No.l2
or strip's-off from the aggregate, the pavement will disintegrate sieve.
it
are sst aside, the amount of loss is the difference between the original and final weight expressed in percent. Those that es through
The FFIWA recommended that aggregates for a
5.
dense
graded mixture shall have 50 or less coefficient of wear.
For open graded mixture, the requirernent is 40 or less. However, percentage may be set in cases where excellent asgregates are abundantly available.
under traffrc.
Another reaction of the pavement is to pit when aggregates are pulled-off caused by running wheels. In the event that pavement mixture swells, the interlock and friction between the particles are destroyed resulting to collapse of the pavement stabiltty.
l. Hydrophilic is the term used when the
Test for Soundness of materials to deterioration from the effect of action like freezing and thawing. The comrnon test for soundness is the application q'ith sodium or Soundness refers to the resistance
magnesium sulfate. (
See
AASFIIO T -104
2.
).
l. A sample of fine or coarse aggregate is dried, and then, 2. 3. 4.
immersed in a saturated solution of sodium or magnesium sulfate, followed by draining, and oven dryrng.
The application of liquid solutions will cause splitting, crumbling, cracking or flaking of the particles surface. The application is conducted in five immersion and dry-
particle sizes. The result is recorded as percentage loss. Some road agencies do not require soundness test for aggregate intended for asphalt pavement particularly in areas where temperature of the pavement does not fall below freezing point.
Strong and durable pavement must have binder that adhere or stick firmly to the aggregate particles. If the binder separates
means fear, or against,water. If an aggregate is hydrophilic, the chemical bond between the aggregates and water is much stronger than those between aggregates and asphalt. On the contrary, if the aggregate is hydrophobic, pinholes will develop on the asphalt and water penetrate the surf;ace until it reaches the aggregates.
3.
Such water aggregate interferences may develop at the sharp edge of crushed particles and in due time, water
will 4.
ing cycles.
After washing and drying, aggregate samples are exermined carefirlly and sieve to determrne. the changes in the
Test for Affinify and Swell
t24
aggregate has
affinity for water than asphalt. Meaning, they like water than asphalt in contrast to hydrophobic which greater
5.
destroy the aggregate and asphalt bond. Sometimes, the stripped asphalt flushes to the surface of the pavement making it slicky, and after stripping, fine aggregates that are susceptible to swelling will expand when moistened, then disrupt the pavement Structure. The funmersion compression test (AASIilO T-165) indirectly measure the tendency of aggregate to strip or swell under the effects of water. The stripping problem of aggregate has long been perennial problem, although, many experienced engineers knows which of the aggregates being used will or will not be affected.
Shape and Texture of Aggregates
A relatively rounded smooth aggregate particles like natural gravel is recommenJed for Portland cement concrete pavement 125
Elements of Roads and Highways because the mixture is workable. Meaning, easily managed and consolidated inside the forms.
2.
The angular or cubical shape and rough surface texture aggrcgate tras been proven excellent material for asphalt pavement because it has stronger interlocking action and well adherence of asphalt binder to the particles.
3.
A thin or elongated piece of dirt is considered undesirable material for either asphalt or concrste pavement.
4.
The AASHTO Standard Specifications for asphalt pavement aggregate has no specific stipulation as to the control ofthe shape or surface texhrre.
Test for Resistance to Polishing
Road Materials
5.
Degradation Test Some aggregates degrade in the presence of water. This is measured tlrrough mechanical agitation in water under designation test T-210 of AASHTO.
l. Z.
One good cnterion for pavement desrgn is the high coefficient of friction between the tire and the road surface.
A good asphalt or
concrete road design is when "the rubber tire is in direct with the aggregate and not with the binder" measured under the following considerations:
1. 2. 3. 4.
t26
If in so short
About 2.5 kilograms of coarse aggregate that is retained on No. 4 sieve are washed thoroughly and agitated for l0 minutes. Sedimentation test like the sand equivalent test for soil is done on the sample ing the 0.075 mm (no. 200) particles generated .The durability index result ranges from 0
to
3. 4.
a time, the aggregate surface of the road be-
comes polished and sticky, the coefficient of friction between the road surface and the tire will be dangerously low. The skid resistance has bearing relation with the polishing of the agregate, prompting the road agency to consider the skid resistance measurement on existing road to be included and part of the road inventory. Aggregates produced from limestone are practically susceptible to polishing. On the other hand, if the parent rocks are sandstone or fine grain igneous type, polishing is not severe. Limestone coarse aggregate containing larger amount of sand that are insoluble in diluted hydrochloric acid, are found to be resistance to polishing.
Likewise, the friction factor between the tire and the road surface will increase substantially if silica sand is included in the mixture.
100, but the FHWA specifications set
a
minimum
valve of35.
For fine aggregate that es the 4.75 mm (no.4) sieve, test is the same as the above procedures except that the sample size is only ll2 kilogram. The sand equivalent test is performed after 10 minutes to establish durability Index of 35.
Particle Size
l.
For dense graded pavement.
-
The particle size of ag-
gregate ranges from coarse to dust.
2.
For open graded pavement. - One or more layer of the ofuniform size is used.
coarse rock
3.
For sheet asphalt. - The mineral aggregate is a carefully graded sand and mineral dust.
For aggregates, the inherent variance in the materials, the in sampling and testing, the segregation in the sample and in handling aggregate of large volume will mean that erosion
Blements of Roads and llighways
Road Materials
"the sieve analysis may nol be rhe true representative of the material actually incorporated. "
2.
Wren crushed aggregate is specified, not less than -50 mass percent of the particles retained on the 4.75 mm No. a) sieve shall have at least one fractured face.
5-2 Aggregate for Bituminous Pavement
3.
Generally" for bituminous or asphalt pavement, the aggregates constitute 88% to 96Yo by weight or more than 75o/o by volume. AASFITO standard specifications provides that:
The fraction ing the 0.75 mm (No.200) sieve should not be greater than 213 of the fraction ing the 0.425 mm (No.40) sieve.
4.
The fraction ing 0.425 mm (No.a0) sieve shall have a liquid limit not greater than 35 and a plasticity index. range of 4 to 9 when tested by AASF{TO 'I-89 and T-90
"The aggregates shall consist of hard, durable particles of fragments of stone or gravel and sand or other fine mineral particles free from vegetable matter and lumps or balls of clay and ctf such nature that it can be compacted readily to form a frm, slable layer. It shall conlbrm to the grading requirements shown in tcrble 5-l when te,sted bv AASHTO T-l I and 27".
Standard
Altemate
u,s. std.
MASS PERCENT ING Grading Grading Grading
A
Grading
c 100
100
5s-100 40-100 20-50 6-20
70-100
1u
100
100
t0
318
s0-85
5
No.4
35-65
2
No. 10
25-50
60-100 50-85 40-70
0.5
No.40
I 5-30
2545
0.075
N0.200
5-20
5-20
Pavement
tion ofthese three.
B
25
5-3 Aggregate for Portland Cement Concrete In order to obtain high quality concrete, road a,qencies liave imposed almost without exception that all aggregates shall appropriate tests for strength, soundness, wear or the combina-
TABI,E 5-1 GRADING REQUIREMENTS SIEVE DESIGNATION
respectively
l.
non-hardening of the concrete. Under AASF{TO T-21 standard test, the aggregate is treated with a mixture cf sodium hydrochloride solution, and when the treated aggregate turns dark, organic materials are said to be present in the aggregate.
55-100
30-70 8-25
2.
The strength of fine aggregate is measured pression tests of sand-cement mortar.
J.
Soundness
aggregate is measured by the resistance
deterioration under the action of Sodium or N4agnesium Sulfate. The sodium sulfate test is five cycles. The maximum loss under AASHTO specification is l0%.
DPWH standard specifications. Coarse aggregate materials retained on 2.00 mm No.lO sieve shall have a mass percent of wear by the Los Angeles Abrasion Test (AASHT T-96) of not more than 45
offine
by the com-
to
The following materials are classified under item 300 of the
l.
The presence of organic impurities in the aggregates intended for concreting road pavement may cause slow or
4.
For Coarse aggregate the requirement consists of crushed stone, gravel, blast fumace, slag, or approved inert materials of similar characteristics or combination thercof
Elements of Roads and Highways
Road Materials
having hard, strong durable pieces free from adherent a
coatrngs.
bo C)
AASHTO Fine Aggregate grading By Weight Percent ing
a
sieve No. 4 sieve No. 16 sieve No. 50 sieve No. 100 sieve
z
trl
F
tsl
100
& (J
95- 100
o U I
318"
I
n
c'.
u)
oo
60
z
45-80
t0-30 2-10
tr trl F
a q;)
a.l
{
&
AASHTO M-80 (a
/ Materials
Pavements
Bridge Deck
u h
Chert (2.40 speciflc gravity ) Coal and Lignite
3.0% 0.5
rOO
or t--n AA .+
c.l
3.0
Materials ing No. 200 sieve
1.0
o trl
Sodium Sulfate Soundness
12
Magnesium Sulfate
18
I
a a
ooXn OT dcq
F rr)
ftl
o|.
o
oooo r)o o\
c\l
o o.l
e5
FI Fl Fl
o
t? ra trl
The Department of Public Works and highways Standard classi$ aggregate under item 703 and specificalll'provides that: Specificatio"ns
l.
Aggregate shall consist of hard, durable particles or fragments of crushed stone, crush slug or crushed or natural gravel. Material that breaks up when alternately wstted and dried shall be discarded.
6l
c)
oo
o
E9
o\
r.q 5b4 bQo
6
*z 6d
k
+R N= -'A
F-bhghe..,
Fl tn Fr
'.= t'l
s; :f
c.l oo
I(.)
co
o
z
Clay Lumps
a '5
oSRn. 9; dd:
FJ oo
a) bt)
.ir
r)
Roo :\ocoh
B &
,r,,4
c.l
LJ
tsl
I I
fL
dc\
c?)
TABLE 5.2 MAXIMI]M AMOI]NT OF'DELETERIOUS MATERIALS PERMITTED IN COARSE AGGREGATES FOR CONCRETE
tt rnc)orr|
AhOO
G)
a h
+t
ou 6qr
3
.,. o X-
?o.,; HEa Y€\
SSsV\l A:.;;A
zZzZziE
$-s !€es€T: et--fui\i. T,colT
= b6: 'aY,
a\ r:= o 7a
vc:
Ji'O
*
29,C lctO
i+it
Road Materials
Elenrents of Roads and Highrvays
2.
3.
Coarse Aggregate is the matcrial rctained on the 2 00 rnm (No.l0) sieve and shall have a percentage of rvater not more than 50 for sub-base and not more than 45 for base and surface courses as detennined bv AASHTO designation test T-96.
Fine Aggregate is the material ing the No.l0 sieve (2.00 mm) consisting of natural, cnrshed sand, and fine mineral particles. The .fraction Ttcsssit'tg the t).075 rnm (No.200) sieve should not be greater than 0.66 (.213) ot
l-he DPWH Standard Specifications relative to mineral filler states that:
"Mineral./iller shall consist off nely divided mineral matter cr"' rock dust, slag dust, hydrated lime, hydraulic cement, ash or other suitahle rnineral matter. It shall be free from fly organic impurities and at the time of use shall be sfficiently dry to flow .freel1, and shal.l be es,yentially free from agglomerations " such
AASHTO M -17 provides that:
the fraction ing the 0.425nun (No.40) sieve.
e,
Percentagc ing try'weight shall bc as follows:
For Base Course, the fraction ing the 0.425 mm No.a0) sieve shall have a liquid limit of not more than 25 and a plastic Index (Pl) not greater than 6. For sub-base course. the liquid limit should not be greater than 35, and
No. 30(0.66mm) sieve 50 No. 50(0 30rnm) sieve 95-100 No. 200(0"075mm) sieve 70-100
Plastrc lndex not greater than 12.
5.
For Surface Coarse the fraction ing the 0.425 mm (No. 40 ) sieve shall have a liquid limit not more than 35
AASI{TO fiirtlier stipulates that all minerals other than hydrated lime or Portland cernent, the Plastic lndex (PI) value shali be 4 or less.
and Plasticity Index not less than 4 nor exceed 9.
5-4 Mineral
filler
The strcngth of road pavement r.vill be increased if dust additives which dense the graded mixture is added. It is called mineral filler that redrrces the void contents in the mixture. This dust additive is not the ordinary dust that is being found in our
floor or tables.
5-5 Bituminous Material Bituminous material or Asphalt in short, is a viscous liquid used as binder for aggregates in road construction. At normal temperature, asphalt is either slightly thicker than water or hard but brittle material that breaks under a hammer blow when cold.
l.
Dust additive is classified into:
l. l. 3. 4 5. (t
Finel-v porvdered limestone Slag
Hydrated Linre Portland Cement
Trap rock dust Flv ash
2.
Bituminous material
is in liquid form when mixed or
cornbined with aggregates. This liquid form may be produced either by heating the hard asphalt, by dissolving in solvernt or by emulsi$'ing in water. However, there are bituminous liquid materials available and read-v for use. The action of asphalt binder depends on its tvpe and the aggregate it is combined rvith. The purpose of the asphalt binder is to resist the abr;rsive force brousht about bi,
heaw traffic.
r Road Materials
Elernents of Roads and Highways TABLE 5-4 SUGGESTED SPRAYING AND MIXING TEMP. ('C ) FOR BITUMINOUS MATERIALS AND ROAD TARS T+
3.
Surface Temp.
Type and Grade of Asphalt Asphalt Cement 15-140 120-145 120-155 130-165 130-170 105-135 135-165 135-165
80-120 80-120
AR-8000 AR-16000
13t165
80-'t20 80-120
20G30O pen.
1
AC-z.5
AC-5 AC-10 AC-20 AC-40 AR-100t)
AR-2000 AR-4000
12&150
8$100 60-70 4G50
1
150-175 15-150 120-155 120-165 1 30-1 70 130-175
Cutback Asphalt (RC,SC) 30 ( MC onV ) MC. 70
i
i
ss-1 , css-1
ss-1h, css-1h
RT10-'11-12
80-120 80-120 80-120 EO-120
80-120
80-120
80-120 80-120
80-120 80-'t2o
-
130+ 130+ 140+ 145+ 150+
30+ 50+
75+ 95+ 110 +
5G80 10-70 10-70 10-70 10-70
$ $ $
20-70 20-70
$
20-70
required.
5-6 Bituminous Binders Asphalt cement is used as binder for almost atl high types of bituminous pavement. Asphalt cerirent is a semi solid hyfuocarbon retained after fuel iurd lubricating oils are removed from petroleum. The softest grade r.lsed for pavement is the 200-300 penetration. The 60-70 penetrations is the hardest type.
Penetration refers to the consistencies of asphalt cement as described under AASHTO-T49. It is the distance that a standard needle penetrates a sample under known conditions of loading time and temperature. Recently, the procedure used in grading asphalt cement is the Viscosity Test rather than the Penetration Test. (see AASFIIO M-226 Specification for Transportation Materials).
6S.105 8S.120
Cutback or Liquid Asphalt
'l.
2S70
1+55
15.55
2765
27€5
65-105 80-120
6t105 8G120
Source: Asphalt tnstitute for Asphallic Materials AASHTO Guide Specs for Tars. + oF=g/soc +32 $ Temp. of the emulsified asphalt in the pugmill mixture. Rapid curing RC grades are not recommended for hot pugmill mking Max. Temp. asphalt cement and cutback asphalt shall be below thal at which fogging occurs.
ii "
road pavement is the open t1pe, consisting entirely of coarse particles and asphalt, heavy binder is needed requiring rnore asphalts. On the other hand, if aggregates in the pavemert contain fine particles, cohesion will be developed by surface tension in the thin asphalt film surrounding the fine particles. Hence, less viscous asphalt is
2S60
Road Tars RT1-2-3 RT$.6
RT7€-9
80-120
20+ 4.O+ 55+
250 800 3000 Emulsified Asphalt RS-l, CRS-1 RS-2, CRS-2 MS-1, MS-z, CMS-2 MS-2h, cMs-2h
130 + 140 + 140 + 145 + 150 + 135 + 140 + 145 + 145 +
If
2.
Liquid asphalt is a petroleum product consisting of asphalt cement with a liquid distillate (diesel, kerosene or gasoline). The less viscous asphalt contains diluents as little as l5%. The use of cutback is being frowned for two reasons: a. It is a usable fuel b. It is an air pollutant. Cutback or liquid asphalt is classified into: Slow curing (SC) road soil Medium curing (MC) cutback asphalt Rapid Curing (RC) cutback asphalt
Road Materials
Elements of Roads and Highways I
Emulsified Asphalt Emulsified asphalt is a kind of mixture wherein the mtnute globules of asphalt disperses in water. Asphalt contsnt ranges fram 55o/o-70% by weight. Emulsion could be applied or mixed at norrnal temperature, because when the water content evaporates, the asphalt remains. It has the following characteristics.
l.
Emulsifed asphalt is excellent with wet aggregate because the water medium carries the asphalt into a superior with the particle surfaces.
2.
is an altemate tc cutback asphalt for energ-v and environmental objectives. It is an effective material in coating electropositive aggregate such as linu:stone but tend to strip from aggregates with high content of silica for having strong elqctronegative sulface
Emutrsi-fied asphalt
charges.
3.
T\e Cctionic Emulsictn is very effective on high siliceous agg,regates but may strip from high alkaline that carry
The AASHTO classification of coal tars includes RT-l to RT-12 and RCTB-s to RTCB-6.
RT-l is
Rejuvenating Agent is an emulsified petroleum resin sprayed over the surface of an old asphalt road that changes to asphaltenes causing the binder to harden and cracks. The rejuvenating agent sprayed over the pavement and softening the binder. Too much application however, produces a slick pavement surface.
Oxidized Asphalt and Road Tar Oxidized asphalt is suitable only for roofing and similar applications. Highway used of oxidized asphalt is limited to water proofing of structures and filling ts of concrete pavement. Road tar is a by-product of the distillation process of coal. T'ars are produced from gashouse coal tar, cook oven tars and water gas tar. t.r6
of Prime
Cloat at
normal temperature.
The DPWH Specifications Classify Bituminous Tack Under Item 302 which provides that:
1. 2. 3.
Bituminous materials shall be either Rapid Curing Cut Back or Emulsified asphalt. Tack Coat shall be applied only to dry surfaces or slightly moist. No Tack Coat shall be applied when the weather is either foggy or rainy. Immediately prior to the application of Tack Coat, the road surf,ace is lightly sprayed with water, but not to be saturated.
4.
strong positive surface changes.
4"
suitable for application as Tack
5.
The rate of application of either the Rapid Curing, Cut Back or Emulsified asphalt is within the range of 0.2 to 0.7 liter per square meter. Any excess of this specified quantity should be blotted by sand or removed. Tack Coat shall be sprayed only as far in advance on the surface course as will permit it to dry in a tacky condition. Traffic shall be kept off the Tack Coat until after firlly dried.
Bitumen
-
Rubber Mixture
The bitumen rubber mixture for road pavement was experimented in Holland in the year 7929. It was adopted in the United States in 1947 and later, in European countries' The assessments of the road states that:
l.
Very little improvement gained as far as coefficient of friction on newly laid pavement but expect higher advantages after six months. The analysis of the Bureau of Public Roads states tlat:
t37
Road Materials
Elements of Roads and Highways
"An appraisal of the real economic value of the addition of rubber to asphalt must wait on further observation of the
for demulsibility b. Test for settlement a. Test
behqvior of experimental pavements uhder the influence of age, weather and
2.
Sieve test
trffic".
d. Cement mixing test
Particle charge and PH tests f. Miscibility and freezing test
According to the report, powdered rubber foams added to bitumen has improved the stability of some but not all.
5-7 Problems Associated with Bituminous
Epoxy Resin as Binders
Binders
Epoxy binders are produced in a clear, dark, rigid and flexible form for application to either concrete or asphalt pavement. Hardening can be auained by mixing the resin and the catalyst hardener prior to application. The result is called thermosetting. Meaning, it will not soften under the influence of heat or the action of solvent like water or petroleum products. The high cost of resin has restricted its use to bridge surfacing and other
l.
The thickness of asphatt film in the pavement, ranges from .005 to .010 mm. Test result showed that the thicker the asphalt film, the lesser is the process of aging. Where pavement has lower percentage of voids, aging is also
special non-skid seal coating surface only.
2. 3.
Test for Bituminous Binders
4.
l.
turely. One example is mixing asphalt with an overheated
Test of consistencv is subdivided into:
a. Kinematics Viscosity test AASFIIO T-202 b. Saybolt-Fural test AASFilO T-72 c. Engler specific gravity test AASFITO T 54 d. The float test e. Penetration test
f.
Softening point
test
AASFITO T-50 AASF{TO T-49 AASI-[[O T-53
2. Test for durability AASlffO T-52 3. Test for solubility AASFrrO T-44 4. Distillation test AASF{TO T-78 5. Thin film oventest AASHTO T-179 6. Flashpoint AASFilO T-48%79 7. Test for homogeneity of petroleum asphalt AASHTO 102 8. Special test for Emulsion asphalt AASHTO T-59 138
relatively low. Mixtures that are too dry, cracks and breaks easily. Higher asphalt content and lower percentage of voids may cause instability of the pavement. Improper construction procedures can age asphait prema-
5. 6. 7. 8.
aggregate.
Storing the mixed materials, or an extended period of mixing, the temperature produces substantial reduction of asphalt penetration.
Climatic conditions can seriously affect the behavior of asphalt binders.
Different brand or source has variability in behavior. The viscosity of some asphalt varies with temperature from that of the others. An asphalt meeting a specified penetration requirement at 77'F but with hrgh viscosity temperature ratio will become hard and brittle at lower temperature.
5-8 Bituminous Pavement The bituminous pavement
is a
combination of mineral ag-
t39
Elements of R.oads and Higtrw*ys gregate and binders. 'lhe mixture of rock material particles with asphalt has created so many natnes to wrt:
L Asphalt macadam Asphaltic concrete a Mastic 4. National paving 5. Plant mix 2
6. Asphalt sheet 7. Road mix 8. Armor coat
Road Materials
l. 2.
9. Oil mat etc.
Although several names were afrxed to bituminous pavement, yct, there is only ane thing to that, all bituminous roadways are nothing more than a mixture of mineral aggre,gates and asphalt. Meaning, asphalt road is virtually o Bituminous Rosd
3.
Viscous asphalt binder is heated to a fluid condition and mixed with heated aggregates. The mixture is then laid and compacted while still hot. Mixing liquid or emulsion asphalt with aggregates at normal temperature is either by plant or road mixing. The mixture is laid and compacted at normal temperature before the solvent evaporates or the emulsion breaks. Spread and compact the clean crushed stones, sprayed with heated or emulsified asphalt binder over it. Cover the sprayed pavement with fine aggregate. This process is referred to as the "penetrotion metltod."
5-9 Asphalt Concrete Pavement Qualities of Asphalt Road To consider an asphalt road in good service, it must posses in its full life the following qualities:
l. 2. 3. 4. 5.
The surface must be free from cracks or raveling due to shrinkage and fatigue failure. It mpst withstand weather condition, including the effect of surface water, heat, cold and oxidation. It must be resistant to internal moisture such as water vapor. It must posses a tight or porous impermeabie surface as the case may be suitable to underlying base on sub-base. It must be smooth riding and skid free surface.
The term Asphalt Concrete refers to a dense graded road surface made of hot mineral aggregates, mixed with hot asphalt and laid at high ternperature of about 275'F to 300'F. Asphalt concrete is the highest type of dense bituminous pavement suitable for the most heavily traveled roads. A prime coat is first applied over untreated and treated base before asphalt concrete is laid. The purpose is to bind any loose particles of the base and likewise act as bond between the base and the pavement to deter rising moisture from penetrating the pavement. The thickness of compacted asphalt concrete ranges from 2 inches for lightly traveled road to 6 inches or more for roads where traffic is considerably heavy.
5-10 Bituminous Pavement Failure The success of an asphalt pavement lies or depends on the construction qualrty of the sub-grade, and the base course. On the contrary, pavement failure would be considered as a foregone conclusion.
A satisfactory asphalt pavement could be attained under the following construction procedures :
Bituminous pavement failures are caused by excessive load. Heavy load creates deflection on the road surface, with insufficient underlying strength. Repetitious application of excessive load will roughen and crack the road pavement that ultimately result to complete failure of the roadway. Deflection on the road surface may be the effect of elastic deformation from the consolidation of the base and subsoil or from the combination of
140
t4l
Elements of Roads and Highways
Road Materials
elastic and plastic def,ormation. Repeated healy wheel load on highly resilient soil causes deflection leading to fatigue failure of the asphalt surface. Alligator or map cracking of the surface will be substantially evident. Elastic detbrmations in the subgrade penetrate to a depth of 6.00 meters although mostly to a depth from the surface.
Tire load
Tire load
--_-.,
I
Upheaval of surface and base
1. Surface Failure
FIGURE
2. Base
Failure
3. Basement Failure
5.1 PLASTIC DEFORMATION OF SURFACE BASE & SUBGRADE
Constructing the Macadam Asphalt Road
l.
Spread tlre coarsest aggregate to the roadway. Compact with either smooth wheeled roller or vibratory devices. 2. Smoothness of the surface is checked after compaction. Low spots are corrected by removing, replacing and recompacting the stones until smooth surface is attained. J. Apply asphalt by spreading the right amount of bitumen at specified temperature. The lower stone layer will not be coated if the asphalt binder is too thick. On the other hand, too fluid mixture will cause running of the binder down the underlying layers. 4. In placing the keystone base course, sufficient amount of smaller stone is mixed and spread on top to fill the interlocking voids, followed by compaction then spraying with
5. 6. 7.
5-11 Macadam Asphalt Mat Bituminous macadam road has large amount of voids in the lower part of the aggregate layers. The road strength originates from the interlocking aggregates that hold the individual stone together. Under this condition, a strong well drain base that will not squeeze upward into the pavement voids is required.
The Bituminous Macadam base or surface is composed of two or three layers of progressively smaller, clean, sharp angular stones bonded by asphalt. Each layer is compacted by rolling then sprayed with asphalt. Usually, the surface course is sealed by spraying a binder and blotted with fine crushed stones. The binder at the time of spraying is fluid enough to penetrate and coat the aggr egate particles. 142
asphalt binder.
Sealing of the surface is applied to seal the paveme,nt against moisture. These involve spreading of selected binder, spraying and rolling of the cover aggregates. During construction, the weather must be dry and warm. If not it is better to used emulsified asphalt as binder. Before the application of asphalt binder, coarse aggregate is first chocked with smaller stone to seal the remaining top voids, followed by spraying emulsified asphalt binder.
5-12 Surface Treatment Road surface treatnent method is applied to upgrade untreated surface and to rejuvenate an existing pavement. The inverted penetration method is applied wherein the binder asphalt is first prayed over a prepared surface then covered with fine aggregates. This procedure is in contrast with the penetration method wherein the spraying of asphalt binder is done after the placement of the aggregates.
On the basis of pu{pose to be accomplished, surface treatment is subdivided as follows:
143
Road Materials
Elements of Roads and llighwaYs
l. 2. 3. 4. 5. 6. 7. 8.
Dust palliatives to control dust.
Prime coat or tack coat treating the surface to provide new wearing coarse. Armor coats to provide protection for untreated surfaces. Seal coats and retreads. Sheet asphalts. Tack coats.
Slurry seals. Asphalt overlay.
The lighter medium curing cutback oil is generally used for prime coats. It is fluid enough to penetrate into the base course Lut retain viscous asphalt in the purses of the treated surface. Surface to be applied with prime coat binder, should be uniform without variations, properly shaped, moistened and rolled to have a plain uniform and solid surface-
Light tars grade RT-l to Rt-3 have been successfully used as prime coat. The amount of asphalt binder to be applied is from 0.3 to 0.8 gallons per square meter surface area dependrng
Dust Palliative
upon the tightness of the surf;ace to be primed.
Dust Palliative is a surface treatment or application of asphalt to control dust and fine sand along the highway.
After the application of prime coa! vehicular traffic should be detoured until after the surf;ace is no longer sticky. lf traffic detour is not possible, a blotter ofcoarse sand shouldbe applied
l.
2. 3. 4.
The road surface is treated with the application of about 0.2 gallon per square meter of lighLt slow curing oil. The material commonly used is the MC-70 but occasionally the MC-30 or the MC-70. This oil penetrutes the surface to about % nch and provides film that surrounds the particles and bind together. Slow curing oil is usually selected because it remains soft and last for quit longer period of time. Satisfactory result was also noticed when slow setting emulsions diluted in a mixture of 4 to 9 parts of water was used. Cut-back or Emulsion asphalt is unsatisfactory material for surface treatment as dust palliative. It becomes harder asphalts producing brittle surface that easily cracks in a short time followed by fast disintegration. Used crankcase motor oil is also considered as an effective dust palliative.
Purpose of the Prime Coat or Tack Coat.
l. 2. 144
To plug the capillary voids in the pavement in order to Stop the upward movement of moisture. ^fo improve adhesion between the base and surface course.
on top of the prime coat.
Armor Coat Armor coat is a surface treatment using a thin bituminous binder covered by mineral aggregate applied to an earth, gravel or water bound macadam surface or to stabilize the base' Surface treatment applied in two or more lifts is referred to as armor coats. When fund is limited, ,umor coat is used as temporary pavement and protection of the base materials.
l. 2. 3.
For two-course treatment' the maximum size of cover mao/o terials for the first lift is to I inch. For three treatments, the maximum size of aggregate cover is
l" tD l-Il4
inches.
The maximum size of aggregate for each subsequent lift should be reduced.
The surface treatnent, that follows the prime coat, could be $ as thin as % inch, or as thick as one inch. The thinner type 0'40 sometimes called, one shot type consisting of about 0'20 to 145
Elements of Roads and Highways
Road Materials
gallons per square meter of ailf, neavy liquid asphalt materials covered with 5 to l0 kilograms of clean,ir""n"d stone, or fine screened gravel, or slag which are free of dust. Larger cover
materials with maximum size up to yz,, or 5/g,, will require 15 to 20 kilograms per squ:ue meter surface area. Surface treafinent is applied on a clean, and dry surface, no wrnd and in good weather condition. For healy traific highway,
surface treatnent only serve as pailiative for sustain the traffic load.
it lack ,t
"igth
io
Seal Coat and Retread
seal coat is the application of asphalt binder to a pavement surface covered with aggregate. There is no specific distinction given between surface treatment and sear coit. However, seal coat is intended for temporary surface treatment with averase life duration of about I 0 years. seal coat is also intended to:
l. Provide an abrasion and water resistant surface. 2. To improve the skid resistance of bleeding bituminous surface which had been polished under traffic. To improve light reflection and no glare characteristics of pavement surface. To provide lane shoulder or other demarcations. To alert drivers that unusual dangerous condition is near
3. 4. 5. 6.
ahead.
Sometirnes the surface is sprayed with light coating of ss-lh Emrrlsified asphalt or petroreum .rri'to rejuveiate or improve its appearance. This treatment is sometimes called, Black Seal or Color Coat.
Sheet asphalt.
It
sheet asphalt is a mixture of sand fillers and asphalt cement. is about I Yz" thick cover asphalt concrete or shL of portland
cement concrete having a characteristics of noiseless. easilv cleaned surface extensively used as surface course on urban
streets. 146
The high binder content of 9%o ta lzyo by weight makes the sheet asphalt very expensive as comp:ued wrth other serviceable types. When binder is excessively applied to what is being required, the result is unstable slickly surf,ace which is dangerous when wet.
Cold Laid Asphalt Cold laid asphalt is a mixture of coarse and fine aggregates and liquid asphalt or emulsion. The mixrure can be prepared in a central plant or field mixture. A content of 5o/o to l0% liquid asphalt
is required to permit ioating. This type of mixture
is
acceptable for low volume roadway only.
Aeration before spreading maybe required for evaporation of some solvent water, otherwise, the pavement might be over lubricated and become unstable.
Slurry Seal Slurry seal is a combination of sand, crushed stone, emulsified asphalt and water. It is an effective solution in filling cracks and rejuvenating the surface of badly deteriorated surface. The mixture contains a proportion of 1,350 kilograms fine sand, 1,350 kg. rock dust and 140 gallons SS-l or SS-lh emulsified asphalt diluted with about 80 gallons of water on hear,y or light mixer. The purpose of the operation is to fill all cracks to produce coating of about 1/8 inch thick over the entire surface area of the road. If the seal is excessively asphalted, there is a danger that the road might be slicky under traffic.
Asphalt Overlay Asphalt overlay is a layer of asphalt bound aggregate laid to an existing pavement. The purpose is to level out distorted surface or to cover cracks and ts of the pavement. If the purpose is to strengthen the existing pavement, the choice is not overlay but Asphalt Concrete tightly bonded to the old pavement with Tack Coat.
l4l
Elements of R.oads and I{ighwnYs specified to bridge deck and other structures that require lighter load. Overlay thickness could be from 50 mm to 150 mm (2"to 6").
A thin asphalt overlay is normall-1'
5-13 Aggregate for Bituminous Concrete Coarse aggregate retained on a 2.36 (No 8) sieve should be either cmshed stone, crushed slag, crushed or normal gravel.
When cnrshed gravel is used, not less than 50 mass percent of the particles retained on a 4.75 mm (No.4) sieve shall have at least one fractured face. The coarse aggregate gradation when corrrbined with other required aggregate fractions in proper proportion, the resultant mixture shall meet the gradation required under the composition of mixture for the specific tlpes specified,
Only one kind of aggregate shall be used on the project except by direction of the Supervising Engineer
Fine Aggregates Fine aegregates ing the 2.36 mm (No.8) sieve shall consist of natural sand, stone screening or slag screenings or a
combination thereof. The resultant mixture of fine aggregates when combined with other required aggregate should meet the gradation requirements under the composition of mixture for the specific type as specified.
R.oad Materials
Lightweight Aggregate Lightweight aggregate, (except slag) could be manufactured by the rotary kiln process if permiued by the special provisiotts of the specifications. The materials shall consist of angular fragments uniform in density and reasonably free from flat, elongated or other deleterious substances. It shall also show an abrasion loss of less than 45 mass percent when tested in accordance with AASHTO T96. The mass per cubic meter shall not exceed 1080 kilograms after testing through 5 cycles of the magnesium sulfate soundness test. The loss shall not exceed 10 mass percent.
Aggregates for Bituminous Plant-Mix Surfacing 'The aggregate shbuld be uniformly graded from coarse to fine. Target values for the intermediate sieve should be established within the limits given on Table 5-5.
If the crushed gravel is used, not less than 50 mass percent of the material retained on the 4.75 mm (No 4) sieve shall be particles having at least one fractured face. That portion ofthe composite material ing a 4.75 mm (No.4) sieve shall have a sand equivalent of not less than 35 as determined by AASHTO T-l'16 altemate method no.2. The aggregate shall be free of cla-v balls and adherent films of clay of other matter that rvould prevent thorough coating with the bituminous materials.
Aggregates for Hot-Plant-Mix Bituminous Pavement Open Graded Asphalt Concrete Friction Coarse Relatively, pure carbonate aggregates or any aggregates known to be polishing should not be used as coarse aggregate. In addition, the coarse aggregate fraction shall have at least 75 mass percent of particles by weiglrt, with at least two fractured faces and 90 mass percent with one or more fractured faces except that lightweight aggregates need not meet this requirements. The abrasion loss shall not exceed 40 mass percent.
148
Various aggregates fraction for the mixture should be sized, graded, and combined in such proportions that the resulting conrposite blend meets one of the gradrng requirements as prescribed on Table 5-6.
Bed Course Materials Bed Course materials for sideu'alks, paved rvatenvat's and
Elements of Roads and Highways
Road Materials
curbing shall consist of cinders, sand, slag, gravel. crushec, stone or other approved materials having 37.5 mm (l'112")
Bed materials for slope protectron should be porous and effective draining materials consisting of sand, gravel, cinders, slag, crush stone or other approved free draining materials. It should be uniformly graded wherein 100 percent of the material will through a sieve having 37.5 mm square openings.
square openings.
TABLE 5.5 RANGE OF GRADATION TARGET VALUES Sieve
AASHTO
Designation
mm
inches
25
I inch
i9
3/a
475 2.i6
BITUMINOUS PAVEMENT
(Mass percent ing square mesh sieve AASHTO T-27)
Sieve Desisnati Std. mm
50-60 38-48
8
0.075 No
TABLE 5-7 GRADATION REQUTREMtrNTS -COLD PLANT MIX
filler
100 100
No.4 No.
Square Mesh and T-27 mineral Range
T-ll
3- | The minimum sand equivalent is 35
200
Altemate US Std.
100
25
1u
85-100
20
3/4'* 1I)n
40-70
100
l0-35
95-100
4-16
l5-40
0-5
t0-2s
No.4 No.8
s
2.36 0.600 0.300
A
(t v2.)
100
(1')
95-100
2s 20
B
c
100
54-15
68-86 56-78
4.75 (No.a)
3658
36-60
2.36 (No.8)
25-45
27-47
1.18
75-95 95-100
r
riI
0-5
(Mass percent ing square mesh sieves, AASHTO T-27)
G
100
95-100
100
74.92
95-100
2747
48-70 33-53
75-90 62-82
18-37
2240
38-58
l1-28
l3-28
1
5-30
2242
9-20
I
l-28
o-e
6-20 0-8
4-8
Grading designation corresponding size No. from
AAS
18-37
0.300 (No.50)
F
mm
l l-28
(No. l6)
0.075 (No.200)
E
100
t2 (ll2') l0 (3/8")
0.600 (No.30)
D
Sievc 95-100 68-86 56-78 38-60
(314',)
4-13
TABLE 5-8 GRADATION REQUIREMENTS FOR COVER COAT
Designation
3't
No. 30 No. 50
GRADING
Sieve In.
Course
t-1t2'
4.7
rnm
Wearing (surface)
Course
38
t2
TABLE 5-6 GRADATION RANGES-TTOT PLANT MIX BITUMINOUS PAYEMNNTS (lVlass percent ing square sieves, AASHTO 11 and T-27)
Bottom (binder)
4-9
':o
95-100 45-65 30-50 33-53
l-28
l0-20
2-10
3-8
1
100
t-_tt
z-s
38
In.
l-7/2"
l"
25 20
3/4"
t2
1/2u
l0
318'
4.75
No.4 No.8
2.36 4.75
No.200
No.5
No.6
No.7
TM No.8
No.9
No.l0
100
90-100
roo 90-100
0-10
100
9G100
0-l
5
85- 100
0-15
: U2
100
100
8s-100
85-100
n-')
0-10
0-10
o-z
o--2
o-2
r-il
Elements of Roads and Highways
Road Materials
TABLE 5.9 GRADATION REQUIREMENTS FOR BITUIUINOUS SURFACE TREATMENT AASHTO T-27 Grading desigration with corresponding size number from AASHTO M-43 (ASTM D-448) modified No.5 No.6 No.7 No.8 No.9 No.l0
Sieve
Designation
mm
38 25 20 12 l0
In
l-1/2"
SALT STABILIZED BASE COURSE Sieve Designation
mm
Grading A
90-100 100 2U25 90-100 100 0-10 20-55 9G100 lm
1"
3 4" t!2',
G5 -
318'
0-15 40-70 85- 100 100 lo0 0-5 0-15 10"30 85-100 85-l0O
PRESERVATTVE TREATMENT
Grading A
Designation
Sieve 20 mm
3t4',
l0-
3/8"
2.36 0.075
4s-80 28-64
45-80 28-64
0-12
0-12
FOR SUBGRADE MODIFICATION Sieve Dcsignation Mass Percent ing square mesh sieves -
mm t-r/2" 25 mm 1' 4.75 No.4 0.075 No. 200
AASTIIO T-27
25 20 12 4.75 2.00 0.300 0.075
':o roo 30-70 0-15
70-100
50-80
5G80
4U70
35-45 25-50
3G60 2G50
5-30
lG30
No.40
I
No.200
7-15
Sieve Designation
TABLE 5.T1 GRADING REQUIREMENT$AGGREGATES
"18
100
7-1s
(Mass perccnt ing squarc mesh sieves
38
-)
100
70-100
TABLE 5.13 GRADTNG REQUIREMENTS FOR AGGREGATES FOR EMTJLSIFIED ASPHALT TREAiED BASE
100
No. 200
0.425 0.075
-
Grading B 100
No.4 No.8
4.75
mm 3" 50 mm 2" 38 1-l/2" 25 ln 20 3/4" 10 3/g' 4.75 No.4 2.00 No. l0
Grading B
75
BLE 5-10 GRADATION REQUIREMENTS FOR BITUMINOUS
75 mm
Mass percent ing square mesh sieves
Inches
100
4.75 No.4 1.7(, No.8 0.150 No 100
TA
TABLE 5-12 GRADING REQUIREMENTS FOR AGGREGATE
40-8rJ
0-20
t-1t2' ln
Grading
AASHTO llT-27
Grading
100
100
95-100
95-100
314"
50-85
100
26-59
95-100 65-100
v2, No.4 No. 10 No.50 No.200
Grading
o-s
t7-48
0-2
2-rc
12-35
3-12
Road Materials
Elements of Roads and HighwaYs
5-14 DPWH Standard Specifications on Prime Coat, Tack Coat and Seal Coat. Item 301 Bituminous Prime Coat Materials Bituminous material is either Rapid Curing (RC) or medium Curing (MC) Cutback asphalt, whichever specified. Prime coat is applied only to dry or slightly moist surface. No prime coat will be applied during foggy or rainy days.
The pump is furnished with an indicator showing the rate of liquid flow. A thermometer is fixed to indicate the temperature of the liquid immediately before it leaves the spraying bar. 7. The distribution is fumished with a Tachometer indicating its forward speed visible from the drivers seat. 8. The distributor shall be designed where the deviation from the prescribed rate of application does not exceed l0% equipped with a device for hand spraying of the bituminous liquid.
6.
Application of Bituminous Materials Equipment
1.
2. 3.
4.
5.
l_54
The liquid bituminous material sprayed by a pressure distributor with no less than 1000 liters capacity mounted on pneumatlc tires of width and load produced on the road
surface not to exceed 1000 kilograrns per centimeter width of the tire. The tank must have heating devices able to heat complete charge of bituminous liquid up to 180"C. The heating device has automatic control that overheating will not occur. The flame should not touch the casing of the tank directly containing the bituminous liquid. The liquid should be insulated that when the tank is filled with bituminous liquid at 180'C, the temperature will not drop to less than 20'C per hour when the tank is not being heated. A thermometer is fixed to the tank to measure the liquid temperature continuously. The tank is furnished with calibrated dipstick to indicate its content. The pipes for filling the tank shall be furnished an easily changeable filter. The distribution has the capacity to vary the spray width of the bituminous liquid in maximum steps of 100 mm to a total width of 4 meters. The spraying bar must have nozzles from which the liquid is sprayed in fan-shaped over the road surface equally distributed over the total spraving width.
l. The
surface to be treated shall be cleaned with broom including the removal of all dirt and other objectionable materials before applymg Prime Coat. Prior to the application of Prime Coat, the surface is slightly sprayed with water but not saturated. 3. The rate of bituminous material application is within the range of I to 2 liters per square meter. 4. Prime coat should be left undisturbed for a period of 24 hours, closed to traffic until it has penetrated and cured sufficiently, so it will not be picked-up by the wheels of ing vehicles.
The Prime Coat should not be in excess of the specified amount. Any excess is blotted with sand or removed. 6. Area not accessible by the distributor is sprayed manually using the device for hand spraying. 7. The surface ofthe road and trees adjacent to the areas being treated shall be protected to prevent their being spattered or marred by asphalt. 5.
Item- 302 Bituminous Tack Coats
of
The standard specification for Tack Coat is the same as that the Prime Coat. The difference will be enumerated as fol-
lows: 155
Elements of Roads and HighwaYs Road Materials
l.
The manner of application is either by the Rapid Curing Cutback or the Emulsified Asphalt within the range of 0.2 to 0.7 liter per square meter.
Tack coat is sprayed in advance on the surface course to permit it to dry into a 'tacky" condition. The tack coat is maintained until the next course is applied.
2.
5. 5.
The aggregate shall have a mass percent of wear not exceeding 40 when rested by AASHTO T-96. When crushed slag is used, it should be uniformed in density and qualrty. A density of not less than 960 kilograms per square meter as determined by AASHTO T-96.
Item 303- Bituminous Seal Coat
TABLE 5-15 GRAITING REQUIREMENTS
This item consists of an application of bituminous materials with or without the application of aggtegate to a bituminous
Mass
Sieve Desigration
surface course.
mm
Inch
Materials Required:
12 l0
3/8"
l.
The approximate amount of materials required for Seal
4.75 2.36
l.l8
3
Grading
A
l/2
Grading B 100
No.4 No.8
Coat per square meter is provided on Table 5-14.
No.16 0.300 No.50
Bituminous material is the Asphalt Cement penetration grade 120-150 Rapid Curing or Medium curing Cutback
0.150 No.
2.
Type- 2
100
100
100
85-1000
85-100 50-100
85-100
l0-30
lG40
0-10
0-10 0-5
1'
0-10
asphalt.
3.
Cover aggregates for Type 2 Seal Coat consists ofsand or fine screening free from dirt or other organic matter.
4.
The aggregate for Type-3 Seal Coat is crushed stone, crushed slag or crushed gravel. Only one type of aggregate shall be used in a project unless other alternative tlpe is approved.
TABLE 5-14 QUAI\TITY OF'MATERHLS FOR SEAL COAT
Material
Type-l
Type- 2
Type-
Bituminous Material L/m
.20-.50
.50-1.00
.85-l/50
None
5.00-10.00
8.00-14.00
Cover
Aggregate Kg.lrf
3
Construction Requirements
1. Seal Coating should not be undertaken 2.
on foggy or rainy
day or when the surface to be treated is wet. Wet material Cover Coat, should not be used on the work
and no Seal Coating work be continued at niglrt unless
3.
4. 5.
provided with sufficient ligtting.
Seal Coating operation should not be started until the bituminous surface is thoroughly compacted by traffic and road roller. Seal Coating should not be placed on newly constructed or reconditioned road surface in less than ten days after the surface is laid and opened to traffic. Road surface to receive bituminous material should be cleaned of dirt, sand, dust and objectionable materials. The cleaning should be effected by means of a rotary power broom or power blower.
156
t57
Road Materials
Elements of Roads and Highways
Application Of Bituminous Materials
l.
Bituminous material should be applied by means of pressure distributor at the rate of approximately 0.9 to 1.8 liters for Asphalt Cement and 1.5 to 3.0 liters for Cutback Asphalt per square meter of surface in a uniform, unbroken spread over the section to be treated.
2. The pressure distributor
specifications including its appurtenances are the same as that enumerated in item 301 Bituminous Prime Coats. Those that differ will be disapproved.
3. 4.
5.
bituminous material at the junction of spreads should not exceed the specified quarrtity. Any excess should be removed from the surface by squeegee. [fnecessary to obtain properjunction ofspreads, a trip of Manila paper approximately one meter wide and at least as long as the spray bar should be used at the beginning and end of each spread. The paper is removed immediately after use. Any skipped areas or recognized deficiency should be corrected immediately by hand application of operated
Application
of
pressure device.
Spreading of Cover Aggregates
L
lmmediately after the application of asphalt, the cover aggregate should be spread evenly over the surface at the rate of approximately 0.004 to 0.007 cubic meters per
even distribution then rolled with an approved power roller weighing not less than 5 nor more than 6 tons to a uniform surface.
Item 304 - Bituminous Treatment This item consist of either single application of bituminous material followed by a single spreading of aggregate (single surface treatment) or two applications of bituminous material each followed by spreading of aggregate (double surface treatmenl) TABLE 5-16 QUANTITY OF MATERIALSAND SEQUENCE OF OPRATIONS USING CUT-BACK OR CEMENT ASPHALT Aggregate Grading and Sequence
Double
Operation
S.T.
FIRST COURSE: Applying Bituminous Materials, liter/ sq. m. Sprcad Aggrcgate: Grading B, kg. / sq. meter Grading A, kg. / sq. mcter SECONDCOT'RSE Applying Bituminous Matcrials, liter / sq. mctcr Spread Aggregato Grading B,kg. / sq. motor Bituminous Material, litcr / sq. meter Aggrcgatc, kg. / sq. mctcr
1.58 10.88 1.36 13.@
2.94 38.0
square meter. 2.
4.
158
Spreading of the Aggregate Cover is done through aggregate spreader, to obtain an even and accurate distribution. The used of spreader board attached to the tailgate of the tmck, should not be permiued. Tires of the aggregate truck should not be allowed to come in with the uncovered and newly applied asphalt. After spreading the cover aggregate, .the surface is broom lightly with an approved push or drag broom to insure an
Materials Requirements
l.
The approximate amount of materials per square meter and sequence of operation for single and double surface treatment is provided in table 5-16.
2.
The quantities given in the table are those aggregates having a bulk specific gravity of 2.65 as determined by AASHTO T-84 and T-85. 159
Road Materials
Elements of Roads and HighwaYs
3.
The supervising engineer may adjust the amount of asphalt material per square meter if necessary, to fit into the prevailing condition. But the total amount of aggregate per square meter after adjusting for specific gravity will not be changed.
Mass Percent Fassins Sieve Designation
Bituminous material for surface treatment is either slag or crushed gravel. Only one type of aggregate should be used in the project unless alternate type is approved. The aggregate shall have a mass percent of wear not exceeding 40 when tested under AASHTO T-96. When crushed gravel is used, not less than 50 mass percent of the particles retained on the 4.75 mm (No 4) sieve shall have at least one fractured face. When crushed slag is used, it must be of uniform qualrty and density of not less than 960 kg. Per
(AASF[[O T-19)
TABLE s-1? QUANTITY OF MATERIALSAND SEQUENCE OF OPERATIONS USING EMLTLSIFIED ASPIIALT
25 20 t2 l0 4.75 2.36 1.18 0.30
l.
Bituminous Matcrial, litcr / sq. mcter Aggrcgate kg.i sq. mcter
Grading
Grading
A
B
C
100
314"
90-100
t/2"
20-55 0-15
85-100
lm
0-5
10-30
85-100
0-10
lG40
0-5
0-10 0-5
318'
No.4 No.8 No. 16 No. 50
t00
The contractor or supplier shall furnish the engineer cerf-ified certificate in duplicate of the asphalt materials delivered to the site.
2.
S.T.
3. 1.58 13.@
SECONDCOURSE: Apply Bituminous Matcrial, liter / sq. m. Spread Aggregatc, Grading C, kg. / sq' m.
ln
Grading
Construction Requirements
Double Aggregate Grading and Sequence Operations FIRST COI.JRSE; Apply Bituminous Matcrial, liter / sq. meter Sprcad Aggrcgate: Grading B, kg' / sq. m€ter
Inch
mtrn
Bituminous Materials
square meter
TABLE 5-18 AGGREGATE GRADINC REQUIREMENTS
The contractor shall provide rveighing equipment on the site to control the application of aggregate. It ntust have an approved multiple beam twe scale with indicator and other necessary dials protected by a weatherproof house with floor area not less than l0 sq. meters. A mechanical spreader is used for spreading ther aggregate, capable of spreading the aggregate uniformll' over the full width of the area being treated, and shall irave a control to regulate the feed gates, the feed roll, the auger and truck hatch.
Application of Bituminous Material 1.58 13.60
1.
The application of bituminous material is done onll' rvhen
the weather condition is dry and favorable. Spraving should not be done unless the road temperature is above 20"C for at least one hour prior to the conrmencemcnt of
Elements of Roads and Highways spraying operation and the temperature is not less than
Road Materials trtem 305
20oC during the spraying.
-
Bituminous Penetration Macadam Pavement
Asphalt material is applied to the surface at least 24 hours after it has been Prime-coated.
The asphalt material should be applied on dry surface whenever cutback or asphalt cement is used. The surface
should be lightly wetted with water when emulsion asphalt is to be used.
lhe
This item consists of furnishing and placing one or more courses ofgraded aggregate and one or more application ofbituminous materials, followed by Seal Coat cover aggregate constructed on a prepared base. rABLE s-re
recommended application temperature for asphalt cement is within the range that produces a viscosity of l0 to 60 seconds savbolt fural. And for cutback Asphalt with
the range given in item Bituminous Material, the ideal tcmperature is rvhen fogging occurs.
Spreading the aggregates
Type ofAggregate and Sequence of Operations
of Bituminous Materials Asphalt Cement or Rapid Curing (RC) Asphalt
FIRST LAYER:
lmmedratell' after applying asphalt material, the dry ag-
gregate is uniformly and evenly distributed over the treated surface by an approved mechanical aggregate spreader.
2. Truck delivering aggregate
AND SEQUENCE
OF OPERATIONS
Spread
l.
QuANrrr"""sffirxffiLs
Aggregale 314"
Coarse Aggregate, kg.
/
sq. m.
on
Choker Aggregate, kg.i sq. m.
l0
Apply Bituminous Material, li1rlrl m2
5.5
SECONDLAYER:
shall move backward in
spreading aggregate to prevent the tires and the mechanical spreader from rolling directly over the newly sprayed asphalt.
3.
No portion of the sprayed surface shall remain uncovered for a period of more than 2 minutes. Immediately after spreading the aggregate, treated surface is rolled with an approved pneumatic tire roller.
4.
Asphalt materials that are exposed during rolling operation. should be covered r,vith additional aggregate and furtlier rolled until an even surface is attained.
5.
Traffrc should be prohibited from ing at speed in excess of 40 km. per hour before the asphalt material com-
Spread Aggregate Key Aggregate, kg./ sq. m. (112") Apply Bituminous material, literl mz
l0 3.5
THIRDLAYER: Spread Aggregatc Key Aggregate, kg./sq. m. Apply Bituminous material, literl m2
FOI.]RTHLAYER: Spread Aggregate CoverAggregate, kg./ sq. m.
TOTAL QUANTITIES: Bituminous material, liter / sq. m. Aggregate, kg. / sq. meter
pletelv set. 162 163
Road Materials Elements of Roads and Highways
3. Material Requirements The amount of materials per square meter and sequence operations shall be as provided in table 5 - I 9.
of
Bituminous Material is either Asphalt Cement Rapid Curing Cutback Asphalt or Emulsion Asphalt whichever is specified.
Aggregate should be crushed stone. crushed slag or cntshed gravel consisting of clean, tough, durable fragments, free from excess of flat, soft or clisintegrated pieces and free from stone coated u'ith dirt or other objectionable nutter. Natural gravel may be used for cover material. Aggregate shall have a mass percent of wear not exceeding 40 rvhen resred b-v AASHTO T-096. *When crushed gravel is subjected to five cycles of the Sodium Sulfate Soundness Test (AASHTO T-104), the weighted loss shall not exceed 12 mass percent. *When crushed slag is used, it shall be uniform density and qualrty. A density not less than 1,120 kilograms per sq. m. as determined by AASHTO T-19. Application of bituminous material should be made only when the aggregate is dry and the atmospheric temperature under the shade is l5"C or above and the weather is not foggy or rainy.
The roller should be self-propelled steel wheel, vibratory or pneumatic type. Its weight should be suffrcient enough to compact the layer of the required conditions.
TABLE 5-20 AGGREGATE GRADING REQUIREMENTS
mm
Grade
4.75
236
1.18
No.4 No.8 No.16
A
GradeB
!
GradeC
Grade D
100
9G100
35-70
Gl5 100
0-5
90-100 40-14 0-1 5
90-100 20-55
100
0-1 5
85- 100
0-l
)-u
5
10-30
0-10 o-5
Base Preparation
l.
Before spreading the aggregate, the base is properly cleaned of all loose foieign materials. The existing base is swept until the embedded large aggregate is erposed or in the case of previously constructed asphalt until the surface is free from mud or other covering.
The equivalent to be used shall include, a) I:land or power operated brooms, b) Shovel
c) Rakes. d) Self powered
bituminous material distributor hand or power operated spray pumps, broomdragging equipment and self powered rollers.
2. A
Inch
62 2-l/2" 50 2n 38 l-ltz' 25 ln 20 314* 12 712* l0 3/8'
Equipment
1.
Mass Percent
Sieve Designation
sufficient number
of
stiff-fiber steel bristle
push
2.
Prime Coat is applied to the prepared untreated base, or in case of previously constructed asphalt, or cement surface, Tack Coat is applied.
3.
During the application of asphalt materials, building paper is laid over the end of the previous application where the new application will start on the building paper.
4.
The distributor should not be cleaned or discharged into ditches, borrow pits or shoulder along the right of way.
brooms is included. 165 I
i
lii
164
Road Materials
Elements of Roads and Highways
Item - 306 Bituminous Surface Course Bituminous material is either Rapid Curing (RC) cutback, Medium Curing (MC) Cut Back or Emulsified Asphalt whichever specified. The proportion of bituminous material on the basis of total dry aggregate is from 4.5 to 7.0 mass percent when cut back asphalt is used and from 6.0 to 10.0 mass percent when emulsified asphalt is used. During the mixing operation, one half to one 0.5 to L0 mass percent of hydrated lime, dry aggregate basis is added to the mixture. The lower percentage limit is applicable to aggregate which predominantly calcareous.
l. 2.
3.
The equipment includes bituminous distributor and heating equiprnent, scarifier, mixer, spreader, and finishing compactlng cquipment. Road rollcr should be Self Propelled Steel Wheel tandem of 3 rvheel rollers weighing not less than 8 tons each and a Pnc:urnatic Tire Rollers having a total compacting width of not les than 1.52 mm (60 inches) and the gross mass
adjustable within the range of 3,540 to 6,360 kg./m. of compaction width. All tires of Pneumatic Roller is equally inflated exerting equal unit pressure with mass of varying pressure to suit project condition.
Base Preparation
Case I(NewAggregate) When new aggregate is used for the road mix surface course, the existing base is scarified lightly and bladed to a uniform grade and cross section as specified Case
1.
t66
- II
( Salvaged Aggregate)
When materials in the existing road surface are to be used for mixing, the surface is scarified lightly and bladed to a uniform grade and cross section. Tlie re-shaped surface is
scarified to depth as defermined by the Engineer to leave a foundation of undisturbed material parallel in profile
2.
and cross section to the finished surface.
The loosened materials are bladed aside into windrow side of the road, and {he undisturbed materials rolled, watered, and rolled as dirested.
5-15 Geoplastic Fabrics The Geoplastic fabrics were introduced and experimented in Europe in the year 1970. Thpy were used to reinforce soil of pavement and to provide drainage and erosion control for highways and railroads.
According to FF{WA report RD 80-021 enititled Evoluation Test Methods and Use Criteria for Geotechnical Fabrics in Highway application", the use of geoplastic fabric is considered as excellent. The evaluation was ed by Koemer and Welosh in "Construction and Geotechnical Engineering Use of Synthetic Fabric" published in New York year 1980.
The Functions of Geoplastic Fabrics
L 2. 3. 4. 5.
As Filter.It holds the soil in place while allowing water to flow easily away by some form drainage. As Drainage. Heavy geoplastic fabrics -provide channels for carrying water away from the soil to the drain. As Separator. The fabrics prevent different materials from mixing together. As Reinforcement.It adds mechanical strength to the soil of pavement structure. As Armor.It protects the soil from surface erosion or attractive forces.
Materials
Euplastic fabrics are manufactured from polypropylene, polyester, nylon, polyethylene and polyvinylidene chloride
of t6'1
Elements of Roads and Highways
CHAPTER
which changes in properties depends on the processes by which the fabric is produced aside from the differences in chemical composition. Most of these Geoplastic materials are made of polypropylene and polyester.
DRAINAGE AND SLOPE PROTECTION
Differences in Properties Includes:
1. Specific Gravity
5. Creep resistance
2. Strength 6. 3. Future stain 4. Modulus of elasticity.
Resistance to ultra-violet light and biological effect.
6-1 Drainage
Construction Methods are classified as either Woven or Knified non-woven. -l.or Woven Fabrics, the filaments are directed in two perpendicular directions and overlapped. For transportation use, the pattern is simple uniform and rectangular constant pore size distribution. The Monofilament Fabrics are woven from single strands and the Multifilament Fabrics are made h'om yarns with many fine strands. The Ribbon Filament Fabrics are made from strands with widths several times their thickness.
KGF) is made of loops of fibers by straight segments. They could be stretched in ei-
Knitted Geoplastic Fabrics corurected
ther direction without significant stresses to the fabrics. Knitted Geoplastic Fabrics in tubes serve well as filters around drain tile particularly for agricultural needs. Non-Woven Geoplastics are neither woven or knitted. The fibers or strand arrangements are held together under the following marmer:
l. 2. 3.
Needle punching through the fabrics.
4.
Combination bonding is the combination of two or more ofthe processes described to produce a particular charac-
Heat bonding or melt bonding
Resin bonding wherein the fabric is impregnated resin wh^ich cements the fibers together.
teristics.
I68
with
a
Drainage is defined as the me:lns of collecting, transporting and disposing of surface water originating in or near the right of way, or flowing in stream crossings or bordering the right of way.
ApproximatelS abofi 25Yo of roadway firnds are spent for culverts, bridges and other drainage stmchrres. Bigger appropriations are also allotted for ditches, dikes, charmels and erosion control structures of rural roads. Likewise, major capital investnents are channeled to urban areas for storm drains and other appurtenanoes plus the routine clearing of drainage facilities.
Surface drainage is only one :unong the many problems to be considered in establishing the location and construction of roads. The most favorable location of a roadway as far as drainage is concerneS, is the division bstween large drainage areas. All streams must flow away from the right of way to reduce the drainage problem. Roadway location parallel with the large streams should be avoided because it will cross every tnbutary canal leading to the streams. Steep grades, and heavy cuts and fill, should likewise be avoided for it will contribute to the problems of erosion. Surface drainage problems
l.
follow three basic considerations:
Hydreulic design that deals with estimating the highest rate of run-offto be handled.
Drainage and Slope Protection
Elements of Roads and Highw*ys
2. 3.
Hydraulic Design deals with the seiection of the kinds
drainage pattern. Water ing the natural right of ways several streams are collected, to under the highway through
is often intercepted by road cuts. The flow of
and sizes of the drainage facilities that is most economical to accommodate the estimated water flow. Erosion Control is to ascertain the design will not create erosion or other unacceptable en"ironmental conditions.
a single channel, diverting streams to canal or culverts that differ in sizes and length urcluding the flow characteristics from the previous one.
6-2 Hydrology Hydrology is that branch of physical geography that deals with water of the earth. The branch of hydrology that concern highway engineers are:
l.
2. 3. 4.
The frequency and intensity of precipitation. The frequencies that this precipitation brings the highest run-offwhich are equal or exceeded critical values.
The distribution of precipitation throughout the seasons that influences water behavior affecting the highway surThe prediction regarding future rainfalls or run-off from gathered statistical approaches, formula, or simulated msthods based on the laws of probability.
probability of error.
Runoff is Predicted Based on the Following Methods: Bythe Rational Methods. By the Empirical Formula. By the Unit Hydrograph. By Statistical Approach. By Simulation.
Relationship and Effect of Hydraulic and Construction
l. 170
Usually, highway construction disrupt existing natural
Construction operations may disturb the ground cover, and loosen the soil creating muddy stream as a result of erosion.
3.
Erosions create debris that are carried downstream, and deposited at points where the velocity slackens. Record shows that, almost every drainage installations disturbed the ecoiogical balance of nature.
4.
Any changes in the land use may alter the historical runoff or un-gauged rural water shed that could be disastrous on wide scale basis.
faces.
Concomitant thereof, any methods of predicting may be subject to substantial error. Therefore, design should make the best possible use of existing methods, with full expectations of high
l. 2. 3. 4. 5.
2.
Cardinal Rules on Drainage Design
l.
As much as possible, any exisfing drainage terns and soil cover should not be disturbed.
2.
system
Wt-
Necessary changes in the drainage patterns should not in any manner bring velocities that may create new erosion
problems. Non-observance of these simple rules have created many serious problems in the past, and worse, the people put their blame on those who were not involve in making the highways very unsightly.
6-3 Drainage Economic Considerations The term economy in drainage system, simply mean; finding the solution to a problem that is cheapest in the long run under the followins conditions: 171
Elements of Roads and Highways
l. 2. 3.
Determine the estimated initial investment cost. Consider the maintenance cost or outlay. Consider anticipated.loss and damage for each solution.
Under the foregoing considerations, arurual appropriation for possible drainage or economic loss is equal to the estimated losses from floods of various magnitudes, multiplied by the probability that these floods will occur any tirne of the year. For instance, if the drainage loss from any flood exceeding the design flow is P200,000 and according to hydraulic computations such floods will occur once in every 5 ysars, then the annual loss of flood damage is F200,000 divided by 5 years or
Drainage and Slope Protection road pavement under tlre influenc€ of the cross section slope or super elwation in the pavement and shoulders. If the water flow is controlled, then, the shoulder is in danger of erosion. However, t'he shoulder will have minimal erosion damage if it is already covered or protected by turfor grass.
1.
2.
Water flowng across tlre roadway down the road slope must be thin enough in a sheet form like so that the erosion on tlre shoulder will be minimized. Unprotected slope could be badly washed out if irregularity in the pavernerfi or shoulder accumulates water into small streams. Another point of water accumulation that endangers the shoulder is the low portion of sagged verti-
3.
cal curves. One way of preve,nting washout of the side slope is to retain the water at the outer edge of the shoulder.
P40,000 per year. Drarnage problem is varied" and there is no single sst of assumption or rule to economic problem in drainage, considering the uncertainty of flood frequency where the design is based. To major highways with large volume of traffic, losses to motorists
and to the economy, is tremendously high, closed frequently, due to flood and washout.
if
Turf slope not less than 0.12 Pavement slope approx. 0.04
the road will be
For major highways, projections might proved that drainage facilities should accommodate a 50 year flood, whereas, the desrgn based on a 5 year flood is reasonable for a low volume rural roads.
Low fill slope 4:1 or 6:1 approx. 1.5 m. High till slope 2:1
Where drainage problem of any magnitude has allernative solution, economic studies based on reasonable estimated costs and possible dam4ges, represent the best approach. Flood frequencies and some of the costs, must be thoroughly approximated and let catastrophic occurrences pervert our perspective
Shoulder Turf sloDe not less than 0.12 Paved slope approx. 0.04
on cost risks.
4:1 slooe or flatter
G4 Draining the Highway Rain water flows laterally or obliquely on the surface of the
FIGURE
A1
TYPICAL HIGHWAY CROSS SECTIONS
Drainage and SloPe Protection
Elements of Roads and Highways 4.
5.
A crown ditch or intercepting
channel mav be employed at the top of the cut slope. This will prevent erosion of the cut slope by surface runoff from the hillside above. The surface should not be disturbed in any manner where the natural ground is already covered with grass or other ground cover. The channel or canal should be formed making the origi-
nal ground as its bed and a small dike of topsoil or imported materials to serve as its bank. Scouring must be controlled. If possible, the water flow must be limited to a safer amount by diverting the flow at intervals. Water should be dropped down to the roadside ditch b]'means of specially designed conduit or channels.
c = Runoffcoefficient expressing rate of
I = lntensity of rainfatl in inches per hour for a duration equal to the time of concentration'
Ad = Drainage arca in hectares. On Freeways and urban strests, ttre inlets for gutters and median should the designed flood without clogging with debris. TABLE 6-1 SUGGESTED VALUE OF COETFICIENT OF RUNOFF C, FOR USE IN THE RATIONAL FORMULA
2. 3. 4.
On city streets, rain waters is guided by the road slope to the gutters and along wrth them the curb and inlets designed to limit the spread of water over the traffic lanes. AASFITO recommended that for a grade materials water should not encroach on the outer lane by more than 1.80 meters for a l0 years flood. A 50 years return penod is proposed for depressed facilities. The decision for water storm inlets and connections for gutters and depressed median should be based on the same periods. Main storm drain for freeways has to accommodate 50 to 100 years storm. For arterials, the return interval is 20 to 50 years. The water flow estimate was based on the Rational Formula using the value of runoff coefhcient between 0 8 and 0.9 for pavements; 0.4 and 0.6 for gravel, and 0.1 and 0.7 for grass.
RationalFormula: Q
=
clAd
Where:
Q: t74
Quantlty of runoff in cubic foot per second
Coefficiency of Runoff
Type of Drainage Area
Draining the Urban Street
l.
the ratio or
runoffto the rate of rainfall
Concrcte or Bituminous Pavcment Gravel Roadways, open Bare Earth ( high value for ste slope)
0.8 - 0.9
Turf meadows Cultivated fields
0.1 - 0.4
Forcsted areas
0.1 - 0.2
0.4 - 0.6 0.2 - 0.8 0.2 - 0.4
6-5 Manhole, Inlets and Catch Basin Manhole, inlets and catch basins are classified under Itent 502 of the DPWtl,,standard specifications which includes construction, reconstruction or adjustrnent of manholes inlsts and catch basin
Material Requirements:
l. 2.
Units' Whsn bituminous
coating is specifiled, it shall conform to ASTM D-1187, Asphalt Ease Emulsion as protective coating for metal' Sewer and manhole made of bricks from clay or shale must conform to AASIITO M-91 standard specifications' Building bricks of solid masonry units made from clay or shale must conformto AASIITO M-l14' Comrgated Metal
t75
Drainage and Slope Protection
Elements of Roads and Highways
3.
4.
t mortar mixture should be one part Portland cement and two parts fine aggregate (gravel) plus hydrated lime equal to 10% of the cemelrt by weight. Frames, gratings, covers and ladder rungs, should be assernbled before shipment and may be re-assembled readily'in the same position when installed. lnaccuracy of bearings must be corrected by machine. The frame, gating or cover to be used must constitute one pair.
Al1 casting should be uniformly coated wittr asphalt base emulsion meeting the requirements sf ASTM D-l18?.
Stuctural concrete for the purpose must attain a minimum 28 days compreSsive stength to 20.68 Mpa (3000 psi). precast unit must be cured and the water absorption of individual cores must not exceed 7 percent.
If
certified for use at 14 days from the date of casting. If the strength is not met at 28 days, atl units made from that batch will be rejected. Cracks in units, honeycombed or patched areas in excess of 2,000 squ:lre millimeters, excessive water absorption and failure to meet strength requirements will be rejected.
Construction Requirements Concrete conskuction must conform to the requiremeirts
for ltsm 4O5-Stuctureal Concrete. Metal frames should be set in full moitar bed and pipe sections flushed on the inside of the structure wall projected outside sufficiently !
i
2. 3.
for proper connection with the next pipe section. Masonry shall fit neatly and tightly around the pipe. When grade adjusftnent or existing structure is specified, the frames, covers and gratings are removed and then reset to the specified elevation.
Upon completion, each structure should be cleaned of anv accumulation of silts, debris, or foreign matters r:f, any kind until final acceptance of the work.
Methods of Measurement Standard manhole inlsts and catch basins be it new, or reconstructed will be measured in unit. Any authorized additional
concrete, reinforcing bars, masonry or labor required, will be measured and paid for under Item 404 and 405. Junction Box structure is measured for paynent as a manhole. The number of concrete covers, pairs of metal frames and gratings, pairs of metal frames and covers, will be rneasurecl as acceptably completed. Likewise, the number of existing manholes, inlets and catch basins will be nreasured as acctabll' completed.
Sufficient number of cylinders shall be cast from the concrete for each unit that will permit compression tests for 7. 14, and 28 days. And to allow at least 3 cylinders for each tests. tlrc strength requirement is met at 7 or 14 day, the units will be
l.
4.
6-6 Channel The purpose in deg a charxrel is to determine the cross section of the canal that will accommodate water flow smoothl,v and cheapest to construct and maintain.
1.
Side slope with a ratio of 2:l or even flatter is most acceptable, except on rock or other hard materials wfierr: channels are lined. For unlined or unfinished channel surface, the best cross section requires the least total excavations.
2.
The design of crown ditches, gutters, stream channels, and culverts flowing partially or fully, are based on the principles of flow in an open canal. For uniform flow, the relationship is expressed in the Manning Formula:
Q= vA = (ARz S1'z) nx3
where:
Q=
Quantitv of discharge in meter per second
Drainage and SloPe Protection
Elements of Roads and Highways
R_
Hydraulic radius in meter. This is the area of the
[=
flow across section divided by the wetted perimeter. Area of the flow cross section in square meter
s=
Slope ofthe channel.
|rf = Manning roughness coefficient
(see
table 6-2)
Unless the possibility of erosion is eliminated within a reasonable lirnit, channel design is considered not a completq unit.
1.
2. 3.
T,ABLE 6.2 REPRESENTATTVE VALIINS OF ROUGHNESS
Types of Lining Ordinary eartl5 smooth gravel
Rough rubble or jagged rock Rough concrete Bituminous lining Smooth rubble
Well maintarned grass-depth of flow over 15 on. Well maintained grass-depth of flow under 15 cm. Heavy grass
Value of n 0.02 0.04 0.02 0.02 0.02
0.04 0.06 0,10
The condition to various channel problems rest on the following distinctions:
a)
b)
Water flowrng down a mild slope in an open canal is in Sub-critical flow. Water flowing on steep slope is in Super critical flow.
Sub-critical flow exists when the depth of water in the channel is greater than the critical depth.
Super-critical flow exists when the depth is less than the critical level. The Critical depth occurs when the velocity head is one half the average depth.
The Average depth or Mean depth is the cross sectional area of the flow divided by its width at the liquid surface.
4. 5.
The actual velocity must be checked against the maximum values for unprotected earth. Where channel scouring is indicated, reduction of water velocity should be adopted to a safe level. To'reduce the velocity is to reduce the flow of water by diversion.
Where diversion is not possible, the channel is widened, or lengthened. As an alternative, the slope of the channel is decreased. Baffles, checks or drops are introduced to reduce slope in the channel.
TABLE 6.3 MAXIMT]M SAFE VELOCITY WHNN CIIANNEL EROSION IS TO BE PREVtrNTED
Tlpes of Lining
Allowable Velocity in ft. per second
Well establidhed grass on any good soil
6
Meadow type of blue or bermuda grass Bunch grasses, exposed between plants Grains, stiff stemmed grasses that do
2-4
Bend over under slnllow flow
Earth without vegetation Fine sand or silt, little or no claY Ordlnary firm loam Stiff clay, highly colloidal Coarse gravel Clay and gravel Soft shale
) 2-3
t-2 2-3 4 4 4 5
6-7 Culvert With the exception of storm drain, culvert
urcludes all closed conduits with standard designs repeatedly used'
Drainage and Slope Protection
Elements of Roads and Highways
l.
Culvert is loaded vertically by the wheel load of vehicles; the earth fill covering the culvert; and the horizontal ive or active earth pressure. The magnitude of these loads are uncertain as they are influenced by:
a. b. c. d. e.
2.
Depth of the cover.
Nature and density of the overlapprng and adjacent soils. Trench width and depth. Deformation of the pipe under load. Field construction procedures.
Comrgated metal pipes are more flexible that could tolerate greater deformations. The sides of the comrgated metal pipe deform laterally against the adjacent backfill under vertical load and the horizontal earth pressure increases the load carrying ability of the pipe. 4.
5.
Materials
The stress calculation for pipe culverts are based on the assumptions regarding the methods of under pipe soil at its sides and loading distribution over it.
Highway engineers rarely make struchrral design for pipes and culvert because of the difficulties and uncertainties involved. Instead, they used past experience and records as guide, then develop standard plans to fit all normal situations.
Corrrugated metal Plain or reinforced concrete Asbestos cement Vetrified clav or cast iron
FIGURE 6-2 CULVERT PIPE
mm]l Single
Double or multiple span
For concrete, vitrified clay and cast iron pipe, what is specified is the strength or class of pipe to be used in each condition. For comrgated metal pipe, highway engineers prescibe plate thickness for the different pipe size and the heights of fill.
nn
lt
is now the practice of relying much on the recommendations of various manufacturers who prepared all the de-
:
Single
) r
I
I I I
,J
Double or muftiple span
sign data and computations etc. 7.
180
Highway agency has standard drawing of various culvert desrgn appropriate for the more cornmon heights and widths of openings, heights of fill, including skew angles
FIGURE
G3
BOX CULVERT- REINFORCED CONCRETE
18t
Drainage and Slope Protection
Elements of Roads and Highways
Installation of Culverts In order to safeguard the culvert and to prevent subsequent settlement in the roadway surface, standard procedures for culvert installations are given special attention particularly the bedding (footing) and backfilling.
l.
.t
Culverts are installed
in the original bed of
10. The L qpe headwall create serious accident hazard, thus, gutter inlet with grate cover is recommended. I l. A wing type wall is recommended for large culverts. The flared U and warped walls are used on special applications.
Under Item 500 of the DPWH standard specifications, the construction or reconstruction ofpipe culverts and storm drains strearn with
are classified as Conduits.
their slope and flow line conforming to the natural channel or canal. The stream flow should not be disturbed to minimize the tendency of erosicn. ln mountainous or rolling terrain, departure from charurel aliggrment, either upstream or downstream, may divert the current flow to one side ofthe channel. This is dangerous to create erosion and deposition on the opposite side. Culverts on skewed channel are relatively longer and costly. But channel changes and erosion protections are provided with struclnres at one or both ends to reduce the
U . TYPE
skews. 4. 5.
Inverted siphons should be avoided rvhenever the water carrics sediments of debris. Stagnant water trapped inside the culverts sag is highly objectionable that must be avoided.
6.
n L
8.
I
l
Most culverts start upstream with headwalls and terminate doq'nstream with end wall. The headwalls direct the flow into the culvert proper, while the end walls provide transition from the culvert back to the regular channel.
WING TYPE
FLARED TYPE
Hydraulically, the headwalls and end walls functions separately but both retain the embankment and protect it from washout. In most cases, cut-off wall is extended to the level of expected scour. Sometimes a paved apron or energy dissipater is extended beyond the cut offwall. The use of small pipe as end wall and sometimes headwall is being discouraged because they are hydraulically inefficient as entrances. Instead, the pipe is extended beyond the toe of the embankrnent.
WARPED TYPE
STEPPED U . TYPE
FIGURE 6-4 TYPICAL HEADWALLS AND ENDWALLS FOR CULVERTS
Drainage and SloPe Protection
Slements of Roads and Highways
Conduits
-
2. The lower segment
of the conduit pipe should be in
with the shape throughout its full length.
Conduits are laid on bedding or footing that conform with the following standard specifications:
l. Z. 3. .1.
5. 6. 7. L 9.
Conduit Bedding is classified into Class A, B and C. In laying culvert pipes, the reqrdrernent of class C bedding is applied if no bedding class is specified.
Class
A
bedding shall consist
of a continuous
concrete
cradle conforming with the plan details. Class B bedding is extended to a depth not less than 30% of'the vertical butside diameter of the conduit pipe. The minimum thickness of the bedding materials bsneath the pipe is 10 centimsters composed of sand ing a 9.5 mm sreve but not more than l07o es 0.075 mm sieve. "trhe layer of bedding material is arranged and shaped to fit nr the conduit for at least 15% of its total height. When a bell and spigot type is used, the recesses in the bottom trench are shaped to accommodate the bell.
Ckiss C
bedding should be extendeel
to a depth not
Class A
Note:
Bc + 20 min.
1. For class B and C beddings, subgrades should be excavated or over excavated, if necessary, a uniform foundation free of protruding rocks may be provided 2. For class A or other unyielding foun' dation pipe should be free frrim shocks if blasting is anticipated in the area.
Class B Bc + 20 mrn pBc p max = 0.5
than llYa of its total height.
Pipe Cornrgation on Depth
Compacted
granular
1/6 Bc min
less
compacted
For flexrble pipes, ttre bed is roughly shaped and a bedding bl;r:rket of sand is specified as follows:
114 Bc
1/4 D min.
d
granular Granular foundation
material
Granular Foundation
Minirnum Bedding Depth
l0 mm
25mm
25 mm 50 mm
50 mm 75 mm
material or densely compacted backfill
Depth of bedding Material below pipe
Class D
D
smaller m. larger
.65 m and .75 to 1.50 1.65 m. and
dmin 75 mm 10O mm 150 mm
For a large diameter structural plate pipes, the shaped bed need not exceed the width of the bottorn plate.
Flat subgrade
Bc H
Laying tlre Conduit Pipe
D d
L lnstallation of conduit pipes should start at the down-
= outside diameter = bacKill cover above top of pipe = inside diameter = depth of bedding material below
stream end of the conduit line. 2.
The lower segmelrt of th€ conduit pipe should be in contrast with the shape throughout its full length. FIGURE
18,1
6.5 BEDDING CLASS AND LOAD FACTORS 185
Elements of Roads and Highways clAss A ReinforcedA3 = 1.0% Reinforced A3
Plain
=
0.4016
Drainage and Slope Protection 3.
Lt = 4.8 L1 = 3.4 Ll = 2.8
Bc + 20 min
4.
Bc + 20 min. Densely compacted backftll
y
lt9H
I
15 min
r.lo 10 min
Plain or reinforced
Compacted
concrete 2000 psi
granular
5.
The bell or groove ends of rigid conduits and outside circumferential laps of flexible conduits are placed with longitudinal laps or seams at the side. Paved or partially lined conduit pipes are laid with the longitudinal centerline of the paved segment coincides with the flow line of water. Elliptical and ellrytrcally reinforced conduits are placed with tlre major axis within 5 degrees of a vertical plan through the longitudinal axis of the conduit.
material Concrete Arch
ing the Conduit Pipes
Class C
backfill Compacted granular material Granular Foundation
1.
Compacled granular
a) Portland cement mortar or grout. b) Rubber gaskets. c) Oakum and mortar or t compound. d) Plastic sealing compound. e) A combination of these qpes or any other :rs rnay
Granular Foundation
15 min
D
Depth of Bedding Material below oiDe
65 m. and
dmin
smaller
75 mm
to 1.5O m 100 mm Lq5 m. and larger 15O mm
be specified.
.75
backfill
2.
Flat subgade
I
1. For class and C beddings subgrades should be excavated or over excavated, if necessary a uniform foundation free of pro-
truding rocks maybe provided 2. For class A or other unyielding foundation, pipe should be free
from shocks if blasting is anticipated in the area.
FIGURE
186
In ing conduit pipes, the ends are frrlly entered into the inner surface evenly flushed. ts are connected by:
material
€H Loose
Rigid conduit pipes are the bell and spigot type, tongue and groove, or other types that may be specified.
Lr = 1.5
Lightly compacted backfill
Oensely compactecl
Legend Bc = outside diameter H = backfill coyer obove top of pipe D = insidediameter d = depth of bedding material A3 = area of transverse steel in the cradle or arch expressed in 016 of area of concrete at invert or crown
J.
4. Source: American Corrcrete Pipe Ass.
6-6 BEDDING CLASS AND LOAD FACTOR
5.
t mortar for concrete pipes consists of I part by volume of Portland cement and 2 parts of approved sand with water necessary to obtain a refined consistency. Mortar should be used immediately within 30 minutes after its preparation. Mortar t is made with excess mortar to form a continuous bead around the outside t of the pipe and smoothly finished on the side. Rubber gaskets are installed to form a flexible waterhght seal. When Portland cement mixture is used, the completed ts are protected against rapid drying by any suitable covering materials. Flexible conduits are firmly ed by coupling bands. 187
Elements of Roads and l{ighwnys
Backfilling Backfilling follows after the laymg installation of conduit pipes under the following specifications:
l. Materials for backfill should be fine, readily compacted soil or granular material selected fiom approved sources. It should be placed on each side of the conduit for the firll trench width up to elevation of 30 cm. above the top of the pipe
Backfill rnaterials should be free from stones ttrat wculd be rstained on 50 mm sieve, nor chunks of highly plastic clay and other objectionable matenals. 3.
At least 95% of the grarrular backfill materials es the 12.5 rntn sieve and not less than 95% of it are retained on a4.75 mm sieve.
4.
Oversized materjals if present should be removed.
5
On top of the trench, backfill materials are placed at or near optimum moisture content and compacted in layers not exceeding 15 cm. (compacted) on both sides up to 30 centimeters above the top of the conduit. Care should be exercised to compact thorougNy the backfill under the haunches of the conduit.
7.
For that portion above the trench on each side of the conduit pipe, the width of backfill is equal to twice the diameter of the conduit or 3.50 msters whichever is smaller. After being bedded and backfilled, all conduits are protected by cover fill 1.00 meter high, before any heavy equipment is permitted to cross during the construction of
Drainage and Slope Protection
through shop elongation or by means of jacks applied after the entire line of conduit installed on the bedding but before backfilling. The vertical elongation should be maintained by means of sills and struts, or by horizontal ties used on paved invert pipe. Pipes and struts should be 30 centimeters in place until the embankment is completed and compacted.
Methods of Measurement Conduit pipe of different types and sizes whether new or reinstalled will be measured by linear meter installed. Conduit with sloped or skewed ends will be measured along the invert. Every section will be measured according to the number of units installed. Class B bedding (footing) materials placed and approved will be measured in place by cubic meter. When the Bid Schedule contains an estimated quantity for furnishing and placi4g backfill materials and pipe culverts, the quantity to be paid will be ttre number of cubic meter completed
in place and accepted, measured in final position between the limits as follows:
1.
Measursment include backfill materials up to the top of the original ground line but will not include any materials placed outside of vertical plane 45 cni. up outside and parallel with the inside wall of the pipe at its widest hori-
2.
The measurement will also include all backfill materials above the original ground line adjacent to the pipe for a height of 30 cm. above the top of the pipe and for a distance on each side of the pipe not greater than the widest horizontal dimension of the pipe if the original ground line is less than 30 centimsters. The measuremertt includes the placing of backfill materials in all trenches.
the roadway"
Field Strutting Whenever required by the plan and specifications, vertical diameter of rounded flexible conduits is increased by 5 percent
3.
zontal dimension.
Elements of Roads and Highways
6-8 Design of Underdrain Underdrain is categorized under Item 501 of DPWH Standard Specifications, which provides that:
"This item shall consist of constructing underdrain, using pipes and granular filter material underdrain pipe outlets and blind drains using granular material in accordance with the specifications and in reasonably close conformity with the lines and grades shown on the plans or as established by the engineer."
l. 2. 3. 4. 5.
The pipe is used to carry away collected water. The size and number of pipes and its locations of opening should be studied carefirlly to prevent excessive entrance velocrlv that will cause silting to the pipe. Filter materials with which the trench is backfilled or the opening in the filter, should be fine enough so that the adjacent soil will not be washed-out into the drain. The top of underdrain should be sealed with impervious soil to prevent the entrance of surface water. Intercepting drains must extend into the impervious zone. The pipes are laid with the flow line at least 1.20 meters below the finished grade and carefully bedded with gravel or filter materials.
Drainage and Slope Protection
5. 6.
acceptance.
Construction Requirements
l.
2. 3.
Materials should conform with the requirements specified as follows:
5.
2. 3. 4. 190
(AASfilO
Granular backfill filter materials shall be permeable meeting the requirements of AASHIO M-6 specifications except that soundness tests will not be required and minor variations in gradrng and content of deleterious substances may be approved by the engineer. All materials are subject to inspection before
4.
Zrnc coatd, (galvanized) comrgated iron or steel for culverts and underdrain (AASFIIO M-36). Extra strength and standard strength clay pipe and perforated clay pipe (AASHTO M-165) Porous concrste (AASI{TO M-176 Perforated concrste (AASIfIO M-175)
M-I77)
Asbestos cement perforated underdrain pipes M-189
Granular Backfill Filter Materials
Materials
L
Bituminous fiber non-pressure sewer drain and under drainage pipe system (AASSHTO
6.
Pipe installation. Trenches are excavated to ttre dimensions and grades required by the plan. A minimum of l5cm. bedding layer of granular backfill materials are placed and compacted at the bottom of the trench. Subdrainage pipe are embedded finnly on the bedding. Perforated pipes are placed with the perforations downward securely ed with appropriate fittings or bands. Non-perforated pipes are laid with the bell end upgrade with open ts wrapped with suitable material to permit entry of water, or unwrapped as may be specified. Upgrade end sections of all sub-drainage pipe installations are closed with suitable plWS to prevsnt entry of soil materials.
After the pipe installation, granular backfill materials are placed 30 centimsters above the top of the pipe and should not be displaced by the covering of open ts. The remainder of granular backfill are placed and compacted at every aft€r 15 cm. layers up to the required height. Any remaining portion of the trench above t}re granular backfill shall be filled with either granular or impervious material and thoroughly compacted.
l9l
Elements of Roads and Highways
Drainage and Slope Protection
Underdrain Outlet
6-10 The l,egal Aspect of Drainage
Trench for underdrain outlets are excavated to the depth and width as planned. Pipes are laid in the trench with all ends firmly ed and backfilled after inspection and approval of the
Flighway agency is legally responsible for any damage tcr private property affected by the changes it makes in natura! drainage pattem within the limit that water must flow.
pipe installation.
Blind Drain Trenches for blind drains are excavated to the width and depth as shown on plans. The trench is then filled with granular backfill material to the required depth. Any remaining upper
portions of the trench should be filled with either granular or impervious material in accordance with the requirements for
Damage claim against the Department could be established
1.
Wren as a result of the agency's project, the flow of several streams or creeks were concentrated into a single channel that resulted to erosion, silting or flooding ofpri-
2.
When due to poor design or inadequate rnaintenance rel="nofollow"> water backed against highway or embankment resulted to rnundation of land or property or caused irjury or death. Liabilrty however, is limited to damages lr direct conscquences of the improvement. The agency would not be li-
excavations.
6-9 Debris Control
3.
Flood waters usually carries objectionable objects like brushes, banana trunks, tree branches etc. These floating debris clogs culvert entrances and raise the headwater elevation overflowing the road and damaging ading properties. Culverts should be designed to allow debris to A single large span box culvert is preferred on streams carryrng large floating objects than the multispan culvert with the same area of openings.
Another alternative is to extend the curtain wall separating the barrels of the multi span culverts upstream, with its top slanting downward so that in time of flood, debris carried by flood water will ride up on this wall or turn to easily tluough the opening. Another method proven effective is to install up stream debris racks or wire, steel rail or piling. Some design provides trap for the sand or gravel carried by the stream rather than having it tlrough the stmcture. However, design of debris control devices depards upon the kind of debris to be handled, the volume of floodwater and the site conditions. 192
if:
4.
vate properb/.
able for damages if an unprecedented storm causes the stream to overflow a newly constructed channel, provided that this channel has the capacity equal to the natural volume of water flow. Engrneering decisions if based on an accepted practice, do not provide for a course ofaction. ln any case, the responsibility of the highway agency would be determineil through negotiations or court litigations. 'fherefore, design of drainage system must satis$ the various requirements of the environmental laws and regulations.
6-ll Roadway Design and Construction for Unusual Soil Conditions Problems usually encountered
in the design and construc-
tions of roadways are:
l. The stability of fill sand slope 4. Permafrost 2. T\e drainage 5. Elasticity and rutting 3. Capillarity and frost heave 193
Drainage and Slope Protection
Elements.of Roads and Highways
Stability of Fills and Slope
Original fill sloPe Slip surface
There are instances where the materials in cut bank slips down the roadway, or sometimes, a portion of high fill slides outward carryrng portion of the roadway. This pattem of failure is common in fills or cut slope of homogenous non-granular materials.
1. 2.
3.
4. 5.
Slides may happen during construction or at later date after the road is in service. It is advisable to risk some sliding or adjustments of large slope than to flatten increasing pay yardage. If possible during the location surveys, areas that are threatened by frequent slide, shc'uld be avoided. Minor slope adjustment, slides, and ledge falls that occur during construction should be removed to widen filI or to flatten the slope.
Slides may be caused either by mudflows, slope adjustment, or movement due to underground water or undercut rock strata. Slides happened when an underlying inclined surface of shale, soapstone, or the like is lubricated by seepage water.
Slides mayte controlled by removing large portion of the materials above the slippage surface, or by some drainage devices that keeps water offthe surface of weakness. Water must always be intercepted before it lubricates the critical slip surface.
Surf,ace of shear failure
Common Failure
FIGURE 6-8 COMMON FAILURE OF SLOPE
Capillarity Capillarity is the tendency of water to seek its own level as
if in an open channel flows through the pores a:rd fine channels of the soil. It is the force pulling free water through the voids of the soil in all directions.
Capillary action is most common in permeable rnaterials such as dirty gravel and soils composed mainly of fine sand" silts or clayey silts. Capillary flow however, is less common in impermeable materials like clay and colloidal soils.
L ln roadway
construction, moisture has to be controllerl. Over saturation of the soil in road structure reduces its
strength and the differential expansion of the soil due to uncontrolled moisture may lead to serious problerns. 2.
Original topography J.
F'IGURE
t94
6.7 MAN MADE SLOPE OF NEW SHAPES
Slumping of Fill
Moisture in the roadway is brought about by the changes in weather, seasons or by capillary action of the water. Water movement due to capillarity action take place in any directions, and an upward movement may create undesirable conditions. If the surface of the soil is open, evaporation of moisture is faster, and no damage may result, bug if the surface is covered with pavement or other impervious blanket, capillary water may accumulate and saturate the subsurface layers that usually resulted to pavement failure.
l9_s
Drainage and Slope Protection
Elements of R.oacis and tr{ighways 4.
5.
Consistency of soil .zaries fiorn semi solid to plastic irquid if moisture content is increased. The behavior of the material used is directly correlated with changes and percentages of moisture content. Voids in soils are of the same order of magnitude as the particle sizes. Thus, the height of capillary rise would be greater in fine grain soils than in coarse grain soils. Likewise, temperature piays an irnportant role in the capillary
Highly plastic soils should not be placed closer to
a L.
When heary loads itjs on a plastic soils, compression and rebormci occurs to at least 6 meters below the surface. B0% of tlre load is concentrated 90 cm. from the top of the surface. The design therefore, is to sum up the total expected load and rebound in the pavement to be sure that it does not produce fat.igue and failure in the pavement.
rise r:f water in soils. 'Ihe height of rise is gieater in low te.rnperature than in high tenaperaflire.
-
Deflection of the pavement surfbce as the wheel slowll' rolls past dre reference pornt is measured by a measuring device called Bankelman Bearn. A long slender bar slips into the space between the dual tires of the truck wheels. Deflection rate of travel shock wave is recorded.
TABLE 6-4 REPRXSENTATIVE IIXIGHTS OF
CAPILLARY RISE IN SOILS
Apgoximate Capillary Hei ehts Soii Tlpe Small grar,el Coarse sand Fine sand Silr Clay
Centimeters
Feet
2to l0
0.1to 0.4
15
0.5
30 to 100 100 to 1000 1000 to 3000
3to30
the
roadway surface where heavy loads are ex?ected. Early cracking of the pavement may happen due ro deformations caused by tlie rebound of the soil.
6-12 Stabilizing the Unsuppofred Slope
Ito3 30 to 90
An existing earth slope ihat have been stable can experience significant movement called slope failure or landslide due to the following physical changes :
TABLE 6.5 REPRESENTATIVE VALUES OF COMPRESSIVE STRESSES RESIILTING FROM CAPILI"ARY T'ORCES
a. Changes in natural conditions b. Changes induced by man Changes in natural conditions may be the result from:
200 to 2000 2000 to 6000
0.i to
1"0
1.0 to 3.0
l0 to
100
100 to 300
Elasticity and Rutting Elasticity is common in soils whose fines consist mainly of flat and flaky particles. This kind of soil has rubberized characteristic that rebound under heavy loads.
t96
l. Ocgurrence ofearthquake. 2. Subsidence ofunderground cavern. 3. Erosion. 4. Slope weakening due to the development 5. 6.
of cracks or urtrusions. by water shnnkage cracks that are followed Variations in the elevation of ground water or changes in
the slope subsurface flow that create new seepage forces. Weakening of buried soil or rock seams due to ground water flow or chemical leachine. 197
Blements of Roads and HighwaYs
Drainage and Slope Protection
Changes Induced by Man Grr
a.
b. c"
d.
Increased loading on a slope or near its crest. Removal of earth below the toe of a slope. Removal of materials from slope making it steeper. Topographic modification like earth moving, excavations, change in elevation from one areato another which may create slope failure. Landslide or other conditions caused by manSlope and Toe Failure typical for possessing internal friction
Slide Slide refers to the occurrence where the moving mass is defined and separated from the underlying and adjacent earth by
plane, comprising a number of adjacent planes were seepage result The seepage plane represent the continuous surface where the maximum shear strength of the earth material has been reached with the result that large displacement occurs.
Slide is classified into four:
l. 2. 3. 4.
Rotational slide. Translational slide. Block or wedge failure.
Base Failure typical for clay slopes underdrain by deep, hard stratum.
Flows and spread.
CofnAG-flto-
Ratioiral slide is associated with natural slopes and constructed embankment of homogeneous materials possessing cohesion.
Translational slide is associated with slope of layered materials where the mechanism of slippage occurs along a weak plane that possesses a downward dip and in cohesionless soil slopes where seepage occurs.
Block or Wedge'failure refers to the displacement of an intact rnass of soil due to the action ofan adiaccnt zone ofearth. l9l{
FIGURE
6.9 RATIONAL SLIDE 199
Elements of Roads and Highways
Drainage and Slope Protection
Firm clay Sofr clay with water bearing silt and sand layers Ftrm ctayey
FIGURE 6-10 TRANSLATIO\AL SLIDE
Flows and Spread failure is the nrost complex type of soil mass nlovement. Flow involves lateral rnoveJnent of soil having a clnractcrrstic uf viscous fluid, although the actual consistency of the moving mass may vary fiom very wet to dry. Spread refers to the occurrence of rnulti-directiorral lateral movement bv a fractured soil mass. Earthquake is a typical causes of lat*rai spreads.
Depositional area
-t^
FIGURE 6-12 FLOWS AND SPREAD FAILURE
6-13 Improving the Stabitity of Slope Slope areas that have experienced slides in the past should be considered likely to undergo further movement if loading
condition changes. FIGURE 6.1
2{Xl
1
BLOCK ANO WEDGE SLIDH
201
Drainage and SloPe Protection
Elements of Roads and Highways Procedures adopted in the past which have been successful in stabilizing slopes are enumerated as follows:
l. 2. 3.
Corrective and preventive measures of reducing a mass or loading have successfully prevented further slides. Improving the shear strength of the earth in the failure zone by constructing structural elements that will provide resistance to movement.
11.
Pile Driving, sheet piling or retaining walls are utilized to provide lateral and increase resistance of slope
tending to stocks. t2 Improvement and protective methods such as slope flattening and drainage control are preferred for economical reasons.
Consider the characteristics of the soil in the slope like:
a)
The thickness and depth of the materials involved in sliding. b) The ground water conditions. c) The spaces available to undertake corrective changes. d) The topographical conditions at the vicinity of the slope and the tendency for changes such as the advert of the seismic and vibratory loadings to occur. 4. 5.
Slope llattened or benched
Where area is available, flattening of the slop can be done to reduce the weight of the mass that tends to slide. If base failure is anticipated, placement of beam below the toe of the slope
6.
a.
will increase movement resistance.
lf the zone below the toe is susceptible to severe erosion, protective rock fill blanket and riprap catr be installed at the toe area.
7. To prevent infiltration,
b. Berm provided at toe
erosion and to reduce seepage force, the stone subsurface water and intercept surface water should be lowered.
8.
If the soil is cohesionless, the shear strength of the slope material can be improved ttrrough densification by using explosives or vibroflotation or terra probe procedures. For cohesive soils, shear strength could be improved by consolidation and water content reduction through surcharging which may include wick drains, electro osmosis and thermal drytng
10.
add cementing and bonding agent.
202
c.
Protection against erosion provided at toe
Where the weak condition is critical to the stability of the slope, grouting and injection methods could be utilized to FIGURE 6-
13 IMPROVING THE SLOPE STABILITY
203
I I I
i
Elernents of Roads and Highways
1. Drive pile closest to stope, then
2. Drive back piles last to reduce effects of driving on slope stability
d.
Provrde driven or cast in place piles
Lowered water
e.
table
Drainage and Slope Protection Settlement and distortion of a retaining wall due to compression of the foundation soil must be limited to a tolerable value. The combined effect of soil and water pressure on the retaining wall causes over turning moments and sliding forces greater than the condition where there is no water. To avoid the rise of water building up behind the retaining wall, a weep hole or collector drainage system or both ilre provided as part of the design construction. Weep holes should be at least 3 inches diameter provided with granular soil filter fabric at the wall to prevent backfill erosion. The horizontal spacing of weep holes ranges from 1.20 to 3.00 meters. For taller walls, two or more rows of weep holes may be provided with typical vertical spacing at l.50 msters.
Col,ector drahl perforated pipe in gravelfilter
Lowering ground water table to reduce pore pressure in the slope Removed soil
2:tltlm. plumb
Fill SloPe or
--f
.075 to .10 Weepl.bles
@ 1.50m. o.c.
: ' Ground FIGURE
6.14 IMPROVING THE SLOPE STABILITY
line
30x30x30 Gravel bacKill
6-14 Retaining Wall The practical use of gravity retalning wall is controlled by height limitations. Thus, the required wall cross section increases signlficantly with tall heights due to the effect of the triangular soil pressure distributed behind the retaining wall. If the ground water level rises into the backfill behind a retaining wall because of either changrng ground water condition or percolating water surface, the lateral pressure against the wall is also changed.
204
]x+o.om Dry Rubble
Cement Rubble
FIGURE 6-15 CROSS SECTION OF RUBBLE RETAINING WALL
205
Elements of Roads and Highways
Drainage and Slope Protection 1n"
0F-F-1 L- ls" -l
(a) Stralght Sectlons Used where tension valve of inter lock is cellular construction Piling ordered with required interlock strength specified and type of structure indicated Gravity wall
FIGURE
1n"
i-11R2"
b-F-r L-
i6"-J
Cantilever wall
6.16 REINFORCED CONCRETE RETAINING WALL
(b)
Z
Sec0ons
High ratio of beam strength to weight means maximum economy in steelsheet piling. Used primarily in filled bulkheads or other walls requiring high beam strength.
(c) Archweb Sectlons Designed for applications where Weep Hoeg 3 to 4'y' spac€d at 1.50 m. o.c.
Gravgl or Ftter Fabdc
a combination of beam strength and interlock tighness is required. Used generally in light bulkheads internally braced single wall
cofferdams, cut-ofi wall s.
FIGURE
206
7 DRAINAGE METJHODS TO PREVENT DEVELOPMENT OF WATER PRESSURE BEHIND THE RETAINING WALL
6-1
FIGURE 6-18 REPRESENTATIVE STEEL SHEETING SECTIONS
Drainage and Slope Protection
Elements of Roads and Highways
A good retaining wall
design must conform to the following
Excavation and Placing
requirements:
l.
The base and stem of the retaining wall must be capable of resisting the internal shear and bending moments developing as a result of soil and other loading.
2. 3. 4.
The wall must be safe against overturning. The wall structure must be safe against sliding.
The bearing capacrty of the foundation material ing the wall must not be exceeded.
Item 504 Rip Rap and Grouted Rip Rap This item includes furnishing and placing of riprap with or without grout; rvith or without filter backing. Stones for riprap shall consist of rocks as nearly rectangular in section as is practical except that riprap of Class A may consist of round natural stones. The stone shall be sound, tough, durable, dense, resistance to the action of air and water and suitable in all respects for the purpose intended. Class of Stone for Ripraping Class
A
- Stone ranging from 15 to 25 kg. with at least 50olo of the stones weighing more than 20 kilograms.
Class B
- Stone ranging from 30 to 70 kg. with at least 50%
The bed for riprap is excavated dorvn the requir*d depth properly compacted, trimmed and shaped. The riprap foundatio:r is dug below the depth of scour. The toe trench is filled with stone of the same class as specified. Stones placed below the water line are distributed properly and those above the water level are placed by hand or individually laid by machine with close broken ts firmly bedded into the slope against the ading stones
Each stone is laid with its longest axis perpendicular to the slope in close with adjacent stone. The riprap is thoroughly rammed into place and the finished stone are laid to an even tight surface. lntersections between stones are filled rvrth small broken fragments firrnly rammed into place"
Grouting When grouted riprap is specified, stones are placed by hand or individually laid by machine. Spaces between stones are then filled with cement mortar sufficient enough to completely fill all the voids exceptthe face surface ofthe stones left exposed.
Cement groufijs placed starting from the bottom to the top of the surface and then swept with stiff broom. After grouting, the surface is cured like structural concrete for a period of at least 3 days after the installation.
of the stones weighing more than 50 kilograms.
Class C
- Stones ranging from 60 to 10Q kg. with at least 50% of the stones weighing more than 80 kilograms.
Class D
-
Stones weighing from 100 kg. to 200 kg. with at least 50% of the stones weighing more than 150 kg
Where required, riprap shall be placed on a filtered layer to prevent fine embankment materials from being washout through the voids of the face stones. 208
Mrsonry stone is categorized under ltem 505 of the DPWH standard ipecifications. This item consists of stone masonrf in minor structures, in headwalls for culverts and raaining walls at the toes of the slope.
Material Requirements
1.
The stone should be clean, hard and durable. Adobe stone shall not be used unless specified. 209
Drainage and Slope Protection
Elements of Roads and Highways the backing by 30 centimeters minimum.
Item 506 Hand Laid Rock Emtrankment
Z.
When the wall thickness is 45 cm. or less, the header should extend entirely from the front to the back face.
Material Requirements
3.
Backings are built chiefly of large stones. The individual stones of backing and hearting are well bonded with the
Stones for hand laid rock embankment must be sound and durable furnished in a well balance range of sizes meeting the requirements as follows:
face wall and with each ottter.
4. All
openings and interstices in the backing are filled ccmpletely with cement mortar or with spall surrounded completely with mortar.
All stones should be more than 0.015 cubic meter in volume and not less than 75 percent of the total volume should consist of stones at 0.03 cubic meters in volume. Stones obtained from excavation performed under the
I
Pointing and Coping
contract may be used.
Adobe stone should not be used unless otherwise specified in the plan.
Cement mor[ar for ts on top of masonry surface are crowned slightly at the center to provide drainage. If coping is required, it should be indicated in the plan.
Where coping is not required, the top of the wall is finished witlr stone wide enough to cover the top of the wall from 45 cm. to 100 cm. in length and of random heighs of 15 cm. Stone is laid where the top course is an integral part of the wall. The tops of the top course stone are pitched to line in both vertical
Construction Requirements. Excavation shall be sufficient enough to expose the foundation bed. Stones are laid flat securely placed with their broken t lined. The larger stone should be generally located in the lower portion of the structlrre and voiCs eliminated to possible
2.
and horizontal plane.
Weeping Holes
All walls and abutrnents
extent.
Spall smaller than the minimum stone size are used to
3.
should be provided with weep holes placed at the lowest point where free outlets for water can be obtained and spaced not more thart2 meters center distance.
4.
Cleaning and Curing
5.
check the larger stones solidly in position to fill voids between the major stones laid in the embankment.
The exposed face of the rock mass should be uniform without projections of more than 15 cm. beyond the neat lines indicated on plans.
Backfill adjacent to the hand laid rock
embankment should be filled entirely with acceptable materials coming from the excavation iterns and compacted.
Immediately after laying and while the mortar is still fresh, should be thoroughly cleaned of mortar stains and should be kept clean until the work is complded. If weather is hot or dry, the masonry should be protected from the sun and kep wet for a period of at least 3 days after
Itern 5-7 Sheet Piles
the completion.
sheet
all face stones
212
This item consists of furnishing dividing and cutting off of piling covered by the specifications: 713
Drainage and Slope Protection
Elements of Roads and HighwaYs
Material Requirements
l.
Timber sheet pile may consist of any species that will satisfactorily stand driving It is sawn or hewn with square corners free from worn holes, loose knots, wind rhuk.., decay or unsound portions or other defects that might impair its strength or tightness.
Z.
Concrete Sheet Piles. Concrete reinforcement and marrufacture of concrete sheet piles should conform to the requirements of ltem 400 - Piling.
3.
SGaI STeelt-Pites sFould be of the type, weight and section modulus indicated on the plans or special provisions and conform to the requirements of item 400- piling.
Item 509 Gabion Gabion is a wire mish supplied in various width and length that is in multiple of 2,3,or 4 times its width. The height is equal to 1.2 or 1.3 the horizontal width equal to 100 centimeters with a tolerance limit of 3%o. The wire mesh is made of galvanized steel or plastic having a minimum size of 3.05 mm diameter. Its tensile strength should be in the range of 423.7- 686 Mpa
Construction Requirements
l. The wire mesh is twisted to form hexagonal opening of uniform sizes. The maximum linear dimension of the mesh opening shall not exceed 11 mm and the area of the mesh opening do not exceed 51.65 square msters. 2. The mesh should be non-raveling which means the ability to resist pulling apart at any ofthe trvists or connection when a single wire strand in a section is cut. 3. That the Gabions sides, ends, lid and diaphragms can be assembled at the construction site into rectangular baskets of the specified sizes. It should be of single unit constnrction. The base, lids" ends and sides should be either woven into a single unit or one edge of those connected to the base section of the gabion. 4. That Gabions could be divided equally by diaphragms of the same gauge as the body of the gabions into cells the length of which does not exceed the horizontal width. All perimeters of the edges of the mess forming the gabion should be securely seivedge so that by q'tng the selvedges the ts shouid have at least the same strength as the body ofthe mesh. 6.
60,000 - 85,000 psi.
For galvanized wire mesh, the minimum zinc coating should be 22.7 gru*r per 0.0929 mt 10.t0 o/sq. ft) of uncoated wire surface as determined by tests conducted in accordance with AASFNO T-65.
in
gabions are hard, durable rock pieces that will not deteriorate when submerged in water or exposed to seRocks used
vere weather conditions. Rock pieces should be uniformly graded generally in sizes ranging from 10 to 20 centimeters. FiU"O gaUiont thull have a minimum density of 1,400 kg/nt' and voids distributed evenly. The rock shall meet the requirements of AASHTO M-63 except that the sodium sulfate soundness loss should not exceed 99/o after 5 cycles. ')1,4
The tie and connection wire should be supplied in sufficient quantity to securely fasten all edges of the gabion and diaphragms and to provide for four cross corurecting wire in each cell whose height is l./3 or Yzthe width of the gabion and 8 connecting wires in each cell whose height equals the width of the gabion.
6-15 Highway Bridges HighwaV bridges are of two types:
1. 2.
Those that carry vehicular large stream.
traffic and pedestrians over
a
Those that separate traffic movements as interchanges and street pedestrians over or under crossings.
2lt
Drainage and Slope protection
Elements of Roads and ftrighways
tlydraulic Problerns
l.
There must be available strearn record that provides the usual method of estimating water discharges under the bridge.
2.
,A,nalysis of the channel relationship as to:
a. b. c. _t,
Peakflow Water way opening Water surface elevation at the structure and upstream and flow velocity.
Highway Bridges, Designed to Resist Loads Brought by:
l. 2.
The weight of the structure itself called'dead load.
3.
The weight and dynamic effect of moving load called "Live Load". The centrifugal forces developed by moving vehicles on
4.
curved structure. The wind load and the stresses brought about by:
e. Rib shortening
a.
f.
b.
Erection
flurrent+rsssus
h.
d.
The degree of confiaction of the flowing water in the
Earttquake
channel approach. +.
Final structure proportions and required channel modifications based on the studies.
5.
6.
Etfect of bridge opening and approaches that might cause flood to adjacent properties. This is associated with hydrauhc aspects ofbridge design. Econondc, legal and social implications where coopera-
tive planning with all affected groups and agencies is ry
8.
to
A bridge consists of substructure of abutments and piers that s superstrusture that carry the roadway between s. Bridge fype includes: slab, girder, truss, arch and cable stayed. Each suspension bridge has a distinctive form of structure, the selection of the kind of bridge to be installed depends on the length of individual span as follows:
necessary.
1.
Where the bridge is to rest on eroding streambed scouring is the primary concern. The problem of the designer is, if the design is over safe, it is over design, meaning, the foundation becomes very costly. But if scouring is under estimated, the foundation might be undermined which might result to total destruction of the entire bridge.
2.
Recent findings showed that the latest scours is when the pier has less resistance to flow. Meaning, that the piers are aligned with the flow rvith the smallest cross section that is best where scouring is a problem. Test results fruther showed that, scouring increases wilh depth of flow and becomes a problem in streams with high ratio bet$,een flood and normal flow
2
Bridge Types
3. 4.
Short span up to 18 meters which either: a.) Reinforced concrete rigid frame with slab deck. b.) T-Beam or box girders reinforced concrste. c.) Steel plate girders with reinforced concrete deck. Bridge of large span a.) Girder type rigid frames of reinforced concrete. b.) T-Beam or box girder reinforced concrste. c.) Steel plate girders with reinforced concrete deck Span that exceeds 90 meters long steel trusses, arches of steel or reinforced concrete. Span that exceed 150 meters are generally made of steel trusses, cable-stayed or suspension bridge.
For deg purposes, AASHTO has adopted vehicles as representative loadings
standard
:
2r7
Elements of Roads and Highways
CHAPTBR I Not less than 9.0O meterE
At least 18.30 m. greater than appmach pavement
Face of wall or pier
Face
of lltwAll
CONSTRUCTING THE ROADBED
Face of rail
7-l Roadway.60 m. min. ureater than approach way but not le6s than 7.30 m.
TUNNET ANO BRIDGES
UNDERES
Soil as Structure
Early road constructions have concentrated mainiy on the road surface pavement. Little attention was given to the subgrade, the base materials, and the manner of construction more particularly, tlre placing and compacting of the pavement foundation. As a result, too many road failures past and present were recorded with an endless maintenance and rehabilitation activities.
F IG
uRE&
1
e
R
Ec
oMM. -
"R
H
Xrrffiinr^AtD
o
R
rzo NTAL c LEARAN c E
For design pu{poses AASFfIO adopted standard vehicles that produce a representative loadings. HS 20-40 designation is a truck semi-trailer combination havrng a total weight of 36 tons. Trucks and other heavy equipment that contribute to the larger live loads has variety of total werght, axle loads and axle spacing. The number 40 indicates the year in which the loading standard was adopted. For minor highways, the standard vehicles are trucks weighing 20 tons(H-20) 15 tons (H-15) and l0 tons (FI-I0)
Because of these very expensive undertakings, hrghway agencies were prompted to undertake advance researches and studies on the properties of sub-grade and soil performance under severe conditions. After a long study of the unending road failures, road agencies have established a more detailed procedure regarding the kind of materials to be used on a particular condition, type and behavior of the soil where the road is to be constructed. Roadway has three major structural parts, namely:
l. Tlie Sub-grade or Sub-base 2. 3.
The Base Courso The Pavement
'The Sub-grade or Sub-Base is the earth beneath the road, properly arranged and graded, compacted and stabilized. It is defined as the "ing structure on which the pavement surface and its special under-courses rest. " In a cut section ofa road, the sub-grade is the original soil 218
219
Elernents of Roads and Highways
Constructing the Roadbed
lying below the layers designated as the base and sub base materials. On fill road sections, sub-grade consists of the imported materials taken from nearby roadway cuts or fiom borrow pit.
Construction and Maintenance Requirements of Untreated Gravel Road Surface
The Base Course is the materials laid on top of the subgrade consisting of crushed stone or gravel, sometimes mixed with asphalt binders. The Pavement is the material laid o'zer the base coarse consisting of Asphalt Concrete or Portland Cement Concrete.
FIGURE
7.1 ROADWAY STRUCTURE LONGITUDINAL SECTION
7-2 Types of Base Course Base course is classified into trruo t)?es:
l. 2.
The granular base course or untreated soil mixture. Treated base course.
l. That, the road must be stable to the super imposed loads without detrimental deformation. It must be resistant against various traffic activities and could withstand the abrasive action of traffrc. 2 It must shed the large portion of rain that falls on the surface because water penetrating the sub grade might soften it and loosen the surface stability. It must be free frorn large rocks or stones over one inch in diameter so that it could be regularly maintained by btading or dragging. 4. Gravel road must possess capillarity properties sufficient enough to replace the moisture lost through the surface evaporation. The road must maintain the desired damp condition that is required to bind the particles together. 5. On dry weather, the moisture film on the clay particles should bind the entire mass together, and in wet weather, the first rain that fall on the surface, should expand the clay and close the pores to prevent water from entering
6. 7. 8.
The granular base course is a road surface ofuntreated soil mixture described as gravel road. Gravel road consist largely of stone pebbles or crushed rock particles combined with either; clay, lime, iron oxide or other fine materials sufficient enough to serve as binder of the coarse particles. 220
L
If
and softening the materials.
An excessive amount of highly expansive clay materials should be avoided because clay will swell and unseat the coarser materials when wet and ultimately will weaken the stability ofthe road. Gravel road must be low cost. Funds for low traffic road is very limited that most of the time overlooked in the list ofappropriation priorities except on election period. Use local materials. Meaning, those materials that could be found nearby the project must be utilized.
the gravel surface road is to be maintained for several
years without bituminous or asphalt surface treatment or other
impervious surfacing, AASHTO standard specifications requires maximum liquid limit of 35 and a Plastic lndex of 4 to 9 and a maximumS%o ing the No. 200 sieve. 221
El3lents
3!
Roads and.Highways
Constructing the Roadbed
TABLE 7-1 GRADING REQTIIREMENTS FOR SOIL AGGREGATE MATERHLS (AASHTO Designation M-f47)
l. z.
to specified temperature and mixed with
Percentage by Weight ing Square Mesh Sieve Sieve Dcsig
mm Inch 150 2u 25 I' l0 318" 4.75 2.00
No.4 No. l0
0.425 No.40 0
075 No.200
Grading
Grading Grading Grading Grading Grading
DEF
BC
A
100 30-6s
75-95
100
100
4U75
50-85
6G100
25-55 300-60 15-40 204,5 80-20 lt30
2-8
5-20
100
100
35-65 50-85 55-lm 70-100 25-50 40-70 4G100 55-100 15-30 2545 2G50 30-70
5-15 5-20 5-20
8-25
Suitable for Surface Courses
Suitable for Basc and Sub-bases
To stabilize the base coarse. it is
either; Asphalt
Cemen! Cutback asphalt or Emulsion asphalt. The qualrty of asphalt is classified as either for stabilizing or for waterproofing purposes only. If the purpose is for stability, mixhrres are measured in the laboratory by the Marshall or FWEEM Stabilometer procedures. The weigirt of asphalt in percentage would
probablyintherange of 5Yoto1o 5. If the purpose is for waterproofing only, 2o/o to 3yo of the asphalt binder is added. 6. If Emulsion asphalt is used, enough water is included in the mixture to allow compaction at near optimum moisture content. .
Sand and Asphalt Base Course
7-3 Treated Base Course sometimes treated with
either Asphalt, Lime, Portland Cement or other materials as binders mixed with the aggregate base course. Treated base course is adopted if in the study or analysis of the highway agency, a better road can be produced at a minimal over all cos! or when a politician order the lughway office to construct the road with or without study because it was a commitment durtng the campaign period.
Asphalt or bituminous treatment is employed to waterproof and bind the granular aggregate to the sand and clay. Thus, the primary function of the asphalt in a treated aggregate, is waterproofing. Asphalt treated base allows a thinner over all depth of the pat'ement. Different types of asphalt are used to bind the natural materials like untreated granular base and granular aggregate with sands and even clay. The type ofasphalt binders for base course depends on several factors enumerated as follows: 222
J4.
100
The mixing procedure is either by plant or field mixing. If mixing is processed in the plant, the aggregate is heated
The sand and asphalt base course is composed of either, pit or river sand cemented wittr asphalt materials. In the early road construction, sand and clay rnixture is not only used as road surfaces but also for base courses. But lately, the Cutback asphalt, Emulsified asphalt or Tars have been introduced as substitute for the clay binders to produce loose beach sand, dune
quallty base courses for roads and highways. Sand for rmxing asphalt should be clean and strong, because the surface properties and grain shape must have the qualrty to resist displacement under load. If in the eveirt that quality of available sand is not satisfactory, it may be blended with sharp angular particles like crushed aggtegate, stone or screened slag, stone dust, loess, cement or other non-cohesive minerals to produce an stable mixture. The test could be by the Hubbard Field, Marshall and Hveem Stabilometer procedures.
Asphalt binders with the grade of asphalt cerneNil for hot plant mixing should be:
223
Constructing the
Elements of Roads and Highways
a.) Medium viscosity, rapid or medium curing asphalts. b.) Slow setting emulsified asphalt or c.) Tars of grade RT-6 to RT-10. The content of asphalt binder is in percent by weight ranging from 4oA tn l0%. Compaction is done using either pneumatic tired or smooth wheeled roller. In case the surface is tight and non-friable, sealing could be disregarded.
Fine Grain Asphalt Base An asphalt stabilized base and sub-grade constructed with fine grained has- a controlled Plastic lndex of 6 to l0 respectively. Aggregates with Plasticity lndex up to 30 are processed with lime. Those with up to 50o/o ing the No. 200 sieve and Plastic lndex up to 18 can be stabilized even without pretreatrnent.
Soil and Base Course Stabilized with Cement The use of Portland cement in stabilizing soils and aggreWar-l in 1914.
gates was initially practiced after World
1.
2.
3.
224
Cement stabilization by mixing natural materials and Portland cement compacted at optimum moisture content and cured to hydrate the cement is considerably strong and stable base. It is less susceptible to deformation caused by moisture and temperature changes. Comparatively, this is less rigid than the Portland cement concrete because its modulus of elasticity ranges from 100,000 for clay soils with little cement up to 1,000,000 for the strong mixture. Its compressive strength ranges from 300 psi to 600 psi with flexural strength of about 20o/o of the compressive value.
Portland cement concrgte modulus of elasticity ranges from 3 million to 6 million with compressive strength of about 3,000 to 5,000 psi.
R
oadbed
The stabilized cement mixture is called "Soil Cemenl" produced by using abundant native local materials subdivided rnto three types:
1.
Sandy and gravelly soils contarning less than 25o/o sllt and clay.
2.
Sand with lesser amount of fines like beach sand, glacial
3.
and windblown sand. Silty and Clayey Soils.
Materials having plasticity index greater than 30 is rarely used, unless lime is added. Materials with high PH or sulfate content are not advisable for use. The cement content fbr stabi" lized mixture ranges from 5o/o to l4Yo by volume of 3o/oto l6oh by weight of dry aggregates. Sandy and gravelly soils required less amount of cement, unlike the silt-v and clayey soils that needs higher percentage of cement. The dry densities of cement stabilize mixture compacted b1' AASI{|O standard methods, ranges from 135 lb per cubic fbot for a well graded gravel down to 85 lb. per cubic foot for silty or clayey soils, the recommended field density is about 95olo. The qualitS' of aggregate cement mixture is measured by its abilrty to resist abrasion and disintegration. Other methods of testing for stabilize cement content is the Unconfined and Triaxial Compression and Flexure Tests.
z-+ Grading and Maintenance of Untreated
Surface The cross slope of untreated surface gravel road must be sufficient enough to drain water to prevent potholes and softening of the roadway, thus;
1. If
the road materials are sufficiently stable and water tight, one inch per slope is considered satisfactory although 3/8 ta Yz" peer foot slope is prefi:rred. 225
Constructing the Roadbed
Elements of Roads and HighwaYs
2.
Ifthe road is steep grade, substantial cross slope is needed
5.
to direct the water into the roadside.
Compaction is effectively done by using pneumatic tired or steel wheeled rollers. Where surface is tight and nonvariable, sealing may be omitted.
Untreated surface road is seldom constructed in less than 20 ce.ntimeters loose depth. When compacted,'will be compressed Road development sometimes
to about 15 centimeters thick.
adopted the stage construction methods which means, step by step improvement of the roadway, depending upon the availability of funds and dernand of increased traffic. The sequence of improvement could be as follows:
First: It might be an earth road surface. Second: Untreated gravel road. Third: Application of asphalt over the gravel.
Fourth: The use of stone type pavement with gravel as part of the base cotuse. Maintenance of gravel road surface is a routine activity spe-
cially in maintaining the smoothness of the surface under the following procedures:
l. 2.
J.
By cutting off a thin layer of the road surface using road grader distributing the scraped layer uniformly over the roadway surface. The cut is deep enough to remove the comrgations ofthe road surface. The blading sequence is once or twice a year or sometimes monthly, depending upon the finances, traffic and equipment availability. After blading, the road is compacted by road roller to maintain the cross section slope and th: crown of the roadway. The most effective routine maintenance is done immediately after rainfall where the surface is soft for the blade to drag. Losses of materials caused by grading and traffic wear generally ranges from Yr" to 1 inch of the thickness per year allhough it varies due to traffic volume, rainfall, wind intensity, frequency and maintenance practice or habit.
226
7-5 DPWH Standard Specifications on Aggregate Sub-Base Course The Department of Public Works and Highways classified the aggregate sub-base course as Item 200 which consists of furnishing, placing and compacting aggregate sub-base course on a prepared sub-grade.
Item - 200 Material Requirements That, aggregates for sub-base shall consist ofhard, durable particles of fragments or crushed stone, crushed slag or crushed or natural gravel and filler or natural crushed sand or other firrnly divided mineral matter. The composite material should be free of vegetable matter' and lumps or balls of clay that could be compacted readily to form a firm stable base. TABLE 7-2 GRADING REQTTREMENTS FOR ITEM 200
Conditions
l.
The fraction ing the 0.75 mm (200) sieve should not be greater than 0.666 (213) of the fraction ing the 0.425 mm No. 40 sieve. 227
Elements of Roads and Highwa5,s
2.
Constructing the Roadbed
The fraction ing the 0.425 mm (No. 40) sieve should have a liquid limit not greater than 35 and Plastic Index not more than 12 as determined by AASHTO T-89 and T90 respectively.
3.
Req
u
irements
l. 2. 3.
TABLE 7-3 GRADTNG REQUIREMENTS FOR rTEM-201 Sieve
Mass Percent
Standard Altemate US Standard 50
2u
38
1-l12
z>
1u
20
3/4" 7/2'
12
4;t5 0.425 0.075
No.4 No.40 No.200
The materials ing the 20 mm (3/4") sieve shall have a soaked CBR value of not less than 80%.
Item- 202 Material Requirements
The coarse portion retained on a 3.0 mm (N0. l0) sieve shall have a mass percent of wear not to exceed 50 by the Los Angeles Abrasion Tests as determined by AASHTO T-193. The CBR value should be obtained at a mum dry densit) as determined by AASHTO T-180 Method D
Tfeml[Ot lfaterial
4.
Grading B
4.
The portion ing the 0.075 mm (No. 200) sieve shall not be greater than 0.66 (Zl3) of the portion ing the 0.425 mm (No. 40) sieve. The portion ing the A.425 mm (No. 40) sieve shall have a liquid limit n(lt more than 25 and Plastic lndex not more than 6.
The coarse aggregate retained on 2.0 mm (No.lO) sieve shall have a mass percent of wear not more than 45 by L.A. abrasion tests, and not less than 50 rnass percent shall have at least one fractured face.
The material ing the 20 mm (3/4") sieve shall have a minimrrm soaked CBR value of 80%.
TABLE 7- 4 ITUNI 2(T CRUSTfID AGGREGATE BASE COURSES 60-85 oo-as 35-65
20-50
30-35
Mass Percent
Standard Altemate US Standard mm lnch
8-25
38
o-12
2-t4
25
I'
20
3/4*
t2
712',
4.'t5 0.425
No.4 No.40 No.200
0.075
That the fraction ing the 0.075 mm (No. 200) sieve shall have a mass percent of wear not to exceed 50. The fraction ir4l the 0.425 mm (No. 40) sieve shall have a liquid limit not greater than 25 and Plastic Index not greater than 6. The coarse portion retained on a 2.0 mm (No. 40) sieve shall have a mass percent of wear not to exceed 50. 228
B
t-t/2'
s-20
Conditions
Grading
100
60-85 60-90 30-35 8-25
35-65
2-14
5-1 5
l0-30
Item* 203 Lime Stabilized Road Mix Base Course This item consists of foundation for a surface course comof soil aggregate, lime and water proportion mixed on site and constructed on a prepared sub-grade or sub-base. posed
'229
Constructing the Roadbed
Elements of Roads and Highways
4.
Material Requirements
1.
Soil aggregates refers to the combination of gravel, sand, silt and clay, or other approved cornbination of materials free of vegetable or other objectionable matter that might be encountered in the construction site or obtained from other approved sources.
2. 3
The intent of the specification is to utilize soil existing on the roadbed if the quality is satisfactory according to the specifications and minimizing cost. On the contrary, if the material quality is poor or deficient, aggregate must be obtained wholly or partially from
"
5.
The equipment to be used includes: scariSer, pulverizer, mixer, spreader, hauler, water truck, compactor and finishing machine, including slurry line distributor equipment.
Distributor equipment should include: pressure gauge, volume measuring devices or a calibrated tank. It should "be equipped with power unit for ttre pump and full circulation spray bars adjustable laterally and vertically and also agitator to prevent settrng of solid lime.
Preparation of the Soil Aggregate
an approved outside sources.
Case
TABLE 7-5 GRADING REOTIREMENTS FOR ITEM.2O3
l.
Standard Alternate US Standard mnl
Inch
Mass Percent Pas Gradrng
100
2"
4.75
No.4
55-100
2.ffi
No. l0
45-100
0.425
No.40 No.200
25-80
0.075
I l-35
The existing roadbed is scarified lightly and bladed to a uniform grade according to the plan, then rolled, watered and rolled.
2. All depressions appearing on the surface are filled, and
B
50
- I For New Soil Aggregate
the weak portion of the roadbed is strengthened with new
3.
soil aggregate.
Allow one day for measuring, sampling and testing of the sample for approval of the qualrty and gradation before spreading the windrow for application of the hydrated lime.
4. If soil aggregate moisture
exceeds two mass percent of aeration by harrowing the soil aggregate until the moisture content is reduced to 2o/o or
th" dry aggregate, apply Conditions:
l. 2. 3.
5. That, the Plastic Index of Item 203 should not be less than 4 or more thar 10. The aggregate mass percent of wear should not exceed 50. Hydrated lime must conform to the requirements of Item 701- Construction Lime. The amount of lime added to soil aggregate should be from 2to 12 mass percent of the dry soil. Lime should not be applied during windy, rainy or with
less.
Finally, spread the aggregate smoothly and uniformly over half the road or other convenient width of the surface ready for the application of hydrated lime.
Case
l.
- 2 Salvage
Soil Aggregate
When materials in the site are to be used for mixing, the surface should be scarified lightly and bladed to a uniform grade conforming to the cross section of the plan.
impending bad weather. .:1J I
230
Blements of Roads and Highways
2. 3.
Constructing the Roadbed
The reshaped surface is scarified again to depth required leaving a foundation of undisturbed material parallel rvith the profile and cross section. The loosened materials are bladed into a windrow at the srde of the roadway. The undisturbed materia-ls are then rolled, watered and rolled.
then mixed by blading the mixture from side to side of the road, or by manipulation producing equivalent results until the whole rnass has uniform color. The mixture should be free from lean spots or balls of unmixed parti-
2.
Application of Lime
3. Application of lime shall follow correct procedures enumeratod as follows:
l. 2. 3. 4 5. 6. 7.
The hydrated lime is uniformly spreaded at specified percent using either the dry or slurry (wet) methods. The hme is distributed in successive applications at the arnount and intervals as prescribed. The rnixing equiprnent follows immediateiy behind the distributor after each application to partially mix the lime n'lth the soil aggregate. lt is applied only to specific areas as can be mixed into the soil aggregate during the day of application. Dry upplication is either by spotting bags of lime in equal pre-determined transverse and longitudinal intervals or by applying in bulk lime from equipped self-loading trucks. If lfune slurry (wet) is employed, the typical slurry ratio is 1,000 kilograms lime to 2 cubic meters water. The achtal mixing proportion depends upon the percent of lime specified, the tlpe of soil and its moisture condition. To prevent run-off and consequent non-uniformity of lime distribution, the slurry is mixed imrnediately after each spreading .
Mixing
4.
:3?
After the last lime application and partial mixing, the entire rnass of rnixture is withdrawn on the road surface and
Should the mixture show an excess of deficiency or uneven distribution of lime, the condition must be corrected by adding soil aggregate or lime then remixed. tf the mixture contains excessive amount of water or volatile matter, as may be encountered in slurry operation, it should be bladed, aerated or manipulated until the moisture and volatile content becomes satisfactory. Whether mi*ing is completed or not, all loosened materials are bladed into a windrow at the end of each day work and retained as such until operations resumed.
Spreading Compacting and Finishing The methods of spreading, compacting and finishing are enumerated as follows.
l.
The materials are spreaded by self-propelled pneumatic tired blade grader or mechanical spreader of approved type. Cutting into the underlying course should be avoided.
2.
After spreading, the surface is leveled to the road centerline, then to the outer edges of the road overlapping the shoulder.
3.
Each should terminate at least 90 centimeters in advance or to the rear ofthe end ofthe preceding .
4.
During the time of compaction, the surface is dragged or bladed as necessary to fill and remove incipient corrugation or other surface irregularities.
5.
Rolling must continue until after the surface is in uniform texture satisfactorily compacted.
lvlixing procedures are enumerated as follows:
L
cles.
233
Elements of Roads and Highways
6.
Constructing the Roadbed
Rolling should be stopped whenever there is an excessive pulverizing of the aggregate or displacement of the mixture.
Protection, Curing and Maintenance
After stabilizing the base course by lime,
it is protected
against rapid drying for a period of at least 5 days by either of the following curing methods:
l. A thorough and continuous 2. 3.
moist condition should be
maintained by sprinkling water. The surface must be covered with 50 mm layer of earth or sand and maintained in moist condition. The surface is applied wittr asphalt mernbrane of the type and quantity approved bythe Highway agency.
Item 204 Portland Cement Stabilized Road Mix
Mixture Proportion. The amounl of asphalt material to be added to the aggregate should be from 4 to 7 mass percent ofthe dry aggregate.
Item 206 Portland Cement Treated Plant Mix Base Course
A) Travel Plant Mixing Method: The salvage or new aggregate is pulverized until at least 80 mass percent of all the materials other than stone or gravel es a 4.75 mm (No. 4) sieve. Any material retained on a 50 mm (2") sieve and other unsuitable materials are removed.
Procedure:
l. 2.
Base Course This item consist of a foundation for surface course composed of soil aggregate, Portland cement and water, proper proportions of road-mixed placed on a prepared sub-grade or subbase.
Proportioning Mixture
l. 2.
The amount of cement added to the aggregate shall be 6
to
ofthe dry aggregate. Construction requirement and procedures is the same as that of Item-203 wherein the world lime is deieted and replaced with Portland cement. 10 mass percent
Item 205 Asphalt Stabilized Road Mixed Base Course Materials. Asphalt materials should be Anionic or Cationic Emulsion asphalt of the slow setting type. 234
3. 4.
Aggregates to be treated, is placed in uniform windrow spreaded to a uniform thickness to the required depth. Portland cement of proper quantity is applied uniformly in a trench on top of the windrows or spreaded uniformly over the aggregates.
Mixing is done by rnachine for thorough and uniform blended mixture. When this method is used, a maximum time of 2 hours is allowed for wet mixing, letdown and finishing.
B) Central Plant Mixing Method. The plant is equipped with feeding and metering devices that will introduce the cement aggregate and water into the mixer in quantities specified. Mixrng continue until after a uniform mixture is attained.
C)
Spreading, Compacting and Finishing. Not more than 60 minutes should elapse from the start of mixrng to compaction of the laid mixture. After spreading, the mixture is compacted and finished in accordance with the procedures as enumerated for lime stabilized road mix base course ltern 2'3.
7-6 Clearing and Grubbing 235
Elements of Roads and l{ighw*ys Clearing and Grubbing is categorized uneler ltem-100 of the
DPWH standard specifications. It consists of clearing, grubbing, removrrg and disposing of all vegetable matter and debris except those objects that are designated to remain in place or are to be removed in consonance with other provisions of the specifications. It also includes preservation from injury or defacement of all objects designated to remain.
Specifications for Clearing and Grubbing provides that:
1. All surface objects and all trees, stumps, roots and other protruding obstructions, not designated to remain should be cleared and/or grubbed including the mowing required as follows:
a)
Removal of undisturbed stumps and roots and non-perishable solid objects with a minimum depth of 90 centimeters below sub-grade or slope of embankrnents will not be required. b) Outside the grading limits of cut and embankment areas, stumps and non perishable solid objects should be cut off not more than 15 cm" above the ground line or below low water level. c) In areas to be rounded at the top of cut slope, stumps should be cut off flush with or below the surface ofthe final 5lope line. d) Grubbing of pits, channel changes and ditches will be required only to the depth necessary by the proposed excavation with such areas. e) Buming should be under constant care of competent watchman that the surrounding vegetation, adjacent property, or anything designated to remain on the right of way will not be jeopardized. Methods of Measurement
l.
Area Basis
-
by hectare and fractions thereof acceptably cleared and prubbed.
Constructing the Roadbed
2.
Lump Sum Basis. No measurement of area will be made for this item. 3. Individual Unit Basis (selective clearing). The diameter of trees will be measured at a height of 1.4 meters above the ground. Trees less than 15 cm. diameter will not be measured for payment. The unit basis will be designated and measured in accordance with the following schedule of sizes: Diameter at heigtrt 1.4 meters Over 15 cm. to 90 cm Over 90 cm.
- Pay item designated. - Small
-Large
7-7 Excavati0n Excavation is the process of loosening and removing earth or rock from its original position in a cut and transporting it to a fill or to waste deposit. Roadway excavation is classified into:
L 2. 3. 4. 5.
Unclassified excavation Rock excavation Common excavation Muck excavation
Borrowexcavation
UnclassiJied Excavation is the excavation and disposal of all materials regardless of its nature, or not classified and rncluded in the Bill of Quantities under other pay iterns.
Rock Excavation consists of igneous, sedimentary
and
metamorphic rocks that cannot be excavated without blasting or the use ofrippers and all boulders or other dstached stones each having a volume of I cubic meter.
Common Excavations are those that are not included in the Bill of Quotations under rock excavation or other pay items. Muck Excavations consist of the removal and disoosal of
I
236
237
Constructing the Roadbed
Elements of Roads and HighwaYs
l. Embankment Sub grade Shoulders
deposits of saturated or unsaturated mixtures of soils and organic matter not suitable for foundation matenals regardless of
2. 3.
moisture contents.
Borrow Excavation is the excavation and utilization of approved materials for the construction of embankment or for other portions of the work obtained from approved sources in accordance with the following requirements:
l.
Borrow Case -I: Materials obtained from sources designated on the plans or in the special provisions.
2.
Borrow Case
- 2:
Materials obtained from sources pro-
vided by the contractor.
Construction Requirements
l. '
When there is evidence of discrepancies between the actual elevations and that shown on the plans, a preconstruction survey with reference to the datum plane used in the approved plan is undertaken by the contractor or agency to serve as basis for the computation of the actual volume excavated.
2. All excavations
should be finished to smooth and uniform surface. As much as possible, no materials shall be turned to waste. Materials outside the limits of slope should not be disturbed by the excavation operations. Excavations should be done only after the clearing and grubbing in the
3.
area.
Top soil encountered in excavation and on areas where embankment is to be placed should be removed to the depth as the Engineer may determine and should be transported and deposited in storage pile designated area separated from other excavated materials for later use.
4. Slope 5. Bedding 6. Backfillforstructures
All
unsuitable materials that could not be properly compacted in embankment must be disposed of without delay for it might be included in the work when the engineer turn his back for a cup of coffee. Borrow materials should not be placed until after the fill accessible roadway excavation has been placed in the
fill.
Pre-Watering and Pre-splitting Excavation areas and borrow pits may be pre-watered before excavation. When pre-watering is adopted, the areas to be excavated shall be moistened to the frrll depth from the surface to the bottom of the excavation. The water must be controlled so that excavated materials will contain the acceptable moisture content to permit compaction to the desired density. Pre-watering has to be supplemented where necessary by truck watering unit to insure ttrat the enrbankmert materials contains the proper moisture at the time of compaction.
Pre-Splitting is drilling and blasting procedure that may be employed to control over break and to give a uniform face to the back slope or rock cuts. Pre-Splitting is performed by:
l. 2.
Drilling holes at uniform intervals along the slope line. Loading and stemming the holes with appropriate explo-
. sives and stemming materials.
3.
Detonating the holes simultaneously.
If the pre-splitting is under contract, prior to drilling operations, the contractor shall:
The Use of Excavated Materials
All
suitable materials removed from the excavation area are used in the formation of:
238
l.
Furnish the engineer a plan outlining ttre position of all explosive to be
drill holes, depth of drilling type and
used, loading pattern and sequence of firing.
239
Elements of Roads and Highways
2. 3. 4. 5.
6.
7. 8.
The drilling and blasting plan is for record purposes only, and will not absolve the contractor of his responsibility for using proper drilling and blasting procedures. Controlled blasting must begin with a short test section of length to be approved by the engineer. The test section shall be pre-splitted production drilled and blasted. Sufficient materials sample to be taken for ttre engineer to determine if the contractor's method is satisfactory.
The holes are charged with explosives of the size, kind, strength, and spacing suitable for the formation being presplitted, and with stemming material which es a 3 inches standard sieve which has the qualities for proper confinement of the explosives. The finished pre-split slope should be reasonably uniform and free of loose rocks. Variance from the true plane of the excavated back-slope should not exceed 30 centimeters. Localized irregularities or surface variations that do not constitute safety hazard or impairment to drainage courses or facilities will be permiued. The maximum offset of 60 centimeters will be permitted for construction working bench at the bottom of each lift for use in drilling the next lower pre-splitting pattem. The engineer may order discontinuance of ttre presplitting when the materials encountered are unsuitable for pre-splitting
7-8 Free Haul
-
Overhaul (Item 107)
Free haul distance is the specified distance wherein an excavated material will be hauled without additional cost. The free haul distance is 600 meters unless otherwise specified in the contract. The overhaul is an authorized hauling in excess of the free haul distance. For example, if the hauling distance of materials is 800 meters, considering that the free haul is 600 meters, t}ren the excess 200 meters is considered the overhaul. 240
Constructing the Roadbed
Methods of Measurement The overhaul distance for material obtained and placed within the rnadway limits will be measured along the centerline of the roadway. No allowance will be made for transverse of lateral movement to or from the c.enterline except materials moved to or from designated areas outside the roadway limits.
If the contractor chooses to haul materials frorn other route which is longer than the designated source, pa)ment will be based on the overhaul distance measured along the route designaled by the engineer. Payment will be made based on the number of cubic meters overhaul materials multiplied by the overhaul distance in kilometers.
7-9 Construction of Fills and Embankment An stable embarkment is atfained by spreading the materials into a thin layer then compacted at a moisture content closer to optimum. These layered process of compaction produces unifo.*rty and higher density of the material and moisture corrtent. On the other hand, filhng materials which are just durnped in thick layers even if compacted will have a varyrng density and moisture contents from one spot to another. This will result to differential settlement or swell between the adjacent areas of the embankment.
The AASHTO-ARBA t Commiuee on Compaclion of Earthwork proposed the following amendment to the original AASFIIO density requirements to wit:
1.
2. 3.
Granular aggregates or those with only slight degree of plasticity, should be compactedto 95%-100% Fine grained aggregate possessing a low degree of plasticity is compacted to approximately 100% at a moisture content near laboratory optimum. Densities for asgregate possessing moderate to high plasticity should not be so high as to lead to subsequent srvel241
Elements of Roads and Highways
Constructing the Roadbed
ling. Compacting procedures should not exceed the as_ gregate shear strength
4.
Clay soil should not be over. compacted beyond about 90Yo
to avoid post construction swelling.
The problems encountered in the control of embanlanent
construction are:
I.
Embankment Control Basically, there are two procedures employed
to
assure
w-ater.
specifi ed embankment density.
L
To specify the expected value to the minimum acceptable amount of relative compaction and to ascertain from the
fill density tests that the specified value is obtained. To specify tJre manner and methods of constructing the embankment particularly the layer thickness, moisture control and the number of es by a roller of specified
2.
type and weight.
2.
J.
a) c)
TABLE 7-6 RECOMMENDED MINTMUM REQUTREMENTS
of Soils AASHTO M-I45 A-1, A-3 A-2-4, A-2-5 A-2-6, A-2-7
A-4, A-5, A-6, A-7 Source: AASHTO M-57-64
r
** +
Compaction at 95% of T-99 optimum content. Usc of these materials rcquircs spccial design and construction. AASHTO Desig. M-146 basement soil compacted doil.
Density test requirements
b) Moisture control
1. Mrnimum Relative Density Requirements* +
c) Evaporation or rainfall during compaction. Some soil may not easily assimilate watei unless wefiing agent is employed, Sometimes soil type cannot be segre_ gated dunng construction unless brought to laboratory. Materials re hauled from different sources and segrega_ tion of the same type is difficult in the actual work.
Construction Requirements and Equipment
Field control is a matter of ascertaining and defining the specific procedures to be done. what is important is the manner and methods that will yield the expected result.
Class
Difliculties in maintaining uniform moisture content. This is due to: a) Variable wetness of the soil. b) Problems in evenly distributing and mixing in
2.
Compaction equipment like:
Tamping Roller varies from light unit test weight 6,000 to 10,000 lbs. for an 8ft width. For giant fully loaded roller, 75,000lbs for a l0 ft. width. Grid Rollers is effective in breaking down clods and soft
rock. 3. gPneumatic Tire Roller with rubber tires, weighing g tons or more. 200 tons for airport. Smooth Tired Roller of two or three-wheeled type used to compact bases and bituminous surface.
4.
5. 6.
Wbratory Compactor is effective in compactrng stones of
Macadam road. Hauling and Spreading equipment.
Embankment on Swampy Areas Conventional construction of roadways in swampy area is
242
243
Elements of R.oads and flighways
Constructing the Roadbed
not advisable because record shows that muck turd plate provide unstable for fills causing failure of highways and railroads. Construction of roadway through swampy area requires either of the following methods:
the muck speeding up :onsolidation. care should be exercised not to exceed the shearing strength of the muck otherwise, displacement of the muck and settlernent of the fill may take place. After a period of consolidation, the surcharge material is ,emoved and rq:laced with base course and temporary pavement.
l" 2.
Removal and replacement of unsuitable materials. Displacement under the followrng methods:
a) Surcharging method b) Vertical sand drain c) Fabric reinforcement
Affit
reduetion
Removal and Replacement Method is applicable where the unstable material is shallow or thin. Unstable materials are removed to the level of the underlying materials before fillmg.
Displacement Method. Imported materials are carefully placed along the advancing slope allowed to flow under the dense muck to displace it. Sometrmes a trench almost equal to the width of the embankment may 6e blasted out and backfilled at once with stable materials. The blast pushes part of the muck out of the trench and the other portion is liquified for easy displacement. Where muck is deeper or thick, the under-fill method of displacement is applied. The trench is bladted and a large volume of the fillmaterial is dropped to settle into the peak.
The Vertical Sand Drain Method provides rapid consolidation of deep layer muck. sand drains are vertical columns of sand that penetrate the muck almost to solid materials. Across this top is a horizontal blanket extending through the side slope of the fill. u'der the pressure induced by fill and surcharg", .ob surface water flows up the clrain and out of the fill. Rapid consolidation of the muck follor,i's.
The Fabric Reinforcement Method is covering the muck with permeable fabrics. Weight Reduction Method is installing a block of styro-
foam over the muck to reduce the weight of the fill.
DPWH Specifications on Embankment (Item-104) Embankrnent shall be constructed fined as:
acceptable that could be compacted in accordance with the contract as specified. Selected Borrow for topping. Soils graded particles that es a 75 mm (3") sieve square openings and not more than 15 mass percent will the 0.075 mm (No. 200) sieve. The material shall have a Plastic lndex not more than 6 and liquid limit not more than 30.
The Relief Method is also employed after the fill materials are dumped in place. Relief ditches are blasted along the side of the fill to displace the underlying muck.
244
de-
l. Suitoble Materials are materials
,,,,:
Surcharging Method is applied on low fill over shallow muck up to 30 or 40 centimeters depth. Where top of the muck is soft, displacement through careful filling is done. The fill is then built-up in compacted layers to its elevation allowing settlement to its final grade. Surcharge of un-compacted fill material is laid to add weight and accelerate the flow of water from
of suitable materials
2.
Unstabile Materials are materials other than suitable ma-
terials such as:
a)
Materials containing detrimental quantities of organic substances like grass, roots and sewage. 245
Constructing the Roadbed
Elements of Roads and Highways
b) c) d) e)
Highly organic soils like peat and muck. Soils with liquid limit exceeding 80 and or plastic index exceeding 55. Soils with natural water content exceeding I00yo Soils with very low natural density of 800 kg./^t or lower.
Methods of Construction
l.
Z.
Where embankment lower than 120 centimeters below the sub-grade is to be made, all s,rds and vegetable matters are removed from the surface" The cleared surface should be totally broken-up by plowing, scariffing or steeprng to a minimum depth of 15 centimeters. Sods not required for removal should be disc harrowed or scarified
4.
compaction.
Compaction The contractor shall carry out full-scale compaction trials on l0 meters wide and 50 meters long. Compac-
areas not less than
tion trials with the main types of fill materials to e used in the work should be completed before any work with the corresponding rnaterials is allowed to start. Throughout the period of compaction, the contractor should adherg to the compaction procedures found during the compac-
tion trials for each type of materials, comp4ction equiprnent employed, and each degree of compaction specified.
Roadway embankment on earth materials are placed in horizontal layers not exceeding 20 centimeters loose volume than compacted as specified before the next layer is
Protection of Roadbed During Construction.
When excavated materials contains more than 25 mass percent of rock larger than 15 centimeters in greatest diameter and cannot be placed in layers of the thickness prescribed without crushing, pulverizing or further breaking down into pieces, such materials may be placed on the embankment in layers not exceeding in thickness the approximate average size ofthe larger rocks bul not greater than 60 centimeters.
Lifts of materials containing more than 25 mass percent of rock larger than 15 centimeters in greatest dimension should not be constructed above an elevation of 30 centimsters below the finished sub-grade. The balance of embankrnent should be composed of suitable matenal placed in layers not exceeding 20 centimeters in loose thickness and compacted as specified for embankment.
246
Hauling and leveling equipment should be routed and distributed over each layer of the fill to make use of compaction efforts affording and to minirnize rutting and uneven
befbre thc construction of embankment.
placed.
3.
5.
During the construction of roadway, the roadbed should be rvell maintained and drained at all times. slide ditches or gutters emptying from cuts to embankrnent or otherwise should be constructed to avoid damages to embankment by erosion.
Rounding and Warping Slope Rounding. Except solid rocks, the top and bottom of all slopes including the slopes of drainage, ditches, are rounded as planned. A layer ofearth overlapping rock is rounded above as was done in earth slope.
Warping. Adjusfinent in slopes are made to avoid injury to of weather head rock or to harmonize with, existing landscape features adjusting to thd gradual slope. At the intersections of cuts and fills, slope are adjusted and warped to flow into each other or into the nafural ground surface without noticeable break. standurg trees or marring
),47
Elements of Roads and Highways
Constructing the Roadbed
7-10 Sub-Grade Preparation
vertical structures, roads or other structures it is important to know if the in place materials possesses the following proper-
Sub-grade preparation is categorized under ltem 105 ofthe DPW standard specifications. The sub-grade is prepared for the
ties:
1. 2.
of overlying structural layers extended to the full width of the roadway.
3.
Material Requirements
l. 2.
4. 5.
Except when the sub-grade is in rock cut, all materials below the sub-grade is leveled to a depth of 15 centimeters or more as specified to meet the requirernents of selected borrow toppings Prior to start of the sub-grade preparation, all culverts cross drains, conduits and the like including the backfill, ditches. drains and drainage outlets are thoroughly com-
These desirable features could be achieved with compacted
Highly desirable characteristics such as strengtlr, low compressibility and stability is associated with high densrty values as a result of using good materials and proper compactron.
Any type of soil may be used for structural fill provided that it does not contain organic or foreign materials that will decompose or otherwise undergo changes after it is placed.
Sub-Grade Level Tolerance The finished compacted surface ofthe sub-grade shall conform to the allowable tolerance specified as follows:
l.
Permitted variance from design
+20mm -30mm
3" Permitted surface irregularities
4. 5.
measursd by 3 meters straight edge Permitted variance from design cross-fall of camber Permitted variance from design longitudinal grade over 25 m. long
,
The water content in the soil fill has substantial effect on its stabilrty and rn the process of compaction. Fine grain silt, and clay soil, or granular soil containing fine materials are affected by vibrations due to its water contelrt. Soil that is too dry is difficult to compact and those that are too wet are difficult to spread and compacted.
+ 30mm
Generally, compacted silt is stable. It is capable of developing fairly good strength and has litfle tendency for volume change. But silt soil is difficult to compact if wet or if work is
0.5%
performed on rainy period.
+ O.lyo
7-11 Compaction and Stabilization Whether the soil is used as foundation material to a40 Ln0
The soil must be durable and save against deterioration. The soil must possess proper permeability.
fill of selected types of soil properly placed and arranged.
pacted. Any work on the preparation of the sub-grade should not be allowed to start unless approved by the supervising engineer.
2. Levelof service
That, the soil must have adequate strength. The soil must be relatively incompressible to avoid insignifi cant funrre settlement. The soil must be stable against volume change as water content or other factors varv.
Compacted clay has very low permeability, an advantage where movement of water needs to be restricted, but clay soils cannot be compacted properiy when wst. If the height of the fill is reasonably high, marginal materials to be placed under water
should consist
of
coarsc granular materials. Fine grain soil
should be avoided.
249
Elements of Roads and Highways
Constructing the Roadbed
The thic}ness of the initial fill should be greater than the normal fill in order to create a working pad capable of ing equipment used for the subsequent placement and compaction of the fill.
particles tend
Equipment for Compaction
rangement.
l.
2. 3.
4.
The Pneumatic or nrbber tired rollers.
The drum type roller with projecting feet or logs called the sheep's foot roller. Vibratory compaciors. Smooth
This natural frequency refers to the value at which the soil to oscillate in unison giving maximum effect to the repeated impact imposed by the compactor instead of having a random oscillation of particles that would create damping effect. Thus, shaking the particles into a more compacted arThe Smooth Drum Roller has limited depth of compaction' This is not suited for compacting earthfill due to the size of the drum and the large soil . This $pe can be utilized for compacing limited thickness such as granular base course on highways and the like.
'Ihe hteumatic Tire Roller can be used effectively on all types of soils. It compacts by kneading available as selfpropelled unit or as towed units. Load sizes vary from 20 tons to 200 tons of which, 50 tons is commonly used.
The smooth drum roller can be used on earth moving projects to seal the surface of the fill at the end of each workday providing smooth surface for the water to rapidly run-off fiom the work area.
Light rollers of 20 tons type can compact 6 inches thick layer with few es. The 40 to 50 tons roller can compact 12 inches thick layer with 3 to 4 es. The heavy 200 tons type was proven to compact layers up to 18 inches thick with limited number of es.
Compaction Equipment and Density Control Strips
Tlre Sheep's Foot Roller is limited to cohesive soils. Its pressure varies from 700 lN/m'?
6
4,200ld\f/m'?.
The Vibratory Compadar is the most effective compactor on non-cohesive soils available as:
1.
2. 3.
Vibrating drumtype. Vibrating pnzumatic tire. Vibratfug plate equipment.
On some vibratory compactors, the vibrating frequency can be varied by operation. The frequency riurges between 1500 and 2,500 cycles per minute that is within the natural frequencies of most soil. 250
Compaction equipment should be capable of obtaining compaction requirements without detrimentally affecting the compacted materials. The compacting unit may be of any type, provided that they are capable of compacting each lift of material as specified and meet the minimum requirements.
Minimum Requirements for Road Roller
l. 2. 3.
Pneumatic Tire Roller must have smooth thread tires of equal size that will provide uniform compacting pressure for the full width of the roller and capable of exerting ground pressure ofat least 550 kN ( psi). Sheepfoot Tamping as grid roller should be capable of exerting a force of 45 Newton per millimeter (250 psi) of length of roller. Vibratory Steel Wheel Roller must have a minimum mass of 6 tons. The compactor is equipped with amplitude and frequencY controls. 251
Elements of Roads and llighways
4.
Steel Wheel Roller. Other than vibrato{, should be capable of exerting a force not less than 45 Newton per milli meter of width of the compression roll or rolls.
CHAPTER
TABLE 7.7 SOIL COMPACTION CIHRACTERISTICS
CONCRETE PAVEMENT
AND RECOMMENDED COMPACTION EQTIIPMENT Gcneral Soil Description Sand
&
sand
Gravel mixturc (no silt or clay) Sand or SAnd
uninei soit
Compaction
Classification
Charactcristics
Sa, SP,
Gw
Good
8-1 Portland Cement
Equipmcnt
Vibratory down roller Vibratory rubbcr tire or pneumatic tire cquipment
Sm,GM
Good
Gravel with
Clay
silt
:ndcd Compaction
ML
Good !o Poor
Vibratory down roller Vibratory rubber tirc, Vibratory sheep's foot
Fair to Poor
fmt
CL
Good to Fair
Pncumatic tirc, shc's foot, vibr8tory sheep's foot and rubber tire.
CH Organic Soil
OI,OH,PT
Fair to Poor
The different types
-do-
Not recommended for strrrctural carthfill
Portland cement specified by
1.
Type 1 or 1A (Air entraining). This type of cement is for general concrete construction when the specified properties ofthe other four types are not required.
2.
Type II or IIA (Air entraining) This type is for general concrete construction exposed to moderate action or where moderate heat of hydration is required.
3.
Type
III
or IIIA (Air entraining) This type is for high
strength concrete.
4. Type IV is for low heat of hydration. 5. Type V for high sulfate resistance Generally, Portland cement constitute the following chemicals:
l.
2. 3. 4. 252
of
AASFITO are the following:
Pneumatic tire,
Vibratory rubber tirc Vibratory sheep's foot sheep foot typc
Clay
substances.
Pneumatic Tire Vibratory rubbcr tirc,
Vibratory she's MH
Portland cement is a combination of limestone, marl or other calcareous materials and clay, shale, or like argillaceous
Tricalcium Silicate (C3S) Dicalcium Silicate (C2S) TricalciumAluminate (C3A) Tetracalcium Alumina Ferrite (C4AF) 253
Elements of R.oads and Highways TABLE
AND STRENGTH CHARACTERISTICS OF VARIOUS TYPES OF PORTLAND CEMENT
Types ofCement
Comp. Strength Normal Portland Cement Concrete
Compor.rnd Percent
r7283 I
Concrete Pavement Design Assumes the Following Considerations:
8-I COMPOSITION
Cornpound
II
Concrete Pavement
- Normal - Modit'ied
III - High Early IV - Low Heat V - Sulfate Resistant
50 24 lt 4233 5 60139 26 50 5 40404
100
100
75
85
8
190
120
t2 9
55
r))
55
lJ
That, transverse cracks on the concrete pavement cannot be avoided. The designer however, presumes that pavement cracks could be controlled, by providing reinforcements to the slab ts with the following assumptions.
2,
day days days
8
beams.
Percent
C3S C2S C3A CAAF
l3
L That, the pavernent slab was designed as plain concrete
100
90
110
75 75
months 100 100 100
a) With reinforeemen! cracks on the slab will be
t00 100
b) 8-2 Concrete Pavement Characteristics and Behavior
c)
The behavior of concrete pavement that is exposed to loading and environmental effect entirely depends upon the quallty of concrete, the underlying sub grade, and the base course. Generally, concrete is strong in resisting compression load acting on it, but considerably weak in resisting tensile stresses. Thus, concrete pavement actrng as a berrm, resting on a weak sub-grade and base courses, is also weak in carrying heavy load associated with impact forces. The reaction and movement of the sub-grade ing the slab, affects the stability of the concrete pavement.
Concrete like other materials also expand and contract due to temperature changes. It expands when wet and contracts when dried. After pouring, concrete shrinks as the mortar hardens and the cement hydrates. Concrete pavement changes in
length with time of day for being exposed to different elements of weather changes. A curl tendency is very likely due to the effect of daily and seasonal temperature and moisture differences between the top and bottom of the slab. 254
'
conlined to a weakened plain ts spaced at 4.50 to 6.00 msters distance. Vertical offsetting across the narrow cracks will be prevented by aggregate interlock, or by dowel bars.
Wrth simply reinforced slab, cracks will only appear at weakened plane ts spaced at 12 ta 20 meters intervals. Hair cracks to be hetd tigldy by the steel between ts.
ts are omitted. Hair cracks are checked by the steel and developed at close intervals. Faulting is countered by aggregatn interlock and
d) With continuous reinforcemen! transverse
e)
steel bars.
That longitudinal cracks on the pavement slab more than one lane wide is inevitable.
4.
Pavement slab is ed by foun
Definition of Deterioration. Deterioration of concrete pavement is due to stress brought about by load, moisture and temperature.
255
Elements of Roads and Highways
Concrete Pavement
Distress of Concrete is generally grouped intcr the following categories: a) Distortion b) Cracking c) Disintegration
Distortion is a vertical displacement of concrete slab at the ts or cracks. Distortion is due to failure or weakness of concrete ts.
Faulting. For faulting to occur, there must be free water on top of the base corrse and pavement deflection across the t due to hearry axle loads. Faulting is the result of'pumping tremendous force or load that develop urder pavement. Causes
offaulting are:
a) Loss ofslab b) Erosion of sub base
Cracking can take many forms in concrete pavement that could be the result from; applied load, temperqture or moisture changes.
The most common type of cracks are:
a) b)
Corner craclcs associated with excessive corner deflection Transverse craclcs associated with mixture or temperature stresses, or poor construction methods.
Disintegration appears in the form of durability cracking, scaling or spalling, as the result of mix design or construction related problems like: a) Durability Crachng. Results from freeze-thaw action. b) Scaling. A network of shallow fine hairline cracks which extend through the upper surface ofthe concrete. This is
the result from deicing salts, improper
construction,
freeze-thaw cycle, or steel reinforcement too closed to the surface.
2\6
c)
Spalling is the breaking or chipping of the t edges. It is the result from excessive stresses at t, weak concrete, poorly designed or constructed ts
Changes in Temperature and Moisture Content create slab curling, flexure stresses and overall lengthening and shortening of the slabs. The tendency of the slab to ,shorten is due to temperature drop or drying that create tensile stresses" On the other hand, the tendency to lengthen is due to temperature rise or increased in moisture that creates compression stresses.
8-3 Control of Cracks Load transfer anci t alignment is sometimes dependent solely on aggregate interlockrng. If the t opening is considerably small from .03 to .04 inch, the projecting aggregate is considered tightly keyed, and w'hen the edge of one slab deflects due to load. the ading edge will also be forced down. the ts open so wide, the aggregate interlocked is considered ineffective as a means of load transfer. Although some ageniies employed designs based on aggregate interlocked, others adopted the use of steel dowels as load transfer devices at the pavement ts.
If the coarse aggregates are weak, as when
Dowels can be painted, greased or coated with asphalt for almost one half of their length to break the bond with concrete, allowing the dowels to slip within one of the abutting slab ends. Skewed fiansverse contraction t in plain concrete pavement is being adopted. ts are slanted 60 centimeters in each 3.60 meters lance from the normal position. The offset places the inside of a double tire of a truck just forward of the t and at the same time the outside wheels are just behind the t.
8-4 Transverse Expansion ts Expansron ts provide space allowance for the lengthen251
Elements of Roads and Highways
Concrete Pavement
ing of slab due to expansion. Because of the so many buckling upward of concrete pavement, Engineers have come up with a conclusion that these blowups serves as conclusive evidence that expansion t is necessary,
Since year 1940, the provision for expansion t at interval of 30 meters or less was almost universally practiced in load building. The reason for providing expansion t is to prevent blowups by relieving direct compressive stresses before reaching the stage of unmanageable level.
TABLE 8-2 RTCOMMENDED DTMENSTONS OF DOWELS FOR CONCRETE PAVEMENT TS Dowel Diameter
Dowel Length
Dowel Spacing
Thickness cm.
mm
meter
mgter
15.0
20
.45
.30
17.5
25 25
.45
.30
20.0
.45
.30
2.2.5
32
.45
.30
25.0
32
.45
.30
27.5
32
.45
.30
.45
.30
Pavement
30.0 Source
:
AASHTO lnterior Guide & Proposed Revision 1980 (c) Longitudinal t
(a) Contraction t
T-
Based on the shrdies of more than 5,000 blowup samples, it was found out that blowups occurred mostly in mid afternoon at a temperature above 90"F during a peiod preceded by varying amount of precipitatrons.
8'5 Longitudinal ts Longitudmal ts are provided between adjacent traffic lanes. It is considered as hinges to provide edge , but allows rotation between the slabs" By this t, flexural stresses that might cause irregular cracks along the length of the road are relieved or neutralized. Longitudinal ts cannot be considered as a major problem under the followrng assumpttons:
1. 2.
Thatthere is no big load transfer across it. That, the expansion and contraction movement developed across the pavement width is very small small.
T
J Sawed or forrmed groove
Load transfer if specified
Longltudhd Jcllt Deformed tie oar
Formed groove
;+1.-W
+ 114min
(b) Expansion t F|GURE
258
(d) Construction t
8-1 BASIC TYPE OF CONCRETE PAVEMENT TS
FIGIJRE 8.2 LONGITUDINALT LOAD TRANSFER 2-i9
Elements of Roads and Highways
3. 4. 5. 6.
Concrete Pavement
When lanes are constructed at different time using side forms, the ts are provided with key way in the first slab to accept load transfer. For longitudinal t, deformed tie bars are used because the purpose is to hold the slabs tightly together, rather to allow the ts to open and close. The diameter and spacing of tie bars are based on the force needed to pull the narrow pavement slab over the sub-grade to the jornt. The length of tie bar is determined from the ernbedment irrside the concrete necessary to develop the strength of the bar.
&
Working
Pavement
Stress
Thickness
Grade Steel Grade 40
expand and
fill the space completely.
8-7 Reinforcement of ts Steel reinforcement for ooncrete pavement ts are specified in the design to prevent the widening of cracks produeed by shrinkage or thermal contraction.
BARS FOR LONGITUDINAL TABLE E.3 RECOIVIM"*'O ''' 3.60I}I. LANE WIDTH TS IN CONCRETE PAVEMENT Type
ving and air blown asphalt sometimes mixed with mineral filler, rubber asphalt, and various rubber compounds. They are poured hot and stiff, then cooled, others are placed cold. There are some pre-formed sealant made of strips of extruded neoprene compressed for insertion into the groove ts, the sealant will
lD" Bar Diameter 5/8" Bar Diameter Length Maximum Lcngfh Maximum
psi
cm.
meter
30,000
l5
.60
1.20
Spacine m.
m. .75
S
1.20
Billet or
20
.60
1.00
.t)
r.20
Axle Steel
25
.60
.80
,75
1.20
The rernforcement holds the fractured faces in rigid preserving the aggregate interlock and the intrusion of dirt or water. These reinforcing bars however, is not intended to resist flexural stress being produced by loads or curling.
The reinforcing steel bars are mounted in one layer along the middepth of the slab. The formula used in deg this reinforcement for conirete slab t is:
As= Lfw 2S
8-6 Construction t If
will be interrupted for quite some time that cold joirat will be inevitable, the practice is to provide a transverse construction ts. Deformed tie bars are used to hold the t tightly closed together. However, if the construction t replaces a contraction t, the use of dowels is the concrete pouring
alternative. Construction ts and cracks should be cleaned and sealed prevent infiltration of rvater to the sub-grade and to keep dirt to out of the ts. Materials fbr such purpose includes harder pa260
where:
As= I_ L_ fr-
S_
Area ofstqel cross section per foot ofslab. Length of slab between ts in feet. Coefficient of friction between the slab and the sub-grade called the coefficient of sub-grade resistance ranging from I to 2 with 1.5 recommended by AASHTO Interim Guide. Working stress in the reinforcing steel in pounds per sq. in. AASHTO Interim Guide suggested working stress from 30,000 to 45,000 psi depending upon the type and grade of steel. 201
Concrete Pavement
Elements of Roads and Highways Weldpd wire fabrics are also used as reinforcement for concrete pavement made from cold drawn steel wires having the foll
gressive.
:
Minimum allowed tensile strensth Yield strength Reinforcing bars of billet, rail or axle steel yield strength among them from
80,000 psi 70,000
Pumping is minimal, where *,he sub grade had been constructed resistant to erosion by cement or bituminous treatnent, or when the pavement slab is underlain by proper$ graded granular materials.
40,000 to 75,000
8-8 The Sub-Grade and Sub-Base for Concrete
Pavement
.
The construction standard for sub-grade and embankment are precise and almost typical for ali pavement types. Under the concrete pa'vement literature, the under coulse of selected material is always irnposed upon between the sub-grade or embankment and the concrete slab. The AASHTO Interim Guides, recommend that the subbase must be extended from 30 to 60 centimeters outside the pavement cd,ge to serve as an edge . For +"he heaviest traveled facilities, a treated cement asphalt sub-base is recommended because it increases the fatisue life and reduces ioint failure.
lhe wide acceptance of stabilizing the sub-base with Portland cement concrete pavernent is due to the investigation result of pumping of concrete slab. Pumping is the ejection of water and sub-grade soil through ts and cracks along the edges of the concrete pavement. the A repeated depression ofpavementts by heavy axle load is tJre activating factor in pumping. With the presence of water on the sub-grade and churning it with the soil, activates the fluid forming slurry that expel to the surface. A continued punrping by heavy axle load will flush the soil frorn beneath the pavement to the effected locations. Failure of the t v,,ill be noticed followed by transverse cracking 2{i2
or breaking of comers. One crack will invite more chances for pumping action, t failures and by cracking that will be pro-
Despite the continued studies, researches and experimental development made, there is no assurance for an ffictive means of excludintg free water from the under pavement ts, craclcs and edges. So far, the use of under-courses with drainage provision is being considered as the solution to prevent pumping.
8-9 Concrete Proportions The fundamental rule to obtain good concrete is the proper selection of cemerfi aggregate and water thus:
l. Type I
or II cement is specified for concrste pavement. Water for concrete must be clean, free from acids, alkali and oil. Water that is suited for drinking purposes is acceptable for mixing cement except water containing large amount of sulfate. 3. [f concrete is to be strong, sound and durable, the aggregate must have similar properties. 4. The mineral aggregate of concrete is about 75%o of the volume or about 80% of the weight of normal pavement. 5. The maximum size of coarse aggregate is 2 inches. However, the use of larger aggregates according to some experienced highway engineers increases its length and durability. This precept is ed'by reasons that, with larger aggregate, less water is needed thereby, increasing the ratio of cement to water. Under the cement water ratio principle, concrete is stronger when water content is less.
2.
263
Elements of Roads and Highways
ixture Adrnixture is a substance added in mixing to change the characteristic of concrete mixture. There are varieties of ixtures available like, lhe air-entraining ixture, which is very comrnon. Others, like water reducer, retarder, accelerator, pozzolan and plasticizer are also used.
Air Entrainment Air entrainmsnt is the entrapment of air in the concrete mixture in the form of evenly distributed small bubbles It is used to increase the concrete resistance to surface scaling caused by deicing with calcium or sodium chloride. Another working advantage of air entrainment is improving its workability and reduces bleeding in fresh concrete.
The efrectiveness of air entrainmerrt is to increase the concrete durability that is influenced by:
l. 2. 3.
Percentage of air present in the mixture. Grading of aggregates. Size and distribution of air bubbles.
Air entrainmerf in concrete may the attained by using Air Entraining Portland Cement or by Air Entraining irture added to each batch of concrete while mixins.
Concrete Pavement
Durability therefore, is dependent on the water-cement ratio that should be properly controlled to obtain richness of the paste. AASHTO Guide Specifications for highway construction established the maxirnum water cement ratio at 6 gallons per bag of cement on normal conditions and 5 % gallons per bag of cement for severe atmospheric conditions.
8-10 Concrete Mixture Considering the high cost of cernent, the objectwe in mixing concrete is to use more aggregates and as lrttle cemenl as possible, while maintaining the workability necessary for a successful pouring and consolidation.
For structural concrete poured in inaccessible small areas around reinforcing bars, it is necessary to over-fill the voids or spaces around the aggregate and reinfbrcement using a foee flowing cement in water paste forrn. On tlrc conttary, pavement where the slab is open and thin with an access to manipulate from the surface, a drier mixture can be poured inside the form with ease and success. Thus, a higher percentage of aggregate and a less fluid cement-water paste can be used.
On how to reduce the amount of cement-water paste and the cost of the mixture u'e have to:
l.
Allow the larger size of aggregate that can be accorffno-
2.
dated in the pavement slab. Ascertain the aggregate is uniformly graded from coarse
Cement and Water Ratio As mentioned earlier, the strength and other desirable properties of concrete mixture varies depending upon the ratio of concrete to mixing water. A non air-entrained concrete with a water cement ratio by weight of 5 gallons of water per bag of cr:ment may have a compressive strength of about 5,300 psi in 28 days. On the other hand, a mixture of concrete with 7 gallons of water per bag of cement has developed strength of 3.700 psi only for 28days. 264
3. 4.
to fine.
Avail of the biggest quantrty of coarse aggregate consistent with proper workability. Adopt the lowest slump consistent with the proper pouring and finishing.
For concrete pavement, the specified value of slump is 1-2 or 2-3 inches. The slump test (AASHTO T-l l9) is the old tradi265
Elements of Roads and Highways
Concrete Pavement
tional and most widely used method in determining the consistency of concrete. A truncated cone of metal sheet 12 inches high with the base and top diameters 8 inches and 4 inches respectively is filled in 3 layers with fresh concrete. Each layer is rodded 25 times. Then the cone is lifted off vertically, allowing the concrete to subside. The slump is the height in inches that the top of the specimen falls.
is determined by the trial batch method, is obtained as final proportion for mixhrre desired the after until mixture. the succeeding Concrete mixture
8-11 Polymer Concrete Polymer Concrete could be used alone or in combination aggregates together producing
with Portland cement to bind concrete.
Polymer mirture is classified into thefollowing: 1.
2.
Polymer-Impregnated Concrete (PIC) is a portland cement concrete impregnated with monomer after curing Polymer Concrete (PC) is a rnixhre of polymer binder and aggregate.
a
Polymer Cement Concrete (PCC) is a pre-mixture of cement paste and aggregate wherein a monomer is mixed before curing.
20 cm.
Polymer possesses a higher strength concrete, but due to its prohibitive cos! its use is being limited to bridge deck or repair
of spalled ts. FIGURE
8.3 SLUMP TEST
Another way of testing the consistency of concrete is by the Kelly Ball method (see ASTM C-360). The apparatus is a metal cylinder 15 centirneters diameter and 12 centimeters high with hemisphere bottom shaped weighing 14 kilograms. A graduated handle rising from the top of ball es through a metal frame that is 30 cm. apart. The ball is placed on the surface of the fresh concrete. Its penetration is measured by comparing its position with that of the frame.
8-12 Curing of Concrete Pavement Newly placed concrste pavement needs curing. Curing may be accomplished by several methods but basically; all the methods could be categoized into two:
l.
Those that keep the surface constantly wet or cover it with water absorbent material that is re-wetted from time to
time. that pavement evaporated from the water already in the concrete which is retained is sufficient enough for hydration.
2. Those The advantage of Kelly Ball method is that reading could be taken immediately on the concrete being poured on the roadway. On the contrary, the slump test requires more time but could be conducted only on selected samples" 266
The chemical action between cement and water produces 267
Elements of Roads anC Highways
Concrete Pavernent
strength of concrete. If the concrete dries rut quickly, hydration and strength process will stop, but when moisture becomes available during hydration, strength gain will continue.
It
ties. 2.
Rapid dryrng of fresh concrete will result to surface crazing or cracking. Under extrerne hot weather or dry winds, severe cracking will eventually occur. The shortest period of curing for normal concrete is 5 days according to AASFITO recommendation.
Concrete pavemant is categorized under item 3l standard specifications, which provides that.
I
of DPWI{
Fine aggregates from different sources of supply should not be mixed or stored in the same pile nor used alternately.
3.
Fine aggregates should not contain more than 3 mass percent of materials ing the 0.075 mm (No. 200 sieve) by washing nor more than one mass percent each of clay lumps or shale.
4.
The use of beach sand will not be allowed without the approval of the supervising engineer.
5.
Ifthe fine
8-13 DPWH Specilicafions on Concrete Pavement
shall be free from injurious amounts of organic impuri-
aggregate is subjected to 5 cycles or the sodium sulfate soundness test, the weighed loss should not exceed 10 mass percent.
This item shall consist of Portland cement Concrete pavement with or wrthout reinforcement, constructed on the pre-
If fine aggregrte is subjected to test for organic impurities and a color darker than the standard is produced, it should be rejected. However, when tested for the effect of organic impurities of strength or mortar by AASHTO T-7I,
pared base in accordance with the plans and specifications.
Material Requirernents: Portland cement shall conform to the applicable requirements of Item 0-700, hydraulic cement. Only fpe I Portland cement should be used. Different brands or the sarne brands from different mills shall not be mixed nor shall they be used
the fine aggregate may be used if the relative strength at 7 and 28 days is not less than 95 mass percent. TABLE 8-4 GRADING REQUIREMENTS FOR FTNE AGGREGATES Sieve Designation
alternately unless approved by fhe supervisrng engineer. Cement that for any reasons become partially hardened, or which contains lumps or caked cement including those salvaged from discarded or used bags, should not be used.
10.0 mm 3/8"
mm 1.18 mm 0.30 mm 0.15 mm
4.75
Fine Aggregates:
1.
Fine aggregate shall consist ofnatural sand, stone screening or other inert materials with similar characteristics or combination thereof, having hard strong and durable particles.
Mass Percent 100
No.4
95-100
No. 16 No. 50 No. 100
45-80 5-30
0-10
Coarse Aggregate
1.
Coarse aggregate shall consist of crushed stone, gravel, blast furnace, slag, or other approved inert materials of
268 269
Concrete Pavement
Elements'of Roads and Highways Similar character or combinations thereof, having hard, 2.
J.
4.
strong durable pieces free fr.om any adherent coatings. Coarse aggregate should contain not more than one mass percent of material ing the 0.075 mm (No. 200) sieve nor more than 0.25 mass percent of clay lumps, not more than 3.5 mass percent of soft fragments. Ifthe coarse aggregate was subjected to 5 cycle ofthe sodium sulfate soundness test, the lost weight should not exceed 12 mass percent. It should have a mass percent of wear not exceeding 40 when tested by AASHTO T-96. If slag is used, its density should not be less than I 120 kg
Per cubic meter. The gradation of the coarse aggregate should conform to table 8-5. Only one grading specification should be used from anv one source. TABLE 8-5 GRADING REQUIREMENTS FOR
Reinforcing Steel The Specifications states that: dowels and tie bars to be used in concrete pavement shall conform to the requiremants of AASFIIO M-31 or M-42 except that rail steel shall not be used for tie bars to be bended and re-straightened during construction. Specifications further provides that:
l. 2. 3. 4.
COARSE AGGREGA1IE
Tie bars shall be deformed bars. Dowels shall be plain round bars delivered to the site with on€ half of each dowel length painted with one coat of approved lead or tar paint. The sleeves of dowels shall be metal of approved design to cover 50 mm plus or minus 5 mm of the dowels, with a closed end, with a suitable stop to hold the end of the sleeve at least 25 mm from the end of the dowel. Sleeve shall be of such design that they do not collapse during construction.
Mass Percent Sieve Designation
Grading
Grading
Grading
B
c
mm
lnch
A
75.0
3"
100
63.0
2-tt2
50.0
37.5 l-l/2"
25.0 20.0 12
4.75
90-100
2" 25-60
lu 3/4"
o-io
l/2* No.4
0-5
100
roo
90-100
90-100
35-70 0-15
35-70
0-5
ro-lo 0-5
t Fillers t fillers should be mixed asphalt and mineral or rubber filler. The pre-formed t fillers are punched to adrnit the dowels. Filler for each t should be furnished in a single place for the full depth and width of the t.
Storage of Cement and Aggregate The storage house for cement should be waterproof with raised floor from the ground to protect the cemerf from rain or dampness.
Water Water to be used in concrete mixing or curing or other designated applications should be clean and free from oil, salt, acid, alkali, grass or other substances injurious to be finished product. Drinking water if used needs to be tested. 270
L
The provisions for storage should be ample enough and the shipment of cement as received is separately stored in such a manner as to allow the earliest deliveries to be used first and to provide easy access for identification and inspection of each shipment. 271
Concrete Pavement
Blements of Roads and Highways
2.
Storage house must have the capacity to accommodate suffrcient quantity of cement to allow sampling at least 12
3.
To secure uniformity of concrete mixture, the coarse aggregates are separated into two or more sizes. Different sizes of aggregates are stored in separate bins or in sepa-
Quality Control of Concrete
rate stockpiles sufficiently remote from each other to prevent the materials at the edge on the piles from becoming
fi cations provides that
concrete pavements using a minimum of 75 rnm verrtional concrete as the surface course.
days before the cement is used.
For quality control of concrete in general, the DPWH speci-
trol of all materials during the handling, blending mixing and placement operations. The contractor shall furnish the engineer a Quality Control PIan detailing the production control procedures and the type and frequency of sampling and testing to insure that the con-
Proportioning, Consistency and Strength of Concrete Prepare a design mixture based on the absolute volume method as specified in the American Concrete Institute (ACI) standard "Recommended Practice for selecting Proportion for normal and heavyweight concrete". The intent of this specification is to require approximately 9.0 bags of cement per cubic meter of concrete based on a 40kg. Weight per bag of cement. However, leaner or richer mixhrre may be used in order to meet the minimum strength requirements.
2.
The engineer will determine from{he laboratory tests The materials to be used, the cement content and the proportions of aggregate and water that will produce a wdrkable concrete having a slump of between 40 and 70 mm (1112" to 3") if not vibrated, or between 10 to 40 mm if vibrated and flexural strength of not less than 3 8 Mpa (550 psi) when tested by the third-point method or 4.5 Mpa (650 psi) when tested by the mid-point method or a compressive strength of 24.1 Mpa (3,500 psi) when tested at fourteen days.
3.
The designer should consider the use of lean concrete (econo-concrete) mixture using local materials or specifically modified convsntional concrste mixture in base course and in the lower course of compoeite, monolithio
272
:
"The contractor shall be responsiblefor the quality con-
intermixed.
l.
of con-
crete produced complies with the specifcafions. The supervising Engineer shall be provided free access to recent plant production recards, and if requested infctrmutional copies of design, materials certifcations and sampling and resting reports."
Required Qualification of Workmen Concrete Butcher - The person performing the batching or mrxing operation capable of accurately conducting aggregate surface moisture determinations and establishing correct scale weight for concrete materials. Concrete Technician - The person responsible for concrete production control and sampling and testing for quality control proficient in concrete technology having a sound knowledge of the specifications as they relate to concrete production. He shall be:
L 2.
Capable of conducting test on eoncrete and concrete materials in accordance with the specifications. Capable of adjusting concrete mix designs for improving workability emd specification compliance and preparing
trial mix design. 273
Concrete Pavement
Elements of Roads and Highways
3.
He shall be qualified to act as the concrete batcher in the absence ofthe batcher.
8-14 Equipment The equipment and tools necessary for handhng materials and performing all phase of the work shall be approved by the supervising Engineer as to design, capaclty and mechanical conditron. The equipment should be at the job site sufficiently ahead of the start of construction operations to be examined thoroughly and approved by the Engineer.
A.
B. Mixers Concrete may be mixed at the construction site, or at a central plant or wholly or in part in truck mixers under the following conditions:
l. 2.
Batching Plant Equipment
L
The batching plant should include bins, weighing hoppers and scales for the fine aggregate and for each size of coarse aggregate. The weighing hopper shall be properly
2.
The batching plant should be equipped with a suitable non-resealable batch counter, which will correctly indicate the number of batches and proportioned.
3.
Bins with adequate separate compartrnents for fine aggregate and for each size of coarse aggregate should be provided in the batching plant.
4.
4.
for weighing aggregates and cement should be of either tlre beam type or the spring less-dial type. They should be accurate within one half percent throughout the
5.
range ofuse.
6.
274
The batching plant should be equipped with automatic weighing devices of an approved type 1o proportion aggregates and bulk cement.
The mixer shall be equipped with approved timing devices, which will automatically lock the discharge lever when the drum has been charged and released at the end of the mixing period. In case of timing device failure, the mixer may be used for the balance of the day while it is being repaired, provided that each batch is mixed in 90 seconds.
Scales
Poises should be designed to be locked in any position and to prevent unauthorized change. Scales shall be inspected and sealed as often as the Engineer may deem nscessary to assure their continued accuracy.
Mixers at site of constructioz - Mixing should be done in an approved mixer capable of combining the aggregates, c"-*t and water into a thoroughly mixed and uniform mass within the specified mixing and dischargirrg and distributing the mixture without segregation on the prepared grade.
3.
sealed and vented to preclude dusting operations.
5.
Each mixer shall have a manufacturer's plate attached in a prominent place showing the capacity of the drum in of volume of mixed concrete and the speed of rotation of the mixing drum or blades.
C.
Truck mixers to be used for mixing and hauling concrste NA Truck Agitators used for hauling central mixed concrete shall conform to the requirements of AASFIIO Mr57. Non-Agitator Trucla. Bodies of non-agitating hauling equipment for concrete shall be smooth, mortar-tight metal containers capable of discharging the concrete at a satisfactory controlled rate without segregation.
Paving and Finishing EquiPment
The concrete should be placed and set with an approved paver designed to spread, consolidate, screed and float finish the freshly placed concrete in one complete of the machine in a manner that a minimum of hand finishing will be necessary 215
Concrete Pavement
Elements of Roads and Flighways
to provide a dense and
homogeneous pavement. The finishing machine should be equipped with at least two oscillating tlpe of transverse screed. Vibrator should operate at 8,300 to 9,600 frequency of impulse per minute under load at a maximum spacing of 60 centimeters.
D. Concrete Saw Cr:ncrete saw should be rvater-cooled diamond edge saw blade or an abrasive wheel conforming to the required dimensions and rate ofspeed.
If loss of densitv results from the trimming operatrons, i1 should tre restored by additional compaction before concrete is placed. If any traffic is allowed to use the prepared sub-grade or the surface. it should tre checked and corrected immediately ahead of the placing ol' concrete. The sub-grade or base should be
unifonnly moistened when the concrete is placed.
Setting of Forms
l.
grade. Any roadbed, which is below the established grade, should be filled with approved gramrlar materials to grade in lifts of three centimeters or less, and thoroughly re-rolled or tarnped. hnperfections or variations above the grade should be corrected by tamping or by
E. Forms
l. 2 3.
Forms should be made of an approved steel section with a depth equal to the thickness of the pavement at the edge. The base of the form should be of sufficient width to provide necessary stability in all directions. The flange braces must extend outward of the base not less than 2/3 of the height of form. All forms should be rigidly ed on bed during the entire operation of placing and finishing the concrete. It should be provided with adequate devices to secure its setting so that when in place, they will withstand without visible spring or settlement the impact and vibration of consolidating and finishing of the concrete pavement.
cutting as necessary.
2"
After the base or sub grade have been placed and compacted areas that will the paving machine and the grade on which the pavement is to be constructed should be trimmed to the proper elevation by means of a properly designed machine extending the work at least 60 centimeters beyond each edge of the proposed concrete pavement.
Grading ond alignment- Form shall be set suffrciently advance from the point where the concrete is being placed. After setting to correct grade, the base is thoroughly tamped, mechanically or by hand, at both edge of the form base inside and outside. The forms should not deviate from the true line by more than one centimeter at any pornt.
3.
8-15 Preparation of Grade to the required density, the
Base Suppnrl -The foundation under the forms should be hard and true to gracle, so that the form when set wili be fitmly in with its whole iength at the specified
Grading and Alignment - T"he alignment and grade elevation of the forms should be checked and corrections be made irnmediately before the placing of concrete. Prior to the placing of concrete, the crown and elevation are verified by holding an approved template in a vertical position moving backward and forward on the forms.
Conditioning the Sub grade or Base Course
l.
When the side forms have been security set to grade, the base-course should be brought to proper cross section. High areas are trirnmed to proper clevation and low areas ')"7
276
l
Elements of Roads and Highways
2.
Concrete Pavement
are filled and properly compacted. The finished grade should be maintained rn a smooth and compacted condition until the concrete is placed. Unless waterproof base course material is specified, it should be uniformly moistened when the concrete is placed. If it subsequently becomes too dry, the sub-grade or base course is sprinkled with water, but the method of sprinkling should not form mud or pools of water.
cordance with AASHTO M-157 requlremenrs, except that the minimum required revolutions at the mixing speed for transit mixed concrete may be reduced to not less than that recommended by the mixer manufbcturer. The number of revolutions recommended by the mixer manufacturer should be indicated on a serial plate at_ tached to the mixer
2.
When n,ixing is done at the site or in a central mixing plant, the mixing time should not be less than 50 secondi nor more than 90 seconds, unless mixing performance tests provide adequate mixing of the concrete in a shorter tune period. Mixing time ends when the discharge chute of the mixer opens. The contents of the rndividuil mixer drum shall be removed completely before a succeedins batch is loaded thereln
3.
The volurne of concrete mix per batch should not exceed the mixers nominal capacity in cubic meter, as indicated on the manufacturers standard rating plate attached on the mixer except that an overload up to l0 o% above the mixers normal capacity may be permitted provided that concrete test data"for strength, segregation and uniform consistency are satisfied and no spoilage of concrete
8-16 tlandling, Measuring and Batching of Materials The batching plant and equivalent layout must provide a srnooth flow of continuous supply and transport of materials to the work. Stockpiles are built up in layers of not rnore than one meter in tldckness with each layer completely in place before beginnrng the next that should not be allowed to "cone" down over the nexl lower layer.
All
washed aggregates and aggregate produced or hand,led brnned for draining at least trvelve hours before being batched.
by hydraulic methods are stockpiled or
The mixer should be charged without loss of cement and batched material should be weighed for each material required within a tolerance of one percent for cement and two percent for aggregates. Water may be measured by volume or by weight and the accuracy of measuring water shall be within a range of not more than one percent error.
should take place.
4.
The batches shall be charged into the drum with a por_ tion of the mixing water enter in advance of the cement and aggregates. The flow of water should be uniform that all water shall be inside the drum by the end of the first
l5
seconds of the mixing period.
Mixing Concrete
5.
The concrete may be mixed at the site, in a central plant or by truck mixers of approved type and capacitl'. Mixing time will be measured from the time when all the materials except water
6. Mixed concrete from the central
are already inside the drum.
l. 278
Ready mix concrete shall be mixed and delirered in ac-
The throat of the drum shall be kept free of concrete ac_ cumulatjon that may restrict the free flow of materials into the drum.
mixing plant shall be transported in truck mixers, truck agitators, or non_ agitating trucks. The time elapsed from the time water is added to the mix until the concrete is deposited in place )79
Concrete Pavernent
Elements of Roads and Highways at the site shall not exceed 45 minutes when the concrete is hauled in non-agitating trucks, nor 90 minutes when hauled in truck mixers or truck agitators. except that in hot rveather or under other conditions contributing to quick hardening of concrete, the maximum allowable time may be reduced by the supervising Engineer.
7.
constructed lane, and mechanical equipment
3.
Vibrators shoultl not be allowed to come in with a t assembly, grade or side form. In no case it be operated longerthan 15 seconds in any one location'
4.
Concrete should be deposited as near as possible to the expansion and contraction ts wilhout disturbing them, but should not be dumped from the discharge bucket or hopper into a t assembly unless the hopper is well
Re-tempering concrete by adding water or by any other means shall not be permitted, except that when concrete
is
delivered in truck mixers, additional water may be added to the batch materials and additional mixing is per-
will be oper-
ated upon the existing lane, that previously constructed lane must have attained the strength for 14 day concrete' If finishing equipment is carried on the existing lane paving in ading lanes may be permitted only after 3 days'
form increasing the slump to meet the requirements if permitted by the Engineer, provided that all these operations are performed within 45 minutes after the initial mixing operations and the water cement ration is not ex-
centered on the
t assemblY.
ceeded.
Concrete t
Limitation of Mixing
No concrete should be mixed, placed or finished, when natural light is insufficient, unless an adequate and approved artificial liglrting system is operated. 8-17 Placing or Depositing of Concrete in such a manner requiring minimal re*handling. Unless truck mixers or non-agitating hauling equipment are equipped with a means to discharge concrete rvithout segregation of the materials, the concrete should be unloaded inside the form in a manner to prevent segregation of Concrete
is
deposited
the particles.
L
2 280
Placing of concrete between transverse ts without the use of intermediate bulkheads. Necessary hand spreading shall be done with shovels, not rakes. Workers are not allowed to walk on. Where concrete is to be placed ading a previously
Concrete ts are constructed according to the type' dimensions and at the locations as indicated on plans or special provisions.
All ts should be protected from the intrusion of injurious foreign materials until after sealed. Concrete pavement ioints are classifed into:
l. 2. 3. 4. 5.
Longitudinalt Transverse t
Transverse construction t Transverse construction t
Loadtransfer device
Longitudinal t
l.
Deformed steel bars or special length, size, spacing and materials are placed perpendicular to the longitudinal ts. Tie bar should not be painted or coated with asphalt or otier materials or enclosed in tubes or sleeves' 281
Elements of Roads and l{igtrways
2.
Except those made of rail steel, tie bars maybe bent at right angles against the form of the first lane constructed and straightened into final position before the concrete of
the adjacent lane is placed.
3.
4.
Concrete Pavement
The longitudinal ts are sawed before the end of the curing period or shortly thereafter and before any equip_ ment or vehicles are allowed on the pavement. The sawed area should be thoroughly cleaned and if required the t should be filled immediately with sealer.
The tool or device remain in place at least until the concrete has attained its initial set, and to be removed without disturbing the adjacent concrete.
3.
concrete hardened sufficiently to permit sawing wilhout excessive ravelling, and the time is usually within 24 hours.
Longitudinal pavement insert type ts should be formed by placing a continuous st ip a plastic material which will react adversely with the chemical constituent ofthe concrete"
2. 3.
a)
ts are sewed before uncontrolled shrinkage
b)
cracking takes place. If necessary, the sawing operations should be car-
c)
Transverse Expansion t
l.
Sawed Contraction t is made by sawing groove in the surface of the pavement. Sawing is done as soon as the
The expansion t filler should be continuous from form to form shaped to the sub-grade and to the key_way along the form. Pre-formed t filler should be furnished in lengths equal to the pavement width or equal to the width of tt.
d) e)
lane.
Finished
t should not deviate more then 6 mm from a If t fiflers are assembled in sections.
straight line.
there should be no offsets between adjacent units. concrete should be permitted anywhere within the expansion space.
4. No plugs of
t is classified into:
l.
Transverse Strip Contraction t is installing as parting strip to be left in place as specified.
2.
Formed Groove is installed by depressing an approved tool or device into the plastic concrete.
282
weather conditions.
The sawing of any t is omiued if crack occurs at or near the t location prior to the time of sawing.
Sawing should be discontinued when crack develops ahead of the saw. In general, all ts should be sawed in sequence. If extreme condition exists making it impractical to prevent erratic cracking by early sawing, the contraction t groove is formed prior to the initial setting of concrete.
Transverse Contraction t
l.
Transverse contraction
2.
No Transverse t should be located within 1.50 meters of an expansion t, contraction ! plane or weak-
Transverse Contraction t The transverse contraction
ried on during the day or night regardless of
t is provided when there is art interruption of more than 30 minutes in the concreting operations.
ness.
has been mixed at the right time of intemrption to form a slab of al least 1.50 meters long the excess concrete from the last preceding t should be removed and disposed of as directed
3. If sufficient concrete
283
Elements of Roads and Highwtys
Concrete Pavement
Load Transfer Device
8-1S Final Consolidation and Finishing
Load transfer device is provided along the longitudinal centerline of the pavement either by tongue and groove concrete or by steel dowels under the following considerations: When dowel is used, it should be held in position parallel to the surface and centerline of the slab by a metal device that is left embedded in the pavement. 2.
J.
The portion of each dowel painted with one coat of lead or tar should be thoroughly c
The sequence of operations after placing the concrete at grade is the strike-off or consolidation, floating and removal of laitance, straight edging, and final surf,ace finishing. L Addition of water to the surface of concrete in order to assist in finishing operations should not be permitted. However, if the application of water to the surface is allowed, it should be applied as fog by means of approved sprayer equiprnent. z.
'lhe sleeves for dowel should be rnetal, design to cover 50 mm plus or minus 5 mm of the dowels with a water tight closed end with a suitable stop to hold the end of
pavement.
the sleeves at least 25 mm from the end of the dor,vel.
Concrete, adjacent to ts, should be mechanically vibrated. The finishing machine is brought forward operating in a manner to avoid damages or misalignment of
ln lieu of using dowel assemblies at contraction ts, dowels may be place in the fulI thickness of the pavement by a mechanical device approved by the Engineer.
ts. 4.
If the unintemrpted operation of finishing machine over beyond the ts causes segregation of concrete, and misalignment of the ts, the finishing machine should be stopped when the front screed is approximately 20 centimeters from the t.
5.
TABLE 8-6 RECOMMENDED DIMENSION OF'DOWEL FOR CONCRETE PAVEMENT
Centimeters
Dowel Diameter mm
15.0
20
45
30
t7.5 20.0
25 25
45 45
30 30
22.5
32
45
30
25.0
32
45
30
The front screed should be lifted and set directly on top of the t and the forward motion of the finishing machine is resumed. When the second screed is closed enough to permit the excess mortar in front of it to flow over the t, it should be lifted and carried over the
27.5 30.0
32
45
30
t
32
45
30
Pavement Thickness
Source: AASHTO
284
Dowel Length
Dowel Spacing
Centimeters
Centimeters
The concrete placed adjacent to ts shall be compacted and firmly set wilhout voids or segregation under and around the load transfer devices, t assembly units, and other features designed to extend into the
Interim Guide and proposed revision 1980
6.
Thereafter, the finishing machine may be run over the t without lifting the screeds, provided ttrat there is no 285
Concrete Pavement
Elements of Roads and Highways segregated concrete immediately between the
t and
2. In a narrow width or areas of irregular dimensions
where operations of the mechanical equipment are impractical, hand methods may be used.
the screed or on top of the t.
Finishing Machine
3.
Concrete as soon as placed is struck off and screeded by an approved portable screeder. The screed should be at least 60 cm. longer than the maximum width of the slab to be struck off.
4.
Consolidation should be attained by the use of suitable vibrator or other approved equipment.
5.
On finishing operations, the screed is moved fonrard on the forms with a combined longitudinal and transversal shearing motion.
6.
Movement is always in the direction where the work is progressing and manipulated that neither end is raised from the side forms during the striking off process. If necessary, this should be repeated until the surface is of uniform textures, true to grade and across section, free
Non-Wbratory method - The concrete is distributed and It is struck off and screened by an ap-
spread as soon as placed.
proved frnishing machine. The machine goes over each area of pavement as many times and at such intervals as necessary to give the proper compaction and leave a uniform texture surface.
l.
2.
Excessive machine operation over a given area should be avoided. The top of the forms should be kept clean by an effective device attached to the machine and the travel of the machines on forms should be maintained true to grade without wobbling or otlrer vibration tendrng to affect the precision finish.
During the first of the finishing machine, a uniform ridge of concrete should be maintained ahead of the front screed in its entire lensth.
3. If uniform and satisfactory
density of the concrete is not obtained by the vibratory method at ts along the forms of the structures, and throughout the pavement, the contractor will be required to furnish equipment and method that will produce pavement conforming to the specifications.
ofporous areas. Floating
1.
chanical method.
2.
The hand operated longitudinal float should not be less than 3.60 meters long and 15 centimeters wide properly stiffened to prevent flexibility and warping.
3.
The longitudinal float is operated from a footbridge
Hand Finishing Hand finishing methods may be used under the following conditions:
l.
286
In the event of mechanical equipment breakdown hand methods may be used to finish the concrete already deposited on the grade or form.
After the concrete has been struck off and consolidated, it is further smoothened, trued and consolidated by means of a longitudinal float, either by hand or by me-
resting on the side forms and spanning but not torrching the concrete. Working with a sawing motion while held in a floating position parallel to the road centerline, and moving gradually from one side of the pavement to the other side. 287
Elements of Roads and Highways
4.
5.
The movement ahead along the centerline of the pavement should be in successive advances of not more than one half length of the float. Any excess water or soupy material is wasted over the side forms on each .
Concrete Pavernent
Final Finish
l.
The track from where the mechanical float operates should be accurately adjusted to the required crown and
float also accurately adjusted and coordinated with the transverse finishing machine so that small amount of
Ping.
Z. "fhe brooming
operation is executed by producing uniform appearance of comrgations produced in the surf;ace not more than I 5 ryn dePth.
mortar is carried ahead of the float at all times.
6.
The float should over each area of pavement at least two times. Excessive operations over a certain area should not be permitted. Any excess water or
3.
soupy material should be wasted over the side forms on each .
Straight Edge Testing and Surface Correction
l.
After the floating work and excess water removed, while the concrete is still in plastic condition, the surface ofthe concrete is tested for correctness by a 3.00
4.
The straight edge bar is held in with the surface
in
'
3.
wi&h.
5.
Advances along the road should be in successive stages of not more than one half the length of the straight edge bar. Any depression found or noticed should be filled immediately with freshly mixed concrete, consolidated
Hand belt must have suitable handles to permit a controlled uniform manipulation. The belt is operated with short strokes transverse to the centerline with a rapid advance parallel to the centerline.
6.
If the surface texture is drag fnished, use a drag, which consists of a seamless strip of damp burlap, or cotton fabric, which will produce a uniform gritty texture after dragging it longitudinally along the full width of the
The surface across the ts must strictly meet the requirements for smootluress. The Straight Edge testing should continue until the entire surface is found to be free from humps and noticeable departures from the straight edge bars.
288
surface texture is belt finished, after straight edging and the water sheen has practically disappeared, and just before the concrete becomes non plastic, the surface is belted with a 2-ply canvas belt not less than 20 cm. wide and at least 100 cm. longer than the pavement
If the
successive positions parallel to the road centerline and the whole area gone over from one side of the slab to the other as necessary.
and finished.
4.
Brooming should be completed before the concrete is in such condition that the surface will be unduly roughened by the operations. The finished surface should be free from rough and porous areas, irregularities, and depressions, resulting from the improper handling of the broom.
meters long straiglrt edge bar.
2.
If the surface texture is broom-fnished, it should be applied when the water sheen has practically disappeared. The broom should be drawn from the center to the edge of the pavement with adjacent strokes slightly overlap-
pavement.
7.
For pavemcnt 5 meters or more in width, fhe drag is mounted on a bridge, which travel on the forms' The burlap or fabric 1.00 meter wide is in wrth the 289
Elements of Roads and Highways
Concrete Pavement
full width of the pavement surface while dragging.
8.
of more than 3 mm but not exceeding 12 mm in 3.00 meters spar is marked and immediately ground down with an approved grinding tool to an elevation where the area or spot will not show surface deviations in excess of 3 mm when tested with the 3 meters straight edge.
The drag shall consist of not less than 2 layers of burlap
with the bottom layer approximately 15 centimeter wider than the layer. It should be maintained with a resultant surface uniform in appearance free from grooves
over 1.5 mm. Drags should be maintained clean
and
free from encrusted mortar. Regardless of tlre methods used in final finishing work, the hardened surface pavement must have 0.25 coefficients of friction or more. Completed pavement found to have coefficient of friction less than 0.25 should be grounded or scored by the contra;tor at his expense to provide the required coefficient of fric-
tion.
Edging at Forms and ts
1.
2.
After the final finished, but before the concrete has taken its initial set, the pavement edges along its side of the slab and all ts, transverse construction ts, and emergency construction ts, shouid be worked with an approved tool and rounded to the radius required.
Any tool marks appearing on the slab, adjacent to the ts should be eliminated by brooming the surface. But in so doing, the rounded slab corner should not be disturbed. All concrete on top of the t fillers should be removed completely.
3.
All ts are tested with a straight edge and corrected if one edge of the t is higher than the other before the concrete completely set.
Surface Test
l. 290
2.
Where the departure ftom correct cross section exceeds 12 mm, the pavement should be removed and replaced by the contractor at his expense.
3.
Any area or section that was removed should not be less than 1.5 meters in length and not less than the full wrdth of the lane involved.
4.
When it is necessary to remove and replace a section of the pavement, any remaining portion ofthe slab adjacent to the ts that is less than 1.5 meters in length should be removed and replaced.
8-19 Curing Immediately after the finishing operations and the concrete has sufficiently set, the entire surface of the newly placed con-
crete is cured in accordance with either one of the following methods:
1. 2. 3. 4. 5.
The use of cotton or burlap mats. The use of waterproof paper.
Straw curing.
By impervious membrane method. By use of white polyethylene sheet.
Cotton or Burlap Mats. The pavement surface is entirely covered with mats thoroughly saturated with water. The mat is
The pavement surface is tested with a 3-meter straight
placed and weighed to remain in intimate with the pavement and maintained fully wet in its position for 72 hours
edge or other specified device. Areas showing high spots
unless otherwise specifi ed.
291
Elements of Roads and Highways
Concrete Pavement
Waterproof Paper. The top and sides of the pavement is covered entirely with waterproof paper. The units are lapped at least 45 centimeters placed and weighed dorvn to remain in intimate with the surface cover. ts are securely sewed or cemented together not to open up or separate during the curing period. The cover should be maintained in place for 72 hours after the concrete has been placed. The surface of the pavement is thoroughly wetted prior to the placing of the paper.
The units are lapped to at least 45 centimeters placing the sheet rveighed down to remain in with the surfbce covered. The slieeting shouid extend beyond the edges ofthe slab at least
Straw Curing. When straw is used for curing, the pave* ment rs cured initially with burlap or cotton mats until after the final set of concrete or in any case 12 hours after placing the concrete. As soon as the mat is removed the surface and the sioes of the pavement is thoroughly wetted and covered with al least 20 cm. straw or hay measured after saturation of water to last for 72 hours. Impervious Membrane Method - The entire surface of the pavement is sprayed uniformly with white-pigmented curing compound, immediately after the finishing of the surface and before the setting of concrete has taken place. The curing compound is not applied during rainy days. The spraying equipment is equipped with a wind guard and the time and of use, the compound is thoroughly mixed with the pigment uniformly dis-
twice the thickness of the pavement. The covering sirould be maintained in place for 72 hours after the concrete has been placed.
8-20 Rernoval of Forms Fonns for concrete pavement should remain in place undisturbed within 24 hours after pouring. The removal could be done as follows:
l. 2. 3.
Crorvbars are used in removing fonns, pulling out nails and pins but care should be exercised not to break the pavement edges. In case a portion of thc concrete slab is spelled off. it should be repaired irrunediately ivith fresh mortar mix-
ture of 1.2.
Major honevcombed area ilill be considered as defective rvork, to be removed and replaced.
Protectiorr of pavernent
persed throughout the vehicle.
During the Application, the compound is stirred continuously by an effective, mechanical means. Hand spraying of odd widths or shapes and concrete surface exposed by the removal of forns will be permitted.
'lhe curing compound
should have that property to harden within 30 minutes after application Should the film be damaged from €ury cause within 72 hours curing period, the damaged portion shall be repaired immediately with additional compound.
White Polyethylene Sheet. The top surface and sides of the pavement is entirely covered with white polyethylene sheet.
292
Concrete pavement and its appurtenances should be protected against public traffic. and traffic caused b), the workers Protection of the pavement includes the posting of watchmen to direct traffic and the posting and maintenance of warning signs. lights, pavement bridges or crossovers, etc. Anv damage to the pavement prior to the final acceptance of the rvork shall be repaired or replaced depending upon the extent ofthe damaged.
8-21 Concreting by the Stip-Form Method
lf
the contract calls for the construction of concrete pave-
nrent r,vithout r"rsing a fixed fbrm. the follon'ing shall applv
.l9
r
Elements of Roads and HighwaYs
Concrete Pavement
The grade. After the grade or base have been placed and compacted to the required density, the areas to the paving machine is cut to proper elevation by means of properly desrgn machine. The base on where the paventent is to be con-
starting of the paver held to minimum. If for any reason, it is to stop the forward movement of the paver machinethe vibratory and tamping elements are also put to stop immediately. No tractive force is applied to the machine, ex-ept those that are also controlled from the machine.
structed is brought-up to proper profile.
If tl-re density of the base is disturbed by the grading operation, it should be corrected by additional compaction before the pouring of concrete. The grade or base should be prepared suf'hci"ntiy advance of the concrete pouring. If any traffic is allowed io ,rr. the prepared grade, it should be checked and corrected immediately before the placing of concrete'
Placing of concrete. Concrete is deposited inside the form using an approved Slip-Form Paver designed to spread, consolidatc. screed and float finish the freshly placed concrete ln one complete p;lss of the machine. in such a manner that niinimum hand finish is obtained, yet provide a dense and homogeneous pavement in conformity with the specifications'
necessary
Protection Against Rain
To protect the concrete pavement against rain, the contrac_ tor is required to have available at all times materials for protection consisting of standard metal forms or plunks having nominal thickness of not less than 50 mm and a nominal width of nor less than the thickness of the pavement at its edge for the protection of the pavement edges and covering miterial ,,r"h *. burlap or cotton mats, curing paper or plastii sheeting materials for the protection r:f the pavement in case of rain. Acceptance of Concrete
The machine vibrates the concrete fuIl width and depth of the strip being placed. Vibration is accompanied by a vibrating tubes or arms working in the concrete or with vibrating screed or pan operating on the surface ofthe concrete'
The strength level of concrete will be considered satisfactory if the average of all sets of 3 consecutive strength test re_ sults equal or exceed the specified strength fc and no individual strength test result is deficient by more thm l5o/o of the
The sliding forms are rigidly held together laterally to prevent it from spreading. The forms are trailing behind the paver for a distance that no appreciable slumping of the concrete will occur and that necessary final finishing can be accomplished while the concrete is still within the forms Any edge slump of the pavement exclusive of edge rounding in excess of 6 mm is
Concrete which does not satisfy the above criteria, may be rejected unless the contractor could provide evidence, by mlans of a core tests thai the quality of concrete represented by the failed test result is acceptable in place.
corrected before the concrete hardens.
The concrete is held at a uniform consistency, having a slunrp not more than 40 mm. The Slip F-orm I'aver is operated nearly as possible to a c.ontinuous forward movement with all operations from mixing, delivering and spreading concrets are rrlell coordinated to provide uniform progress wrth stopping and
specified
fc.
At least 3 representative
cores are taken from each member of concrete area in place that is considered deficient. core locations should be determined by the supervising engineer so that. there rvill be least impain,ent of the strength of itructure. The obtaining and testing of drilled cores shall be in accordance witlr AASHTO T -24 requirements. Concrete in thr: area represented bv the core rvill be consi_
Concrete Pavement
Elements of Roads and Highways dered adequate
least 85olo
of
ifthe
fc
normal lot length, lot.
average strength of'the cores is equal to at
and
if no sinsle core is less than '15o/o of the
specified strength.
4. Other areas like
it
shoulo be included in the previous
intersections, entrances, crossovers,
will be grouped together to form a lot. Each lot will be divided into 5 equal segments and one core will be obtained from each segment in accordance with ramps> etc.,
If the strengih of controlled specimen does not meet the requirements, and it is not feasible or not advisable to obtain cores from the structure due to structural considerations, payment of the concrete will be made at an adjusted price due to strength deficiency of concrete specimen as specified.
AASHTO T-24 reouirements. Pavement Thickness
It is the intent of this specifications to set pavement into Deficiency Strength of Concrete Specimens in percent
Percent of Contract
Price allowed
Less than 5 5 to less than 10
l0 to less than
ln calculating the average thicliness of the pavement. individual measurement in excess of the specified thickness by more than 5 mm, and measurements less than the specified thickness by more than 25 mm, should not be included in tire average thickness.
100
15
15 to less than 20
20 to less than25 2,5 or more
80 70 60 50 0
When the average thickness of the lot is deficient, the contract unit price will be adjusted to the thickness in accordance with the paragraph below re Adjustment for thiclmess.
8-22 Talerance and Pavement Thickness
Individual area within the segnrcnt found to be deficient in thickness by rnore than 25 mm rvill be evaluated by the supervising engineer, and if in his judgment the deficient areas warrant removal, it must be removed and replaced
Thickness of the pavement will be determined by measuring the core from the completed pavement in accordance with AASHTO T-l 48 requirements.
i.
a
uniform thickness as planned for the average of each lot as defined.
by the contractor at his expense.
The cornpleted pavement will be accepted on a lot basis. A lot is considered 1000 linear meters of pavement slab rvhen a single traffrc lane is poured or 500 linear meters rvhen two lanes are poured concurrently.
2.
The last unit in each slab constitute a lot in itself when its length is at least I .2 of the nominal lot length.
3.
tf the lerrgth of the last unit rs shorter than
112 of the
nor-
4.
When the measurement of an\. core is less than the specified thickness bv more than 25 mm, the actual thickness for pavement in the area u,ill be determined by taking additional cores at no less than 5 meters interval parallel to the centerline in such direction from the affected location until a core is found in each direction which is not deficient in thickness bv tnore than 25 mm.
2el 2()(\
Elements of Roads and Highways
Adjustment for Thickness
CHAPTER
When the average thickness of a pavement per cient, payment for the lot will be adjusted as follows: Deficiency in the average thickness
lot is defi-
price lot
per lot (mm) 0-5
ROAD MAINTENANCE
Percent ofcontract
i00% paynnent
6-10 I t-15
95 85
t6-20 2t-25 More than 25
70 50 Remove and replace
9-l
Highway Maintenance
Highway mainte,lrance begins just after the construction, ,""onttrortion or rehabilitation of the roadway facilities. As defined by AASHTO; "Maintenance is the preservation 1n-d keeping if each type of roadway, roadside, structures and faciifie; a; nearly as possible in its original condition as con' structed or as subsequently improved the operation of highway safe transporfacilities and services to provide satisfactory and tation."
Methods of Measurement The area to be paid under this item is the area in square meter of the concrete pavement placed and accepted in the completed pavement. The length is measured horizontally along the centerline of each roadway or ramp. Curb and gutter will be included in the area of concrete pavement measured. Opening to Traffic The project engineer will decide when the pavement may be to traffic. The road will not be opened to traffic until after test specimens molded and cured in accordance with AASHTO T-23 have attained the minimum strength requirements. If such tests are not conducted prior to the specified age of the concrete, the pavement will not be opened to traffic until after 14 days from the time concrete was placed. Before opening to traffic, the pavement should be cleaned and ts completely sealed. opened
798
Objectives of Highway Maintenance
1.
2. 3.
Highway programs and activities are measured by the amount of expenditures for construction of new facilities and reconstruction of existing structure with the aim of keeprng up withthe traffic demand. Maintenance has its own role: by giving priority to local, rural and urban facilities particularly the paving and rehabilitation after the construction has been completed' Maintenance is focused on the do betterment proiects' It includes grading and paving for short alignment changes, to correct steep grades or sharp curves, re-surfacing and mulching, planting, flood and erosion control'
Relationship
1.
b
etw een D esign, C on stru
ction and Maintenan ce
Poor preparation of the base, insufficient slab thickness and poor mixture ratio will only result to the very expensive road repair. lndeed, management absorbed the end result of design and construction inefEciency' 299
1'l
/
Elements of Roads and Highways
2. 3. 4. 5.
Road Maintenance
Poor drainage design will mean ernsion or deposition of materials that requires costly clean up operations. Sharp ditches and steep slopes require costly manual labor maintenance as compared to flat ditches and slopes that allow equipment to work at a lower cost. Narrow road lanes usually forced large and heavy vehicles to travel with one set of wheels near the edge or off the pavement, giving the maintenance personnel serious problems in the care of pavement edges and the shoulder. High maintenance cost is the result of poor design or construction methods. This is the main problem that causes numerous demolitions and unending reconstruction ac_ tivities being undertaken by the highway people.
pen'tiic and irnmediate correclion of involves making the facilities as near the newly constructed or reconstrusted conditions as possible. The utilization of manpower is what makes the mainte'ance very costly. cost could be reduced substantially, if rnaintenance operations are done by the use of equipment. Unforfunately, rnstead of using modem equipment as a product of modern technology, Highway Managernent retum to the use of primi_ tive tools the like of traditional pick, shovels, hoe, sclthe, axe Maintenance calls for
unlbvorable conditions.
It
2. 3. 4.
Shoulder and approach maintenance Bridge mai.rtenance
Traffic services.
Road Surface Maintenance Unlike construction involving high volume of work, maintenance operation, deals with small amount of work at separate
locations. Road maintenance requires speed performance to cause the least possible disruption and danger to traffic. Maintenance operations requires:
1. 2. 3. 4.
For Gravel Roads, blading and periodic re-shaping or resurfacing is a routine periodic maintenance activity.
Ror Surface Treotment of low q/pe bituminous pavement, maintenance could be patching, seal coating, remixing and relayrng.
For Slick Asphalt Surface, roughening, burmng or nonskid seal is required. For Concrete Road, maintenance could be removal and replacement or filling of damaged areas. Sometimes t sealing or mud-jacking or under-sealing is relatively common maintenance work.
or machete. One particular example is the Community Employment Development Program (CEDP) with main objective girrlrrg e*-
ployment
to the people of the rural
"f amount areas. Large
of
money were spent for the purchase of traditional primitive tools and for manpower payroll disbursing seve'al miliions for nothing except for political gimmicks.
The projects were summarily sacrificed when 50% of the appropriation was spent for labor payroll without accomplishment.
Maintenance is Categorized into:
l.
Road Surface maintenance
Maintenance of Shoulder and Approach Maintenance of the shoulder and approaches of the highway is governed by the surface characteristics in the area.
1. 2. 3. 4.
Sod shoulders should be removed and periodically bladed down to the roadway elevation to avoid entrapment of water in the traveled way. Grass prevents shoulder erosion. If necessary, fertilized, re-seeded, or treated to keep them in good conditions. Gravel and earth shoulder should be maintained by blading under favorable weather conditions.
Rutting or setting of the shoulder should be corrected at once by reconstruction or re-surfacing.
300 301
Elements of Roads and Highways
Maintenance of Roadside The type and kind of roadside maintenance depends upon the following conditions
4. 5. 6.
:
l. If
the roadside is full of grass, mowing closer to the shoulder is the answer. If necessary, grass at the roadside be fertilized or treated with lime. ln some areas, re-
7.
seeding may be required.
2. If the roadside 3.
has dry grass considered as fire hazard, burning or plowing is the solution. If bushes cover the back-slope, trimrmng is necessary to
maintain clearance and sight distance. The Ingenious Machine usedfor Roadside Maintenance
concrste.
8.
Correction is to remove the concrete, clean the steel and apply new material such as polymer ccncrete. 9. Sometimes seal-out or overlay of asphalt materials are used as protective covering. 1 0. Check the bridge deck deterioration by:
a
a) Applying waterproof membranes b) Applying latex modified concrete. c) Impregnating the deck with polymers. d) ing electric currentthrough reinforcing
Mechanical sod cutter Cornbined seed and fertilizer spreader. c. Power mowers. d. Portable grass cutter
b. e.
Bushmower
I
f. Bush chopper
2. 3. 4.
Cleaning
of ditches, culvert, drop inlets and catch
to accommodate free flow of water. Removal of sediments, branches and other debris gathered attrash racks, culvert and structure entrances. Repair of eroded channels and dikes. Riprap and bank protection to prevent recrurence.
For steel bridge structure, the routine maintenance calls for cleaning by sandblasting, flame, or other means of re-
2.
painting. Cleaning and re-sealing of deck ts that are extruded or
3.
filled with dirt. Repair of drainage handrails.
302
an epoxy coated reinforcing steel
Traflic Service basins
Bridge Maintenance
l.
l. If decks are dismantled,
steel.
may be used.
Drainage Maintenance
l.
Re-surfacing of rough or slicky deck surface. Correct serious scour around the pier and abutments. Most bridges maintenance is considered specialized work. Traveling crews exclusively for bridges work alone is a function of the maintenance operations. Concrete bridge decks normally deteriorate due to deicing salts. The problem starts when the salt penetrates and corrodes the reinforcing steel that spall-off the overlaying
Maintenance operations of highway includes the traffic services like:
l. Stripping is a continuing functions 2. J. 4.
Repair of road signs. Maintenance of strest and highway light and signals. (sometime the functions of the local government) Coping up with emergencies. Personnel on patrol to keep the road open, and rescue stranded vehicles.
9-2 Maintenance Management Before, maintenance is regarded as secondary functions
of
the Highway agency. The personnel of the maintenance sections J tr--t
Road Maintenance
Elements of Roads and Highways
often felt that they are regarded as secondary class employees of the Highway agency. Indeed, the spoil system exist wherein the maintenance positions are used to pay political favors or buy patronage . Today, maintenance and its management are considered the most intricate and ever changing highway technology. Maintenance is now regarded as one of the most important part of the Highway agency considering the appropriations and expenditures involved for maintenance program. Continuous studies have been going on focused on the best mariagement, time utilization, productirity, methods and man-
2.
Two mowers working side by side accomplish less than when they work separately. Conversation time eats most of the working time.
3.
Not less thzur one and one half of two hours a day is spent unproductively for the preparatory operation and travel of the mower to the job site.
There is no specific number of mowing the road shoulder per year but normally, from one to four times depending upon the physical condition of the shoulder. Grass by nature grows faster during rainy days than on summer time.
agement on maintenance.
Studies showed ttre need for improvement on the following field.
l.
Education
2.
More detailed and careful plarming and scheduling of work and establishing standards for the level of mainte-
in management technique for
7.
Major improvernent of maintenance tools and equipment Providing a better and efficient communications. Establishing lines of authority and responsibilities. For the maintenance orgaruzation to succeed, staffrng with permanent trained and dedicated personnel is the solution.
Effective management system requires efficient, accurate and fair budgeting and reporting procedures. But how to implernent these, is next to impossible, because it is difficult to overcome varied istration, and behavioral
problems. One example is the studies made on roadside morving which shows that:
1.
The use of better equipment could accomplish mowing from 3 to 6 times as much area compared to the use of poor and antiquated tools.
:r04
l.
maintenance engrneers and foreman including its field personnel.
nance.
3. 4. 5. 6.
Requirements for Maintenance Management
2. 3. 4.
To stabilize the standard level of maintenance by setting performance standards for workers crew and maintenance units" This requires Methods Time Measurement (MTM) expected output for particular operations that are predetermined.
To develop an accurate monitoring and fair reportrng system and to compare actual work with the expected production. To develop a management system that will give efficient work scheduling assignment. To develop effective procedures, methods and machinery or organization to carry out individual maintena:rce operations.
Effective maintenance management could be achieved by gaining the enthusiastic of the personnel by educating them with the new methods plus acknowledgment of their efforts through personal recognition and by financial reward for there is a saying that we cannot live by love alone.
The roadway to the development in maintenanr:e is still far. While others have already gonefar advanced, v'e are just about to begin.
i05
Elements of Roads and Highways
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9-3 Rehabilitation
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during bad weather, heavy rain, removal of fallen trees, flood, erosion etc. Maintenance personnel are exposed to accidents, hazards during their maintenance or rehabilitation work.
On some instances, Highway agency is legally held responsible for injury to person or damages to property resulted from poor highway maintenance. Unfortunately, employees and supervisors are even charged in court, condemned and crucified by the media people prior the hearing of the case.
.E
-
Personnel who are devoted to the maintenance work are not those who just kill the time and collect their salaries. Personnel responsibility for keeping the roadrvay open to traffic moving under all conditions. Personnel rescue operation in assisting stranded motorists
Maintenance personnel deserves to be recognized and rewarded accordingly, unfortunately, these dedicated people are sometimes victims of neglect especially in the promotion and increase ofsalaries.
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Effective maintenance personnel activities are rneasured under the following criteria.
T
{s * €
Pavement rehabilitation is an activity primarily to provide good riding and skid resistance or to improve the structural effectiveness of the pavement. The FIIWA defined rehabilitation as:
" Resurfocing, restoration and rehabilitation work, restoring to the original tofn usable condition without addition to the original capacity. " According to AASHTO, the primary objectives of pavement rehabilitations are:
L 2. 3. 4. 5.
To To To To To
Elements of Roads and Highways
Road Maintenance
improve the smoothness of the road surface. extend the pavement life. improve the skid resistance of the road. construct the sections with poor foundations. improve the drainage facilities.
Reconstruction refers tp the removal of existing pavement and replacing them with a new pavement and under course.
The efficiency of the highrvay system could be rated by:
l. 2 3 4. -5
existing materials
of energy requirements.
Maintenance report. Public comments and suggestions.
Pavement Recycling is Categorize into:
l. 2. 3.
Restoration and Rehabilitation Restoration and rehabilitation work includes
:
Replacement of defective ts. Repair of spalled ts. Substantial pavement work. Reworking or strengthening of sub-base.
Recycling existing materials to improve their structural inlcgrity. Adding under drains. lmproving shoulders Removing and replacing deteriorated materials.
Pavement Maintenance refers to actions that are corrective or preventive.
i08
of
working on asphalt rnaterials, portland cement or lime.
Skrd tests.
Resurfacing is the addition of pavement layer over the existrng roadway or bridge deck surface to provide additional capacity. The additional re-surface pavement should not be less than 20 mm in thickness.
6. 7. 8.
Recycling means the repeated use
Generally, recycling contribute to the stabilization of cost conservation due to inadequate material resources and reduction
Sufficiency ratings. Accident data.
Resurfacing
l. 2. 3. 4. 5.
Overlays could be either by Portland cement or Asphalt concrete laid on arr existing pavement.
The trpe of matcnals to be used. The prooedure to be employed. The structural benefit to be gained.
The Recycling Procedures could be as follows
1. Surface Recycling consists of reworking about the top surface of asphalt pavement. It is applied for the treatment of ravelling, u'heel truck rutting, flushing and corrugations. The work includes the use of heater-planer, heater-scarifier, cold planers and cold milling. The disadvantages of their use are the presence ofnoise, heat and air pollution.
2. In place Surface and Base Recycling. This procedure involves pulverizing all existing pavement, followed by reshaping and compacting. Before relaying, the materials are upgraded with lime, portland cement or chemicals. This method is used for both asphalt and portland cement concrete pavement. One advantage of this method is the ability to increase the load carrvlng capacrty of the pavement without major changes in the grade.
3.
Central Plant Recycling is the removal of materials from the roadway, crushing them, mixing in the plant then laid and compacted with conventional equipnrent. 3u9
Road Maintenance
Elements of Roads and Highways
Both asphalt and Portland cement concrete are reprocessed to make aggregate materials for stabilization of the base course. The recycled materials when used as base courss is blended with additives lrithout heat such as Portland cement, Lime or Cutback or Emulsified asphalt. For surfacing, it is heated and then blended with new asphalt cement or recycling agents and sometimes with new aggregates. Advantages and Disadvantages of Recycling Categories
A. Surface Recycling Advantages:
L 2.
It reduces reflection cracking. Promotes bond between the old pavement and the thrn
B.
In-Place Recycling
Advantages: l. Significant structural improvements. 2" Treats all types and degrees of pavement distress. 3. Reflection cracking can be eliminated. 4. Frost susceptibility may be improved. 5. Improved riding quahty. Disadvantages: 1. Quality control not as good as from the central plant. 2. Traffic disruption. 3. Pulverizing equipment repair requirement. 4. Higher in cost.
C. Central Plant Recycling
overlay.
Provides transition between the new overlay and the existing gutter, bridge, pavement, etc., that is resistant to raveling (eliminates feathering). 4. 5.
6. 7.
Reduces localized roughness. Treats variety of types of pavement distress such as raveling, flushing, corrugations, rutting, oxidizing pavement faulting at a reasonable cost. Improved skid resistance. Minimum disruption to traffic.
Disadvantages
L 2. 3. 4. 5. 6.
Limited structural improvement. The heater-scarifuer and heater planing has limited effectiveness on rough pavement without multiple es of equipment.
Limited repair of severely flushed or unstable pavements. Some air qualrty problems. Vegetation closer to roadway may be damaged. Mixture with maximum size aggregate greater than I inch cannot be treated with some equipment.
310
Advantages:
l. 2. 3. 4. 5. 6. 7. 8.
Significant structural improvement. Good quality control Treats all types and degree of pavement distress. Reflection cracking can be eliminated. Improved skid resistance. Geometrics can be more easily altered. Better control if additional binder ar aggregate is used. Improved riding quality
Disadvantages:
l. 2.
traffic disruption May have air quality problems at plant site. Increased
Maintenance and Rehabilitation programs are based on different types ofcollected data that includes:
1. 2. 3. 4.
Surface Surface Surface Surface
roughness distress
deflection
friction or skid resistance
3ll
Road Maintenance
Elements of Roads and Highways
9-4
Definition of Surface Roughness is defined as the irregularities in the pavernent surfbce that adversely affect the riding qualrty
Surface Distress is defined as any indication of unfavorable pavement performance or signs of impending failure, or any unsatisfactory performance is a sort of failure.
Any type of distress that may be observed includes any one of thc following:
a.) Fracture
associated with load and non-load cracking.
b.) Distortion is a permanent deformation of faulting. c.) Disintegration
such as spalling, ravelling and other failure
of the pavement.
For each Distress I'ype, the corresponding damage, severity and locations are specified. All data are gathered and indicated in the survey form as a guide.
In cass cf Surface Deflection, measurement of the changes in pavement surface level between the loaded and unloaded segment is the basis for rehabilitation design strategies. TLre design strategy is to determine the structural adequacy or the ability of the pavement to resist traffic load without developing undesirable distress.
Distress observations could be
of static
deflection, steady
state of deflection or by the impact load response as determined by the Dynaflect and Falling Weight Deflection respectively.
Surface Friction is determined from gathered data identi$ing a pavement section having low coefficient of friction. There are equipment available to determine the skid number. It is measured using a locked wheel trailer (ASTM Method E-274) or by the Yaw Mode trailer where the wheels are skewed in accordance n'ith the direction of travel. -l
l,
Bvaluation and Maintenance of Concrete Pavement
Maintenance decisions are based on pavement condition data gathered from project to project basis. From these gathered
data, it is determined which project calls for maintenance or rehabilitation including the decisions required to correct pavement deficiencies. Decisions however, are made on a yearly basis.
Considering the increasing length of the roadways, the management on the basis of field observations alone is becoming difficult hence the objective method of evaluation was introduced:
L 2. 3.
Those projects that need immediate maintenance or rehabilitations are listed on the priority projects. .The type and kind of maintenance or rehabilitation required is specifred. What strategy of maintenance or rehabilitation would be adopted now and in the future to minimize life cycle costs or maxirnized the net benefits.
Maintenance of Concrete Pavement As mentioned earlier, maintenance of the roadway of any type is a routine activity. Maintenance of good concrete road could be arsued as follows:
t.
Sealing cracks of transverse and longitudinal construction and expansion ts is one recommendation where maintenance Engineers could not agree on one question whether sealing the narrow cracks is effective or not. The practice however, is to clean properly wide cracks or spalled ts then applied with sealing materials to prevent the intrusion of extraneous material. and to block the downward penetration of surface water.
3t3
Elements of Roads and Highways
For small and scattered broken surface on good concrete pavement, patching with concrete is economical. On affected portion old concrete is removed by vertical straight line cut parallel and perpendicular to the roadway centerline. For corner repair, the angle from the roadway center3.
4.
5.
6.
line should be greater than 30o but less than 60'. Sections that are removed should have a minimum area of 20 square meters. If the sub-grade appears to be weak, and doubtful to carry heavy axial load, replace it with suitable materials and compact properly. The new concrete slab should be as thick as the original pavement. Good practice demand that extra trrickness ading the old concrete be provided extending the patch under the old pavement to width and depth of l0 centimeters. Additional cement is necessary 1o produce high early strength concrete or an accelerator such as calcium chlorrde is used for patching if early use of the pavement is desired. The ideal time to make repair of concrete pavement road is in the evening. Pavement surface with spall from freezing and thawing or salt action are levelled with asphalt mixture or surface
treatment. Another method is to patch with concrete bonded to the old concrete with a cement-water or epoxy. 7. Spalled t can be repaired with cement grout containing epoxy mixed with catalyst.
Mud Jacking Mud Jacking is a maintenance method adopted to restore the sub-grade under pumping pavement and to level uneven slabs. The liquid filler is injected under the slab through drilled holes. The mud or slurry, filled all the voids that if continuously injected applying hydraulic pressure will force the slab upward. Slurry for mud jacking consists of a mixture of fine grain aggtegate, portland cement and water or iul addition of small amount of asphalt. A mixture of one part cement, and three to four parts of ground limestone, could be used as slurry for mud jacking. 314
Road Maintenance The mixture must through the pump without gumming. It must flow readily under the pavement to the smallest voids. The mixture must harden rapidly wrthout excessive shrinkage and not becoming hard and brittle. Take note that the spacing of the holes through the concrete should be planned carefully when the slab is to be lifted by pumping slurry into several holes. Frequent movement of the nozzle is necessary so that the lifting will be in small increment.
Under-Sealing Under-sealing is an alternative for mud jacking. Heated asphalt sometimes is used. The advantage of under sealing is the formation of asphalt as seal against the penetration of surf,ace water into the sub-grade.
9-5 Highway and its Environment Early roads were patterned after the railroad of the same period. The principle behind the construction of early road is to construct the cheapest roadrvay that would serve traffic under all conditions of weather without regards to its environment. Roadside development was not included in the program. Shoulders and right of way are narrow or non-existing at all. Side slopes were too steep; drainage and ditches, channels and structures were designed to protect the roadbed without regard to erosion outside the roadway limit. These crude practices in road building have brought unsightly conditions and high maintenance cost until such time that design standards were gradually modified and improved. The later development and improvement of roadway has incorporated the following features:
l.
Pleasing views and surroundings were developed sacrificing a little costs or distances to enhance driving pleasure. 315
Elements of Roads and Highways 7.
Long sweeping horizontal curves are acceptable than
3.
short curve connected by long tangents. Choppy or broken back grade line were not only flattened
but smoothened. In rough areas, the depth of cuts and filI heights were lowered to reduce scare and slope erosion to a minimum
5. 6. 7.
level.
Retaining walls are sometimes helpful and improve the attractiveness of the roadway. Modern highway now provides wide roadbeds, shallow wide gutter and ditches, flat back slope and cuts, and flat side slope on
fill.
Top ofthe cut banks and toes offills are rounded to blend rvith the original ground.
These features of the roadway give safer roadbed and a pleasing approach. Erosion occurs more slowly or prevented on flafter slopes. The result is less expense for cleaning gutters and ditches. Mowing could be done using power equiprnent that substantially reduces maintenance costs.
Wider right of way has become a necessity in roadside development for the following reasons:
l. It allows blending of the road into the natural landscape. Z. [t provides space to plant screening in front of unsightly 3.
and objectionable areas and other undesirable objects. It isolated the highway visually from its surroundings and freeing the roadside ofhazards.
Roadside is the entire right of way except the travelled way. planning roadside development, planners were conscious of In the cost maintenance including the cost of morving, trimming and cleaning. Roadside development is sometimes referred to as roadside beautification made after the road construction is completed. Roadside development without question provides a more pleasing environment for travelers, less maintenance cost and
3i6
Road Maintenance safer highways. The roadside development is under the care of the Highway agency, although there re adjacent propert-v homeowners who sometimes contribute to the beautification of their surroundings including the roadside itself for aesthetic consideration that they themselves enjoyed.
9-6 High\ryay Beautification Highway beautification is a broad term that includes activities like:
l. 2. 3.
Landscaping and roadside development within the rights of way. Improvement of strips and land adjacent to the highway for restoration, preservation and enhancement of natural beauty.
Acquisition and development of publicly owned and controlled rest area- recreation areas and sanitary areas including other facilities.
Factors that Contribute to Beautification
1. 2. 3. 4.
Good location Good design
Construction Maintenance
Outdoor Advertising The control and removal of outdoor advertising had long been controversial in the beautification of highways. A court ruling on these aspects states that: "The concept of public welfure, for the purpose of which the legislative may exercise police power, is broad and exclusive, and the value it represents is spiritual and aesthetic as well os physical and monetary. " 317
Elements of Roads and Highways
For public interest, the government should extend full assistance to the control and use of the areas adjacent to the highway by regulating the erection and maintenance of outdoor advertising signs, display or other devices within a reasonable distance from the edge of the right of way but still visible from the nrain traveled way.
Road Maintenance
To maintain balanced distribution of population and use of resources that will give high standard of living and wide sharing of life's amenities. To irnpart that all person has the responsibility to contribute to the preservation and enhancement of the environ-
6.
7.
ment.
9-7 Environmental Laws
9-8 Environmental Effect of Highways
The government had ed enough laws to protect the environment. The Environmental Laws has the following intent:
mental effects oftransportations are as follows:
1.
The govemment recognizes the impact of man's activities in relation to all components of the natural environment more particularly:
a) The influence of population growth b) The high density urbanization c) Industrial expansion d) Resource exploration e) The expandingtechnological advances f) Restoration and maintenance of environmental qualrty to the welfare and development of man.
2. 3.
The present generation must fulfill the responsibility as trustees of the environment for the succeeding generations. To assure all Filipino people of a safe, healthful, productive and aesthetically and culturally pleasing surround-
l.
Air
and noise problem
2. Traffic induced vibration 3. Accidents 4. Armoyance caused by water pollution,
dust and dirt.
Air Pollution Control Air pollution be it from fixed or mobile sources is the main concern in most urban areas. Air pollution is tlre result of progress. It comes from discharges into the air of non-reactive pollutants including carbon monoxide, sulfur dioxide, sulfates, dust smoke and lead. The highway pollution problems are two dimensions. They are:
1.
2.
of
Area wide effects of preliminary reactive pollutants. High concentration of non-reactive pollutants at points or corridors along or near highways.
ings.
4.
To provide the widest beneficial use of the environment without degradation and risk to health or other undesir-
5.
To preserve some important historic, cultural and natural aspect of our natural heritage and whenever possible an environment which uphold diversity and variety of individual choice.
318
The main objections of community complaint on snviron-
able consequences.
Motor vehicles are mainly the contributor to both forms of pollutants estimated at 70%o carbon dioxide, 50% hydrocarbon, and 30%' of nitric oxide. The area condition is acceptably worst when temperature inversions trap pollutants near the ground surface when there is little wind or no wind at all. Concentration becomes extremely high atrecting human life and even some vegetation are killed, stunted or the foliage is bumed. 319
Elements of Roads and Highways
Various approaches to reduce area pollutants were planned and employed including future approaches such as:
l. 2.
7_
By Land Use Control. One example is the limitation and control of industrial-commercial development where their construction and land use would contribute to pollution. To Lower the Emission. This is by lowering the emission of pollutant from existing machineries.
Modiftcation of the fixed existing fociliries such as substituting low sulfur coal to reduce the release of sulfur dioxide.
Lowering pollution coming .from motor vehicles that falls under the following categories:
a)
Reducing the output of pollutants by rnaking them fuel efficient and controlling pollutant output.
b)
Limiting vehicle travei by shifting travelers to
c)
other mode using electric current. Cuttrng fuel consumption and pollutant output by
d)
improving traffrc flow. A set of standard to be met by new vehicles.
Noise Control Noise is defined as unwanted sound. Noise is measured in decibels with a common unit dBA. This single unit combine sound intensities from all frequencies above 100 per second and strongly react in the human ear. Sound at ldBA level could be hardly detected by human ears, but an increase of l0 on the decibel scale means tenfold increase in intensity. In a quite residential area at nighg the ambient noise is measured from 32 to 43 dBA. The urban residen-
Road Maintenanee
In of
conversation
or
communication, these sound
level means that at 65 dBA a conversation is difficult at a distance of i.00 meter and at 75 dBA an ear has to be plugged by a finger in order to hear a telephone conversation.
Transportation noises are complexn studies showed that:
1.
Complaints are focused on interference with speech. TV viewing or sleep related to increase ofsound above anrbient noise level.
2. 3.
Increase up to 9 dBA , complaints would be widespread and there would be community reactions. Highway noises near residences at peak noise of about 70
dBA bring f'ew cornplaints, at 75 dBA, complaints are likely and 80 dBA will invite letter of petition and protest.
9-9 Construction in Relation to Roadside Del'elopment At the time of grading
operations, topsoil should be pre-
for future landscaping. Likewise, trees outside the distance limit from the travelled way, should be protected from damages caused by man and equipment. Removing of soil or fills from along the right of way called side borrow should be avoided, and borrow fills out of sight from the roadway is prefserved
erable.
Objects of interest like rocks, outcrops in cut slope or trees fill should be preserved for pleasant view. Rugged slope in borrow areas and along roadside are dressed to encourage the retum of native plants and shrubs.
at toes of
9-10 Vegetation and the Flighways
tial district at daytime limit is aboul4l to 53 dBA. In industrial areas tlre range is 48 tn 66 dBA, and in downtor,r.n commercial
Ground cover is defined as low growing herbaceous or woody plants more than one meter at maturity. Both low shrubs
areas with heavy traffrc is 62 to 73 dBA.
and vines are included
320
321
Elements of Roads.and Highways Ground cover is an alternative to grass in controlling erosion by wind and water. It also serves as insulation that reduces sloughing caused by freezing and thawing. Mat forming plants are considered best ground cover for protecting slopes and other roadside areas. There are those that root from decumbent branches and those that spread from suckers and shoots.
Other Vegetation Desirable for Roadside Protection
l.
Road Maintenance
3.
4.
Bushy dense foliage plants, and those producing litter
with great water holding capacity are considered
? 3. 4.
good vegetation to protect the roadside against erosion. The rapid growing species with inconspicuous flowers to prevent distraction and vandalism are preferred. Fire resistant plants with the abilrty to sprout after buming are much desirable. The cogon grass is one example. Plants that are subject to disease and insect damage, poisonous or irritating to the skin or that may become agricultural pest should be rejected.
For median strips and islands, erosion control is but one of the functions of ground covers. Properly selected plants prevent headlight glare without affecting distance and provide a contrasting background that also guide traffic directions. Tires and Shrubs Trees and shrubs are effective means of providing interes! variety and beauty to the roadside. Those that are native to the area are more preferred than the imported variety. The following are important tips in planting.
l. 2. 322
For rural roads, the objective is to preserve or recreate a natural foreground in harmony with a distant view. Existing well placed trees should be preserved while ugly and obstructing growth are removed. Replanting should be considered only when irregular in-
5. 6. 7
.
troduction oftrees and shrubs serve to highlight the natural beauty or where it is particular$ desirable to screen unsightly objects. Trees should be planted back a distance from the traveled way to provide recovery area for vehicles that run offthe roadway. A minimum distance of 9.00 meters from the lane edge is recommended (See "A guide for highway landscape and envi ronmental desi gn " ) Row planting along rural road is not considered a good taste. It spoils distant views with a monotonous design. The formal arrangement oftrees and shnrbs is suitable for urban freeways and expressways. Group planting creates an occasional point of interest or call attention to intersections, bridges or other point of hazard. Continuous planting is appropriate to screen unsightly roadside condrtions or to insulate residential areas frorn the road^
Avoid monotony over long stretches of the route. The solution is to group flowering trees and vines at best and appropriate locations.
9-11 Parking and Rest Area Parking turnout to accommodate stopping off the traveled way is an important adjunct to major rural highways. Wayside rest areas are necessary facilities of the highway wherein motorist stops, relaxes and use sanitary facilities. Wayside rest areas should be located on those with natural features that make the area:
1. More attractive. 2. Those that are accessible and safely located. 3. Those with sufficient area and with existing shades. Locations where public use will create fire hazard or otherq.ise affect ading property should be avoided. 323
Elements of Roads and Highways
cHAPrE"ffi
Likewise, location closer to cities and towns are not advisable, because it will just be monopolized by the town people. The site must have adequate driveways and parking space separated from the traveled way with bumper rails or curbs to confine vehicles. and
TRAFFIC ENGINEERING
if possible, provided with fence.
'
Without questions, highway rest areas are worthwhile, but highlvay offrcials and maintenance personnel object to their establishment because motorist s :re untidy and are sometimes vandals making maintenance difficult and very expensive.
-
10-l Road Traffic Signs The importance of road signs have been recognized world wide because of the increasing incidence of road accidents due to ttre volume
oftraffic
and bad habits of motor vehicle drivers.
The United Nations Conference on Road Traffic was held in Vienna, Austria on October 7, to November 8, 1968 under tlre auspices of UNESCO. The participating countries including the Phiiippines agreed on the Road Traffic conference to hdve a
sepilate conveirtion for Road Signs and Stgnals as necessary to facilitate international road traffic and to increase road safety' On June 6,1973, Presidential Decree No. 207 was issued by then President Ferdinand E. Marcos which states and partially quoted:
Wereas, th.e contracting parties to these conventions to which the Philippines is a signatory, have agreed to accept the system of tffic, road signs, signals and symbols and road markings described in said conventions and to'adopt the same as soon as possible.
for the ratif cation internationally, presigns and sigials in the Philippines, specially so, because of the intensifed government campaignfor road safety. Whereas, there is now an urgent needed
of these conventions in order to adopt icribed unifurm rules of traffc and ,oad
Whereas, the urgent need for adopting the unifurm trffic rules, road signs and signals as prescribed in the conventions is made more necessary because of the considerable number of foreigners and tourists that are now operating motor vehicles on Philippine roads.
iz5 3 ZL+
Traffic Engineering
Elements of Roads and Highways
After more than 20 years, although majority of the world countries have already applied the recommendations of the Vienna Convention, some countries like USA and the Philippines have still difficulties in implementing the international traffic system"
T'he three efficacy principles of Unifurmity, Homogeneit)) and Simplicity Ne not being inforced. Instead, a very complicated mixture of lnternational and US rules are adopted which leads to misunderstanding and consequently non-respect of the rules.
Uniformity includes the prohibition to use unofficial signs and markings.
Homogeneity requires that in the same conditions, the notices signs or markrng with the same value, sanrc importance and lcoated according to the same rules. Simplicity is to avoid superabundance of signs that over strain the drivers having the tendency to neglect the given instructions. Sometimes drivers cannot read, understand, or the meaning of the signs or markings.
Road Signs has the Following Objectives
l. 2. 3. 4.
To To To To
lead to a safest road traffic.
facilitate this traffic. indicate or to remind some particular traffic rules. inform the drivers how to use the highway.
The Different Categories of Signaling I)evices are:
l. 2. 3. 4.
Road Road
taffic
signs.
traffic signals.
Pavementmarkings. Guide posts and delineators
Road Signs are Classified into the Following Categories.
l. DangerWaming Signs 2. Intersection Signs 326
3. 4. 5. 6. 7. 8. 9.
Prescription Signs a) Prohibitive b) Obligation General Information Signs Direction Signs Agglomeration Signs Railway Crossing Signs Temporary Signs (on road works) Special Instruction Signs
Visibility and Legibility Signahng devices whether horizontal or vertically installed has the following objectives:
1.
To Inform
2. To Prevent 3. To Guide 4. Act as liaison agents between the driver and the highway alignrnent.
At night, drivers has no complete view of the highway envrronment. His only guide is the headlight. Therefore, road signs and signaling must be effective in the dark. Report of accidents revealed that for the same traffic condition, the percentage of fatalities at night is double than during daytime.
This difference can be explained only by the modification of one factor- Visibility. To be effective, road signs and signaling must be visible and readable considering human eye limit that is not adaptable at night driving
Visibility and Legibility of road signs or the
pavement
markings are dependent on three parameters.
l.
The detection
2. The identification 3. The reading 3Z I
Elements of Roads and Highways
Traffic Engineering
Detection is the minimum area in contrast with the environment perceptibility by human eye.
Valorization Principle means to use only the needed and useful signs. Too many road signs lessen its efficiency. Regula' tory and warning slgns should be installed sparingly because excessive use of these signs will only decrease their authority.
Identification is an analysis of the form and color of the road signs to understand the messages it conveys.
Reading is the fundamental role of road signs conforming alpha numerical language or by the syrnbol of information transmitted to the driver.
to
TABLE
IGI
Typ"
STANDARD FOR.DI AIYD SIZE OF ROAD SIGNS IN CENTIPTETERS
Triangle Side
Circle Diameter
Octagon
Square
Width
Side
Very Big
150
t25
t20
i05
Big Size Normal Sizc
t25
105
100
90
100
85
80
70
Small Size Very Small
70
65
60
50
50
45
40
35
Concentration Principle. Wren it is necessary that some road signs must be seen at the same time, they should be installed for the driver to see at a glance by mght and day. The signs must be set on the same post when the two indications relating to the same point are complementary. For instamce, traffic signal ahead and the pedestrian crossing. This concentration principle however, is limited bythe legibility principle.
Legibility Principle" Excessive efforts of reading or llrolrrory works cannot be requircd from the driver. The indicalions or analogical messages should be reduced, and if necessary, road signs should be properly distributed. Experienced proved that average observer caruiot see and understand at a glance more than two symbols at a time
10-3 The snrall type of road signs are used only when some difficulties prevent implementation of the normal type such as line of trees, mountainous road, reduced shoulders, small side walks and the like. The very small type is used exceptionally in cities for aesthetical considerations.
Warning (Danger) Sign
Warning Sign is used to warn traffic of potentially hazardous conditions on or adjacent to the roadway. Warning Sign is always Triangular in Shape with one Vertical Angle and dark blue symbol, rwo borders one white and red with reflectorized white background.
10-2 Basic Principle of Road Signs The basic principle of road signs is to be perceived clearly by a driver traveling at relatively high speed, whose attention is solicited by the driving requirements. To be useful, road signs must be efficient according to:
l. 2. 3. 328
Valo.rizationPrinciples Concentration Principles
Legibility Principles
There is no exception tq this rule, and the use of yellow color for background is strict$ prohibited for permanent signs. The yellow color is reserved only for temporary signals used during road construction or maintenance work.
Objectives of Warning Signs The objectives of warning sign is to attract driver's attention in the areas where his watchfulness has to increase on of the obstacles or of the dangerous points linked to: 329
Elements of Roads and Highways
Traffic Engineering
AAAA AAAA AAAA AAAA Merging
Tralic
Pedestrian
Hanging
Crossing Animal
Steep downward
road
Approaching
Steep
Two way
Bridge lpproaching Trafiic tight
crossing
upward
road
Nanowing
Slippery
Road under repair
road
road
Rough road
River ahead
Caution ialling stone Railroad crossing
1.
2. 3. 4. 5.
The highway structure such as curves, humps, dips and narowing. Conditions of the road such as slippery, falling rocks and the like. Other transport infrastructure like opening bridge, airport vicinity, railway crossing etc. The condition of vehicles and pedestrian traffic, pedestrian crossing, children area, two-lane highway after a multi-lane highway. Local circumstances such as: factory exit, quarry exit etc.
When
it is necessary to point out a potential risk,
an ad-
vanced danger warning sign is installed. The purpose is to inform the driver that he is approaching the obstacle, the dangerous point or the beginning of a dangerous zone. Road signs pointing to danger zone or intersections should indicate the let gth repeated after each intersection.
Fixed Message Signs Includes:
1.
2. 3.
Detailed direction to motorist of the freeways and warning signs regarding destination and lane occupancy. Signs to notifu motorists of the changes in directions. For low volume rural roads, only directional and kilometric signs installed at intersections and also signs for dangerous condilions.
Road signs should not carry commercial ment other than for traffic control only. There are situations where almost no signs are installed because they are being vandalized or taken away as building materials.
Installation of RegulatorT and Warning Signs Regulatory and Warning signs are installed sparingly bewill only decrease their aurhonty. cause excessive use of these signs
FIGURE 10.1 WARNING (DANGER) SIGN
330
331
Elements of Roads and Highways
LJ\ AA A^\A Dangerous Curve
Dangerous Left Curve
Dangeroue Right
Curve
Dangerou!double curve at lefi
AA
AA Dangerour right
double curve at
Waming Croas Road
Entering Crosa Roao
AA
AA Curve to
right
Curye
A A
Entering Major Crosg Road
A A'
to
lefi
Airport vicinity
Nanowed road
Traflic Engineering For oversized signs on expressway and freeways, white letter on green background with white border is recommeNrded.
Large sizes of signs are effective on expressway or where speed, hazard, accident orperie,nce or competition from lights or other signs is extreme. 3. Excessive use oflarge signs should be avoided because it makes the regular sizes less effective. 4. Non-refleclorized signs are satisfac0ory for most school zone markings, parking conaol, me,n working and other temporary warnirgs that are effective only in daytime or illuminated by street lighting. 5. The Traffic Manual suggest that two signs, one black on white, unreflec0orized and other white on black reflector' ized be mounted on the same standard where speed limits differ between day and night. 6. Signs with significance at night should be illuminated or
2,
7.
reflectorized. The sign message must be simple. The driver in so short a tinne available looking at slgn messages ciumot observe and assimilate large amount of information printed on it.
8. An expressway or freeways usually have two messages and no more than three regarding directions or destination should appear on a single signboard.
FtcuRE 1G2 WARNTNG (DANGER) StcN
Other important Place Information should be given on separate signs. At turnoffs from limited acc€ss facilities, directional sign may be used either:
l. 2.
To indicate the immediate
numzuver wit"\out dstail to
subsequent one or
To diagramthose later movemeds on earlier signs.
Effectiveness of Road Signs
R:50FIGURE
'G3 732
DETAIL OF WARNING (DANGER) SIGN
As mentioned earlier, too many signs will make all of the'rn less effective. I".arge signs overwhehn any smaller ones. Thus, signs often fail to accomplish its main purpose. For example: 333
Tra{Iic Engineering
Elements of Roads and Highways
l. Stop sign to control 2.
3.
4.
vehicle speed in residential areas are useless for being ineffective. Majority of the motorists make a roll stop and few otlers only ignore the signs. Signs like "Slow Children at PIay" have no effect on speeds. Selection of sign message is important because drivers react to them differentlv. The "Slippery When Wet" warning sign is not threatening, but effective only when accompanied by flashers. tf signs convey incorrect information such as safe speed indicator on curve warning sign suggest a speed slower
than the driver find easy and comfortable, they
will ig-
nore subsequent messages, ttrinking that the signs are
5.
only fooling them. If signs tell them tJrat there is ongoing construction or maintenance work ahead when none is actually in progress, drivers will ignore all such signs.
l0-4 Intersection Signs
right of way against the vehicle coming from the right or from the left, except as ottrerwise provided.
Priority Road: Sign 12-9 punctual warning sign of the intersections where the driver has priority against all vehicles. The thickness of the principal road is bigger to avoid confusion with another sign. Sign STOP or GIVE WAY has to be located on the other road.
s@ 3. Non-Priority
Priority Sign Pr and Pz is to inform the driver that he is driving on a priority road or street and that he has the right of waY.
Road
The driver of any vehicle entering a highway from private road shall yield the right of way to all vehicles approaching, entering or in the intersection.
III
Article of the Nght of Way and Signals of the Traffic Code is not clear. Therefore, it is necessary to define the right of way rules at the junctions and intersections. The right of way can be reduced to three possible situations:
1. General Rule.
General Rule, right priority sign W 2-1 warning sign of the intersections where the driver has to give way to the vehicles approaching or entering the intersection on the right.
2. Priority Road
734
necessary for safetY.
Sign R1-1
When the vehicles approaches an intersection from different roads, the driver on the left should yreld the right of way to the vehicle on tlre right except as otherwise hereinafter provided.
Any vehicle
@
The Stop sign is used to ensure caution before entering an intersection. A full stop is
mning onthis type of road has always
The
Rl-l
V Signs Rl
the
Sign cannot be used alone'
It is announce by Rl-
2a sign installed before the intersections like a warning sign. The GIVE WAY sign notifies the obligation of the driver to give way to all vehicles coming from right and left without the obligation to stop. The use of this sign supposes that the sight triangles are effectively implemented and maintained. lt also supposes. that the GIVE WAY sign is announce by R1-2b sign located before the intersection like a warning sign.
335
Elements of Roads and Highways
Traflic Engineering
The Philippine road signs manual (Revised Edition 1982) proposes no less than 22 traffic sign combinations for junctions and intersections. [t is too much number giving the drivers more confusion. The proposal is to use only six types of intersection signs for simplicity.
When signs are located more than 200 meters from an intersection, it should be repeated at half distance, and the two signs should be equipped with distance slgn.
Road signs located betwesn 100 meters and 200 meters be-
Exception to the Right of Way Rules
l. 2.
3.
Vehicle drivers entering a highway from private road must yield the right of way to all vehicles approaching on such highway.
Driver of vehicle upon a highway of any category must yield the right of way to police or fire deparfrnent vehicles and ambulances operating on official business and the driver thereof sounding audible signal of their approaches.
The indicatrons of traffic signals or the orders of a traffic office1 prevails against the right of way rules.
In an intersection where some flows of traffic can be in conflict, it is suggested that the drivers must be:
1.
Notified in time of the existe,nce of intersection.
2. Informed ofthe applicable rigtrt of way rules. 3. Able to see the vehicles approaching upon the other roads.
The first two prescriptions will be implemented by means road signs the third is by sight triangles.
fore an intersection do not have distance sign. Where the distance is shorter than 100 msters or greater than 200 msters it should be indicated on the distance sign' The distance is rounded to the ncarest 50 meters if it is greater than 200 meters. Between 50 and 100 meters it is rounCeci to 50 or 100. The road signs Rl-2a and R1-2b are always located with a distance sign. The distance is rounded to nearest 50 meters if it is grcater than 100 meters" Bstween 50 and 100 meters it is rounded to 50, ?5 and 100 meters. The distance signs are 1ocated under the road signs.
The roadside srgn should be mounted clear of roadside vegetation and clearly visibte under low headlight illuminatron The heigh of the sign base is 1.00 meter above the by "ight. nearest edge of the travel way but this height could be modified to improve visibility. On the intersection island, the signs can be installed less than 1.00 meter to prcvent them from masking the visibilrty.
of
Location of the Intersection Signs On Rural Areas, the normal distance between the intersections and the waming signs is 150 meters. This distance can be modified according to site conditions and the free operating speed. It can reach up to 400 msters on highways with good visibility and where the speed can be high. There are exceptional cases where two very near successive intersections can justi$ location distance shorter than i00 meters. 336
Distance Indication Sign
bstween the successive intersigns. Road signs are warning the including is variable sections preceding junction' the and intersection the located betwesn it is rounded to the 50 meters, When the distance is smaller than nearest l0 meters. On curbed roads, signs are located back from the face of the curb not less than 30 celrtimeters or more than
In Urban Areas, the distance
1.00 meter.
In Urban Areas with public illumination, tlre signs can
be
placed a|2.30 meters above the top of the curb. Where pedestriiilN or parking of vehicle is not allowed, ttre rural area rules are applicable. 337
Elements of Roads and Highwnys
Traffic Engineering
Sight Triangles
If possitrle, vehicle drivers should be given the best visibilconditierns. Thus, in deg road intersections, the Free Flow Operating Speed is considered, not the Design Speed. In approaching irrtersection, the drivers of two converging vehicles need enough visibilrty to see each other in time to prevent collision at the crossing" The sight triangle is associated to each conflict point between two vehicle fl,:ws. The summits of this triangle are the conflict point, and the limit from where the drivers must notice an adverse vehicle. ity
l||rr llrttt|t lltll trl.rilt
\\-
The signal GIVE WAY is applied only to the vehicles on the secondary road. However, it is necessary to check if the vehicles on the secondary road have the visibilrty corresponding to tJre execution at the crossing or insertion maneuver.
J6O
Forms of Intersection Signs
1. 2. 3.
Triangular in shape with one angle vertical. Triangular shape with one angle atthe bottom" Square and octagonal shape.
The triangular shaped signs with one angle vertical are following the general rules for warning signs. The triangular shaped with one angle at the bottom includes red border wider than the normal waming sign (x 1.333).
l--*-
l0-5 Prescription a,nn,
o'*r"n""
.o
FIGURE 1O-4 SIGHT TRIANGLES RIGHT PRIORIry
338
Sign
The Prescription Road Signs inform the drivers of the traffic laws and regulations that could be an offense to anyone who disregard and violate it.
Prescription sign is installed only with the approval of Public Authority having jurisdiction of the premises to be removed any time if the legal requirements of the signs become inconsistent with the prevailing conditions. 339
Traffic Engineering
Elements of Rosds and Highways Included in this classification are those signs that indicate removal of legal restrictions imposed by a preceding prescription sign.
ae
The No Left Turn - No Right Turn The turn prohibition is applicable at the next intersection. The signs can be completed by auxiliary sign M4 giving the category of vehicles.
Prescription Sign is Classified into Three Categories
The No U Turn This sign is used to notify the U-Turn prohibition up to the next intersection. This intersection is included in the prohibition.
Prohibitive Signs b) Obligation Sigrrs a)
c)
End of Prescription Signs
The prescription signs are circular in shape, but for regulatory purposes ofparking applied to a zone, the circte is placed inside a square.
1.
The Prohibitive Signs have a white background, red nng and prohibitive red bar, symbols, and letters. Numbers are dark blue except the srgn R3-l vvith red background and the Signs R5-10, R5-12 with a dark blue
The No Overtaking Sign The R3-16 sign signifies the drivers that it is prohibited to over any Vehicle except the two wheel vehicles without sidecar. The R316 sign must be completed by continuous line marking on the pavement.
@@
Stop Contrcl The R3-17 sign is used to notify the proximity of a control point where the vefricle has to stop. The sign is divided into two by a dark blue horizontal bar. On the superior part it includes the word STOP and below it is written the nature of the control or the reason of the required stop, which can be Police, Custom, Health, Toll, etc.
background.
The NO ENTRY sign has only white border. The background is red with a horizon*,al white bar.
ln order to
improve the legibility, only the following signs
includes transversal bar.
* No Left Turn, No Right Turn, No U Turn * No Stop, No Parking * No Use of Audible Warning Device D=85cm
Prohiblted Traffic The sign RO indicated that atttraffic is prohibited on both directions for all vehicles.
No Entry for all Vehicles This sign R3-1 indicates in the beginning of the one way road that the vehicles can only circulate in opposite direction. lt is necessary to repeat this sign on all intersections along this one way road.
340 I
]'
Prohibitive Sign FIGURE
1O-
End of Prohibitive Sign
5 MEASUREMENT OF PROHIBITIVE SIGNS
341
Traffic Engineering
Elernents of Roads and Highways
10-6 Obligation Signs
O
The meaning of the following Obligatory Direction signs
R2-l No €ntry for all Vehicbs
Prohibited Trafhc
No U Tum
@ @ No Parking
Prohibited to Cars
No StopNo Parking
@ @
No overtaking for vehicles whose weight exceeds 3.5 T
@
No left tum
Prohibited to trucks
No overtaking
- Obligation to continue straight ahead (R) - Obligation to follow the right direction R2-2 (L) Obligation to follow the left direction R2-2 R2-3 (R) - Obligation to turn the obstacle by its right side R2-3 (L) - Obligation to turn the obstacle by its left side R2-4 (R) - Obligation to turn right R2-4 (L) - Obligation to turn left R2-8 (R) - Obligation to go straight ahead or to turn right R2-8 (L) - Obligation to go straight ahead or to tum left R2-9 - Obligation to turn right or left R2-10 - Obligation to use the roundabout
No right tum
Prohibited to pedestrians
@
Prohibited to animal drawn vehicles
FIGI-.'RE
34)
10-6 PROHIB IVE SIGNS
FIGURE 10.7 OBLIGA'I'ORY DIRECTION SIGNS
343
Elements of Roads and Highways
Traffic Engineering The Obligation Signs are circular in shape. The background is dark blue. The symbols and border is white. If the istration enforces prohibition or an obligation sign, it has to inform the driver the end of this restriction to ttre highway use. For example; the No ing Zone, the No Parking Zone, the speed limit, the prohibition to use audible warning signal and others.
{-+ t-r.s
I
1-t 1gi \ !-i--_-_____
"t $q {o
FIGURE 10.9 OBLIGATORY DIRECTION SIGNS
10-7 End of Prescription Signs
n. La,/Ai iltl.,u -'. ---,
281 -ll
I l\
i
|
---f--
|
t---------.21.s -- ----__.1 FIGURE 1O€ MEASUREMENT OF OBLIGATION S|GNS
344
4
The end of all prohibition signs is also circular in shape and represents the sarne bar sign obligation symbol. A red bar from the right top to the left bottom cancels this obligation. The R4-2 informs the drivers of the end of all the previous prescriptions. However, it does not include the law that prescribes the national speed
limit. 345
Elements of Roads and Highways
Traffic Engineering
The R4 notifies the driver of the end of all particular speed limits other than those defined by the general laws, speed limits previously applied to all vehicles or only to one or several categories. The sign should not be setup on the road where tle speed limit is greater or smaller than tlle ones prescribed by the general rules. -
i:[1"''> ADVANCE DIRECTION SIGN
O
End of all indicated prohibition
BULACAN Ehd of speed iimil
End of overtaking prohibition
(R\
v
INTERSECTION DIRECTION SIGNS
End of prohibition limiting weight greater than 3.5 T
End of reserved lane for buses
End of prohibition using audible waming signal
FIGURE ,IG1O END OF PROHIBITION SIGNS
10-8 Direction Signs Direction signs are divided into four categories
l.
Advance direction sign Intersection direction sign
2. 3. Reassurance of confirmatory slgn 4. Entering and Exit of urban area
CONFIRMATORY SIGNS
TT" four categories are well defined in the philippine Road Signs Manual. In Europe, a different green is or"d- fo,
background of the sign. It is more intense with an emerard tint. ?.46
FtcuRE
r0-rr DrREcnoil stolts 347
Elements of Roads and Highways
Traffic Engineering The driver should be informed that he is entering the crty of CX) and to refrain from being attracted by anything except to look at the shop signs only to know where he is.
The sign EB10 is rectangular in shape with white background, red and white borders and dark blue letters. At ttre end of the city proper, another sign EB20 notifies the driver that he is leaving the place and that he can resume his speed under the traffic regulations. These two signs, limit ttre area where the attention of the driver is concentrated. Outside the city limit after the EB20 sign, the condition of driving will be different givtng the driver the signal to resume his speed.
Md-2
?*-
lrc
lri 2
10-9 Informative Sign The objectives of this sign is to give the driver miscellaneous information usefi.rl in his driving and general knowledge. The signs are square in shape with dark blue background, white symbols and letters bounded by white borderline. Informative signs may include red symbols and bar notifring the end of prohibitions etc. MC
MC
2
2
Material Requirements
FIGURE 1O-12 DIRECTION SIGNS STANDARD MEASUREMENTS
These green signs with white letters, bonrer and arrows are used for nafional highways. For expressways and freeways, blue background signs are used. The letter synnbols and bo.deis a.e
all white. For small rural roads, white backgrou"O black leuers, numbers and borders are used,
,ign. *iih
Entering and Exiting Urban Areas
It is necessary to advise all vehicle drivers that they are entering an urban area where the condition of traffic is diffeient. :48
Sign s for warning, regulatory and informative signs are manufachrred from aluminum sheeting of at least 3 mm in thickness. The Reflective Sheet used for road signs consist of spherical lens elements embedded in transparent plastic having smooth, flat surface with protective pre-coat adhesive which are pressure sensitive for manual application or tack free heat activated for mechanical vacuum heat application. The minimum brightress value of the reflective sheet compared to magnesium oxide should be in accordance with Table l0-2. The brightress of the reflective sheet when totally wet by rain should not be less than 90% of the given value. 349
Elements of Roads and Highways
Traflic Engineering
m
2.
tEl
,;;;"n
m Combrtrwn
End offteeway
4.
The reflective sheeting should be flexible to permit application and adhesion to moderately embossed surface. The sheeting should be solvent resistant capable of withstanding cleaning with petrol, diesel fuel, mineral spirits, turpentine or methanol. It should be weather resistant without discoloration, cracking, blistering, peeling or any dimensional changes. The sheeting must show no cracking or reduction in reflectivity after dropping a 25 mm diameter steel ball from a height of 2 meters into its surface. The adhesive should permit the reflective sheeting to adhere accurately 48 hours after application of 90"C temperature.
Picnic area
Hospital with emergenqy servi€
Ferry boat
m Priority to this direction
TABLE 1O-2 RtsFLECTIVE BRIGHTNESS OF TRAITTC SIGN SURFACE
Mnimum Rcfl cctivc Brightrrcss
Valrr comparcd with MgO 0.5" 0.50
0.5" 0.5" 0.5" 0.5" 0.5" 0.5" 0.5"
No through road
FIGURE
350
One way
Perting
1S13 VARIOUS INFORi'ATIVE SIGNS 351
Elements of Roads and Highways
Placement of Signs
Traffic Engineering
4.
The position of individual sign depends upon its purpose and circumstances peculiar to its location. If possible, iocation should be standardized. Positioning provides another set ofcues to motorists. The Manual recommended the right positions for all situations to wit:
l. 2. 3. 4. 5.
Warning, Regulatory andAdvisory signs for rural roads are mounted 1.80 to 3.60 meters from the pavement edge with the bottom of the sign 1.50 meters or more above the roadway. On high-speed roads, warning signs are posted as much as 450 meters ahead of the hazards. Rural road warning sign distance should be placed about 250 meters and75 meters in urban areas. A horizontal clearance not less than 60 centimeters be_ tween the curb face near the edge of the sign a minimum height of 2.10 meters above the curb is prescribed where vehicles may park along the curb.
Sign positioning must fall within the driver,s field of view so that drivers may not be looking away from the
5. 6. 7. 8.
they must appear in the
headlight to be effective at night.
10-10 Traffic Signals Traffic signal is defined as all power operated traffic control devices, except flashers, signs and markings for directing or
1. 2.
l. 2. 3. 352
Provide orderly movements of traffic. Increase the traffic handling capaclty of intersections. Reduce the frequency of certain types of accident.
Interrupt heavy traffic to permit crossings by other vehicles or pedestrians.
Control the traffic lane use. Provide ramp control at freeway entrances. Intemrpt traffic for emergency vehicles and at movable bridges.
Excessive delay to motorists and pedestrians.
3.
Disobedience to signal indications and other particular installations. Diversion of traffic to less advantageous and undesirable
4.
routes. Increased accident frequency like rear-end collisions and pedestrians.
Signs and directions are enforceable only if they are installed under legal authority. Model legislation is found in the Uniform Traffic Laws and Ordinances.
Traffic Signals are Classified into:
l.
warning motorist cyclist or pedestrians.
Each of these different types of signals.serves as one or more of the following functions:
speed.
The belief of la1'rnen and public officials that traffic signals could provide solution to all traffic problems, has led to the numerous unsuccessful installation of traffic signals. The unfortunate results of unplanned installations of traffic signals are:
roadway.
6. If the signs are not illuminated,
Coordinate traffrc under conditions of favorable signal spacing so that it flows nearly continuously at definite
2.
Pre-Timed Signals - where traffic time intervals are divided to the various traffrc movements.
Traffic Activated
-
where time intervals are controlled
as a whole or in part by traffrc demands.
Modern signals are electrically operated. Individual units have separate red, yellow and green lenses with 20 or 30 cm. diameter each has its own light sources. The 30 cm. lens is specilied for irtersections where 85% speed exceeds 60 km. per 353
_ i
Tralfic Engineering
Elements of Roads and FlighwaYs
hour for all arrow applications and for problem locations. Sig:' nals pedestal or brackets are mounted outside the roadway limit, sornetimes they are suspended above the intersections by cables, mast arm or other .
5.
Mounting Specifi cations
7
l. 2. 3. 4.
6. . 8.
'lhe recommended height for post-mounted signals from the bottom of the housing is 2.40 to 4.50 meters above the sidewalk or crown of pavement, if there is no side-
9.
walk. The minimum mountrng height is 1.35 meters. The minimum and maximum vertical clearance for signals suspended over ttre roadway is 4.50 and 5.75 meters
10.
respectively. For each through movement, two or more signal display of faces visible to approaching traffic is prescribed. This is to give the driver following immediately behind trucks a chance to see the signal indication as they approach the intersections.
@ @
@@ 354
Where signals must intemrpt fast moving traffic on expressways, the cornmon practice is to install three or four signal faces on each approach. Under special conditions like heavy pedestrian movement, school crossing, mid lock crossing arrd special rectangular pedestrian walk, the ..Dontt Walk" signs with either words or symbol message is extremely nscessary. For non-intersection pedestriar crossings, two signal
faces for vehicles are required augmented b1'
signs
pavement maikings and parking restrictions.
Positive Meaning of Each Color
1. The steady
2. 3.
Circular Green... Means GO Green Arrow..................,..... Go to such direction Solid Red light ... .......... Stop and wait for a green indication.
4.
Flash Red ...............,...."........M&ms an arterial Stop Sign 5. Flashing Yellow Means Proceed with caution 6. The use of Steady Yellow for caution is prohibited except as waming between green and red indication.
Location of Signals
1. A
distance of 12 to 36 meters beyond the top line for t'"ical right angle intersections far side by mast arm or cable zuspended locations.
2. If bottr signals are post mounted, install on the far side, 3.
FIGURE 1G14 TRAFFIC SIGNALS
Signals must be visible to approaching vehicles witb a distance ranging from 30 meters for an 85 percenule speed of 30 km./hr. to 21CI meters for 90 km. per hour. Where a continuous view of at least two signal faces are blocked by physical objects, warning sign is required. For an excessive t rnring lane, one slgnal face is required.
one on the right and the other on the left or median. The angle between the drivers normal sight dire,ction, either of the signal faces should not be more than 20o angle 355
-
Traflic Engineering
Elements of Roads and HighwaYs TABLE IG3 PARTTAL DATA ON RECOMMENDED ROADSIGN INSTALLATION PRACTICES* Minimum Dimension in Inches
Purpose
of Design Warning of hazard
Diamond
Triangular Black
Railroad crossing
Disk
Regulatory sign
Vertical
on
Ellack on
Yellow Yellow
36 (vert.) x 48 x 48
24 or
Rectangle
Black on White
height variable
Octagon
White on Red
Primary 30 x 30
Triangular
Red on White
sa€*
30'wide
Fis* F::*.o '5cc) ;T B e o.O
24x?A
36x36x36
Vertical
Rcd on Whitc or
Rcctanglc
Grccn on White
Parking - Rural
Vcrtical
Red on White or
Informational
Rcctangle Grcen on Whitc Horizonial Black on Whitc
Parking - Urban
E
?An
' =p E:8
x30"
Fr F.e to o9 rno Fx oo .^o
Whitc on Grcen Sccnic Rest
Route lvlarkers
"Be
spccial
3g
Shield
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8
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35
Rcctangle
3; 5q
r Based on Manual on Uniform Traflic Control Devices
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Road Markers
interstate
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Horizontol White on Grccn Rcctanglc
Recreational
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No ing zone
Stop sign
g 5 ()
Traffic Engineering
Elements of Roads and trIighwaYs
4.
'l"he Uniform Vehicle Code prohibits illuminated advertising signs that interfere with the effectiveness of traffic control devices. The Manual recommended that local government legal authority should prohibit them.
Signal Control
A solid-state mini-processor for intersections control must be available. The mini-processor receives inputs from detectors, and interprets their meaning, then select the appropriate set of signals from those in the processor's memory bank These devices can accept thousands of instructions per second and respond very quickly to any changes in the traffic. The advance miniaturization systems make it possible to combine the advantages of pre-timing coordinated movement and tlaffic acluation in a single or area wide intersections to reduce cost and delay. Today, most detectors consists of wire loops installed under the road surf;ace that the presence of vehicles through changes in their magnetic fields. A more sensitive series of loops recording the number of vehicles waiting to m:,k-e a maneuver. Transverse and loops are sometimes installed diagonally in part to detect the presence of motorcyDeg an effective detector system is not easy because the location of detector loops in relation with the stop line depends on the traffic control plan. The detector is somstimes placed at a distance from the intersection where vehicles on the main road are approaching at high speed and expectrng to continue through. Another close-in detector is installed to prevent entrapment at the stop line or to extend the green signal time. The distance where detectors are installed ranges from 55 meters for 45 kmftr. to 135 meters for 90 kmihr. speed.
6.
road, pedestrian needs, zurd vehicle speed approach. Thc Traffic Manual recornrnended that dre total time allowed for pedestrians should be an initial interval of 4 to 7 seconds to start plus walking time computed at 1.20 meters per second" On wide streets, pedestrians rnay be stopped on medians at least 1.80 meters wide. However, a separate pedestrian signal activator must be installed on this median if pedes-
trian push button is incorporated in the overall control system.
Ordinarily, the time required fbr cornplr:te sequence
Under normal traffic volume, coordinated signals at various intervals estimated from 750 meters to more than a kilometer is effective in making smooth flow of traffic. On the contrary, when the street is loaded to capacity, coordination of signals is ineffective in making smooth traffic flow.
The four systems of coordination are:
l.
Cycle Length of Signals
358
5"
Synchronized Movement
cles.
l.
indications fall betrveur 30 and 120 seconds. To reduce delay of strnding vehicles, short cycle lengths are adopted. Holever, a relatively high percentage of the total time is consurned in clearing the intersections and starting each succeeding rnovements. 2. A larger cycle increases the percentage of time lost. For high volurne traffic it is necessary to increase the cycle length to gain additional road capacity. 3. Approximately, one vehicle can each traffic lane with normal signalized section in 2 second of green light. 4. The yellow inten'al following the green signal is usually between 3 to 6 seconds depending upon the width of the
of
Simultaneous coordination
2. Altemative coordination 3. Limited progressive 4. Flexibleprogressive
359
Elements of Roads and Flighways
Simultaneous coordination makes
all color
Traffic Engineering indications
along the street alike at the same time. It produces high vehicle spoed between stops but have low overall speed.
ln Alternative Coordination, all signal changes their indication at the same time, but adjacent signals along the street show different colors. This is fairly well on a single street that has approximately equal block spacing. [t is also efFective in controlling traffic in business areas several blocks on one side trut only when the block lengths are approximatd equal in both directions.
The Limited Progressive System retains a common cycle length providing separate "GO" at each uttersection to motor traffrc progression. This gives continuous or nearly continuous flow of vehicle group at designated speed in one direction and discourages speeding between signals.
The Flexible Progressive System is provided with a master control that commands the controller for the individual siguals. The systerns give proper coordination between signals and make prcdetermined changes in cycle length, cycle split, and offsets at intervals during the day For example, the cycle lenglh of the entire system could be lengthened during peak hours to increase the road capaclty and shortening other time to decrease delays.
10-1
I
Pavement Markings
The early road marking was first introduced in Wayne Country of Michigan in the year 1911. After a decade, pavement markings gained universal acceptance.
Pavement marking was introduced to delineate 1. Roadway centerline 2. Lneboundaries
4. Pavement edges 3. No ing zole 5. Roadwaytrar:sitions 6. Tumingpatterns 16()
7. Approach to obstruction 8 Light rail or bus clearance 9. Stop line 10. Cross walks 11. Railr
To be respected, pavement marking should be simple, easy to understand, well designed and properly located. tn ttre prrii, ippines, 80% of the drivers do not respect the horizontal mark_ ings because it is too complicated. For example:
l. 2. 3. 4.
The continuous white line Simple continuous yellow line Double continuous yellow line
Broken white line bordered by two continuous yellow lane
What is the barrier line? The 1968 Vienna Convention gave the answer: A continuous line must not be crossed. It ii an imable wall All other broken lanes can be crossed with or without care
Specific Use of Colors
a) White is used where vehicles may cross the markings like
l. 2. 3. 4.
Lane lines Pavement edge lines
Channeling lines Turn markings
5. Stop lines 6. Cross walk 7. Parking space limit line 8. Words and svmbols
b) Yellow Lines delineates the separation oftraffic flows like
l. Center line oftwo highways. 2. Double centerline for multi-lane roadway. 3. No ing barriers or zones of two and three lane road 4.
and road transitions. Channeling a c€rrter lane
5.
vided multi-lane highways. Obstructions must be ed to the right.
for two-way, left turns on undi_
361
Traffic Engineering
Elements of Roads and Highwavs
c)
Dashed Lines for directional line such as center strips on two lane highways and lane lines. The ratio of the stripe to gap is I to 2 stripes - 3 meters long and 9 meters gap is recomrnended for rural roads. Excessive use of continuous lines should be avoided when it leads to the creation of artificial traffic bottlenecks or to a noticeable decrease ofthe capacrqy on an important length of road. The Rules State that:
l. A
contirurous line shorild not be placed in sections where the visibility is greater than the minimum lengfh
2 3.
for ing. There should be no continuous line in the sections w'here small width of travel way hinders the drivers to respect the continuous lane.
'[he length of contimrous line is strictly limited to the indispensable length. The minimum length is: 30 meters rn rural area and 20 rneters in urban areas.
The beginning of a continuous line must be designed not to surprise the driver. Drivers must understand the reason of the continuous line. For instance, the long straight line along a wide
bridge on flat area where the driver cannot understand the purpose of such continuous line. The driver will not respect instructions that he does not understand. Nexl time when the continuous line is necessary, the driver will ignore the waming and cross the line thinking once again that this line is only a landscape for beautifi cation. For urban areas, short length may be appropriate. On the contrary, yellow barrier lines and white guidelines are generally continuous on where crossing is to be discouraged. The recommended stripe width is 10 to 15 centimeters, and for emphasis, a stripe double the usual width is recommended.
Requirements for Ideal Road Markings
l. ?62
It must be cheaper to install
2. 3. 4. 5.
Should be permanent
Must be readily visible day and mght, rain or snow. Even with water standing on the pavement, the surface markings should clearly transmit to the motorist the intended message.
Marking should not be destroyed by snow or dirtremoving equipment.
The Paint Materials for Striping
l. 2. 3. 4. 5. 6.
Modified alkyd resin with Titanium Dioxide (white) or Lead Chromate (yellow) pigment. The paint film thickness should be in a range of 0.015 inch with about 60% solid. The paint coverage should be about one gallon per 100 meters of continuous i0 centimeters stripe. In addition, 2 tD 3 kilos of glass treads with an average diameter of 0.5 rnm per gallon is added to the paint or
by drop-in during application. Re-striping (re-painting) frequently depends on a variety of factors reported to be as frequent as 3 times per year where traffic is heavy. Paint must dry after application at the rate of less than 60 seconds and not more than 3 minutes.
Other Markings:
A raised reflector less than I rnch in height illuminated by vehicle headlight is widely used. White color is used for lane marking, bhre color to outline bicycle lanes and red to fucrng vehicles traveling in wrong direction to the freeway entrances or exil rnmps. The raised reflector creates rumbles on running vehicles when it crosses the line or tray on it. These devices are mounted on the road by means of epoxy. The disk or reflector serves to alert inattentive drivers. The large mushroom button type was one time employed as pavement markings but their use are found to be objectionable. 363
Elements of Roads and Highways
Traffic Engineering TABLE lOS COMPOSITION OtrPAVEMENT PAINT SOLVENT
I
,if rli
Raw Tung oil Normal Butyl Alcohol Aoctone (dimcthyl Ketone) Dcnatursd Alcohol (Formula No.
I
t (o
l)
15
o/o
l7
o/o
34
o/o
34%
Thc alcohol and acctonc are mixcd first thcn thc oil is addcd to form a clccr
,f
solutionat2loC.
I
l.r ,f i,,l E I 1
i I
I
I g
I T, ill :! l,l TJ ,ii
r +'
TABLE
EEE ililll :J5
I
---tI I I
q o
R
I
Ess.c i':'t
I
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I
I
I
rgg !P!.g
E.g,.c, I :lI
Titanium dioxidc (anatasc ) Mcdium Chromc Ycllow Para Toncr ( liSht ) Extondcr
TABLE lOE COMPOSITION OF?NNT
co T .C
i I
Compositionby Weight %
: ;o
E
I
I il ,ill "i ll _l
TABLE I(}7 COMPOSITION OFPAINT PIGMENT
tr.c
I
I
ES€ KEE
988 Qn v
i I
(!
a
ITT I
I
I
r-i-r-l-ri-t
I
8
I
I
COMPOSITION OFPAINT VEHICLE
p88
I
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II}6
l
Compositionby Weight%
co
J
Pigmcnt
Vchiclc
4245Yo 5*58c/o
23o/o
77
o/o
NNOoa
l. Para toncr to standard shadc 2. orrc part by volumc and I acctatc is addcd to lfi) parts paint 3. Sultcient Prussian bluc is addod to thc raw tug oil for thc whitc paint FIGURE
354
1Gl5
BROKEN LINE TYPICAL MODUI.ATION
to ovcrcomc its vcllowish tint.
365
Traffic Engineering
Elements of Roads and Highways
Words, I-etters or zurows are also placed on the pavement to notify the motorists that they are approaching hazard zone Such as railroads, school crossing, or to mark straight through or turning lanes. Symbols, words or numbers convey information such as Speed Limit and the nearness of schools, hospitals, judiciary courts, etc. Pavement markings have been proven effective in the reduction of accident, and much is yet to be learned ofdriver's response.
Paint should not be applied on wet pavement and during damp weather, or when the air is rnisty. Application is preferably by machine but where brush is used, only round or oval shape not exceeding 10 centimeters width is permitted.
Ballotini for Reflective Road Paint
For punctual obstacle like the curb of bridge sidewalks shall marked be by one or several reflectorized dwice. The color is red if the obstacles are on the right side, white or yellow if they
Ballotini consists of beads of good quality, optically clean, lead free glass with not less than 90Yo spherical and free from flaws. The beads contain not more than one half percent of foreign matter free from flowing under normal atmospheric condi-
Traffic paint is applied producing a uniform even coating in close with the surface being painted. It is applied to the pavement at the rate of 0.33 liter per square meter and dried sufficiently and free from cracking from 15 to 30 minutes.
are on the left side.
Reflective Pavement Stud
tions. TABLE IG9 GRAI'ING OF BALLOTIM US Standard Sieve
mm
Inch.
Percentage ing
by Weight
l.l8
No. 16
100
0.85 0.60 0.30 0.18
No.20 No.30 No.50 No.80
65-75 45-55
t2-25 0
For proper light reflection, the proportio.n of ballotini to paint should not be less than 45 kg. per liter and not more than .50 kg per liter of mixed paint. In cities with street lighting the use of reflectorized paint is not necessary. Thermoplastic materials with or without reflective properties can be used in locations subject to extreme traffic wear. The service life of this material is five times that of beaded trafhc paints.
3(6
Reflective stud is either Flush Surface or Raised Profile type with the fol lowing characteristics :
L
The Flush Surface R.eflector short base type measure 120 mm x 140 mm. The base is formed on cast iron with adequate webbing to insure a firm key to the road when installed. 2. The pad is highly resilient and durable rubber reinforced with canvass des:gned for at least 5 years. 3. It is designed to produce a self-wiping action of the reflectors when depressed. 4. The reflector is made of impact and abrasion resisting glass hermetically sealed into a copper socket. 5.
6.
The Raised Profile Reflector consist of acrylic plastic and shell filled with an epoxy compound molded from methylmethacyclate into the shape of a shallow frustum of a pyramid with base dimensions approximately 100 x 100 mm and thickness not more than 20 mm. The shell contain two prismatic reflectors, each inclined at an angle of30o to the horizontal and having an area of not less than 20 cm2. 367
Elements 7.
of
Traffic Engineering
Roads and Highways
The Reflectors minimum specific intensity values expressed as candle power per foot candle of illumination at the reflector on a plane perpendicular to the incident light givur in Table l0-2.
8.
Cement Mortar shall consist of one part portland cement to two parts fine aggregates mixed wrth water.
Advance Marking
Each reflector for testing is located at the center of the reflecting face at a distance of 1.50 meters from a uniformly bright light source having an effective diameter of 5 mm. The width of the photocell is 1.2 mm shielded from stray light. The distance from the center of the light source and photocell is 5 mm. Failure of the reflective faces more than 4% could be a cause for reiection of the complete batch. TABLE IO.TO RAISEI' PRONLE PAVEMENT STUDS PHOTOMETRIC PR.OPERTIES
Divcrgence Anglc Incidcncc Angle 00 200
0.2"
.oo-_=-
1.O0
0.75 0.30 SELECTIONARROW
The reflector shall a vertical load of 1000 kg (kN) when tested in the following manner:
l. 2.
The reflector is centered horizontally over ttre open-end to a vertically positioned hollow metal cylinder, 75 mm internal diameter 25 mm high and 6 mm wall thickness The load is applied to the top of the reflector tluough a 6 mm diameter by a 6 mm high metal plug centered on top of the reflector. Failure shall constitute either breakage or significant deformation of the marker at any load less than 1000 kg. per foot.
Adhesive. When Raised Profile type reflector is specified an approved epoxy adhesive is used. 368
so -
.os
;24
HQhway or lane axis
R=21
1.12
__
a.g) _
f- .r,1.lss--l ----1 l--
6.O0
I
FIGURE .IO-16 RETURN TO LANE ARROW
369
Elements of Roads and Highways
Traffic Engineering
\
.:os
,\
\\^Tl*'
I arr
r3r
l|f|l||trt ttartr al ttsarttrY rtll
l_
r.---:r '
-l - ,. -a -L.. -<-!F:_-11.3v__ 6
?
FIGURE tO-17 TAPER tetARKtNGs
r
t
_
FIGURE lO-18 DtVtSlOfttAL tSLAlitD Ot{ SECOIDARY ROAD
370 371
Traffrc Engineering
Elements of Roads and Highways On two-lane highways, all continuous lines are preceded by warning broken lines. The line must be completed by Return to Lane arrows. At the approach of the continuous line and in the case of reducing the number of lanes, the use of Return to Lane Arrows is compulsory to incite the driver to use the indicated lanes.
lfre arrow overlaps the warning line. On multi-lane highway, the arrows are sst out on the axis of the lane to be suppressed generally by the left lane in the considered direction. The number of arrow is normally three. In urban area it can be reduced to two. On certain exceptional cases like sinuous roads, the number could be increased to 5. The advance selection warning and the identified position can be on selective cases in urban areas by painting an Eurow on the pavement called selection arrows asg each lane to one or several directions. The use of these arrows is to limitthe left tum and right turn specialized lane.
There are Six Types of Guideposts or Bescons.
l. Curve guide post 2. Intersection guide post 3. Hazard marker 4" Nose Marker 5. Delineator 6. Wind cone Ref,
Jl J3 14 J5
J6
J7
€crtorized red materials
(t
N _t
o o I I
10-12 Guidepost and Markings Guideposts are set to guide the drivers and to pinpoint a particular or linear danger.
CIRCUI.AR SECTION
SQUARE SECTION
FIGURE 1O-20 SECTION OF CURVE GUIDE POST J1
zs ,/ .----.| 20
--t I
130
I
80 I
CIRCULAR SECTION
FIGURE 1O-19 CURVE GUIDE POST J1
372
I
SQUARE SECTION
FIGURE 1O-21 INTERSETION GUIDE POST J3
-1
/-t
Elements of Roads and llighways
Traffrc Engineering
Non- rcllective dark Hue
l. bI o o\ Nt J o-'
---l I I I I
E
Ref,eclive white
o @
FIGURE 1O,22 HMARD MARKER J4
,"""",""r1
Shoulder Non refiective dark btue
Reflective white 30"
--<'
.
F-f:
FIGURE 10-23 NOSE MARKER J5
I
11
Delineators Delineators are light reflecting devico mounted on posts at the side of the roadway in series to guide the driver along the proper alignment.
FIGURE 10.24 DELINEATOR POST J6
4.
least on one side of the ramps.
Specifications:
1.
2. 3. 374
ln straight alignment, tlre spacing betwoen delineators is 30 msters and the same interval is observed in curve with 300 msters radius or more. For smaller curve; 20 m. spacing with radius between 150 and 300 meters, l0 m. spacing on curve with a radius less than 150 meters. Under normal atmospheric condition, it shall be visible at a distance of 300 m. under the upper headlight beam.
Delineators are specified on the right side of expressway and freeways unless these are fixed lighting and at
For edge lines the color must be the same. Red reflectors may be installed on the backside of ramp delineators to tell the driver that he is going the wrong way. 6. It is recommended that they should be used on two-lane two-way road. The recommended spacing is between 50 to 150 meters or tangents. 7 It must be progressively smaller on approaches to curves with minimum spacing from 6 meters with 15 meters radius to 30 meters with 300 meters radius. 5.
375
Elements of Roads and llighways
8. 9.
Traf,fic Engineering
Single delineators may be installed on the left side q'here the road is curving to the right.
On freeways, two yellow delineators at 30 meters on center is specified along acceleration lanes. Roadway narrowing should be marked for their full length. 10. Where curbs projects into the travel way, their ends shall have yellow reflectors if traffic moves to the right, white if it is to on either side.
Whatever type is used, delineator is called single face if it has one reflectorized device and double face if it has two devices. The single face is used on one direction travel rvay and the double face on two directional highway.
rng the distance from the crty of Rome to other principal cities were ftrund. Today, kilometric markers were insialled to assist the rnotorists in estimating:
l. 2. 3.
Travelprogress Pinpointing accident locations Distinguishing the positions of structures such as bridee
4. 5.
To identify road sections for cost ing purposes. To designate where maintenance is to be done.
and culverts
Raised bars are sometimes called "Jiggle Bars" used as charurel device at the nose of traffic island to keep vehicles out of certain paved areas. They are lower than the curb made of concrete or asphalt painted or reflectorized sometimes set diagonally to the vehicle way oriented to direct it back on to the right course.
Rumble Strips Rumble strips'are installed across the roadways to alert the motorist as they approach a dangerous situation like stop signs or abrupt changes in the oncoming alignment, grade or profile. Rumble strips are specially designed to create roar in the running vehicles.
Distance Marker
At the side of the roadway, kilometric markers are installed at every 1000 meters distance. These markers are usually made of reinforced concrete indicating the number of kilometer disumce from and to a specific place. The origin"of this marker was traced to have started as early as the Roman tirnes. Early markers were large upright cylindrical stone monuments show-
FIGURE 1O-25 DISTANCE MARKER
10-13 Griardrail Guardrail is generally designed to prevent a car from leav_ or from colliding against an obstacle by deflecting it so that it continues to move at reduced velocity along the guardrail and in tle normal direction. Guardrail is disigned to stop vehicles whose weight is smaller then lg00 kg. The need for guardrails on fill is related to the slope and height of the embankment In the Philippines, guardrails are not properly set and they may constitnrte additional road hazards than safetv dences. For instance: rng the highway
376 3'17
Elements of Roads and HighwaYs
Traffic Engineering
of the guardrail sections are not equipped with proper protection thereby constituting a kind of sword or battering ram which can penetrate inside t}e car during an impact. Sometimes the rails are mounted too high becoming seriously hazardous that could enter into the vehicle and The beginning
End of section
2.
decapitate the car occupant. 3.
4 holes 2.7 x 3.75
The superimposition of the different elements of the guardrails is done in the \ryrong direction. During an impact, the element can be flaked off endangering the motorists.
Elemcnt lenglh
Eeginning of section
E
43.10
End
of lcctiong
holes 2.3 x 2.8
Other Setup Arrangements Making the Guardrail Absolutely Useless
1. 2. ELEVATION
3.
Hole 17 x 50 Bolt 1.6 x 4.0 TH
Bolt 1.6x4.0TH
Oval
hole2x6.3
lr ll
8.2
L
6olt # 16 8 holes 2.3 x 2.8
Pcst
C
25x 50 x
100 x
5.
182
50x25 x'i
6.
Guardrails were fixed on the post transmitting directly the energy of impact to the that cannot sustain the shock. When the barrier collapses, the vehicle es over easily.
The holes and bolts used were not in accordance with the design and specifications. The s are sometimes located very near the crest of the slope. The foundation is weak to prevent the post from being tipped offduring an impact. Guardrails are frequently used to protect the structures, direction boards and traffic signs but not the drivers. Guardrail is used perpendicular to the flow of trafEc in the shoulder or in the median to protect a manhole. In case of impact, the economic cost of car damages will be greater than the cost of ths manhole repair. Guardrail is often used to replace the J4 marker or barrier.
t0-14 Concrete Barrier
OVERTAPPING DETAIL
FIGURE 10-26 GUARDRAIL TECHNICAL DISCRIPTION
378
The concrete barrier was introduced in the USA. n 1972 under the following conditions:
It
was
tested in
379
Traffic Engineering
Elernents of Roads and Highways
l. 2.
For light vehicles the impact angle of 30 degrees at a speed of 80 kn/hr" For 10 tons truck with impact angle of 20 degrees at 70 kmlu.
After two years of testing in real conditions, this tlpe of Separator was authorized rn the entire road network of . In 1977 it was used in USA, Canada, Sweden, Belgium, Germztrly, Ivory Coast and Morocco. Record shows that no cal or truck has ever crossed this kind of seoarator or trarrier.
Functions: The concrete separator is a rigid retaining device. It does not absorb kinetic energy by its own deformations:
a) For light vehicle weighing less than 1800 kg it's function is dependent on the angle of impact. If this angle is small, the section of the separator acts on the tires to guide back the vehicle to the travel way without serious damage. On the other hand, if the impact angle increases, more damages will be visible. The impact energy is absorbed by friction and deformations of the car body.
b) For heavy vehicles werghing 12 tons or less, in case of impact, the inertia and adherence to the ground of the separator will prevent the crossing by guiding back the truck to the right trajectory. c) For heavy vehicles weighing more than 12 tons, the separator functions effectively if the impact conditions are not very hard ( low speed, small angle.) If the separator is constructed on top of an embankment, the distance between the front face of the separator and the begin-
concrete bed if reouired Concrete bed if reauired
ning of the rounding should be equal or greater than the width of the separator itself. It is necessary to design a supplementary anchorage, concrete bed or a reinforced foundation beam. 1 m. min
FIGURE 1O-27 CONCRETE SEPARA'TORS
The separator can ensure double functions: as guardrail and as barrier. The double concrete separator was designed to be set-up on medians or shoulders. The single type has a reduced section and its use is limited to particular cases. The concrete separator being solid and rigid device camot differential settlements. Thus it must be set up on stabilized ground in order to eliminate the risk of rupture.
r80
FIGURE 10.28 LOCATION OF SEPARATOR4 ON MEDIAN
381
Traffic Engineering
Elements of Roads and Highways When the wall is set on the centerline the width Lensth Median is: the
of
L=0.60m+2d
for longer trips. In fact, these arterial roads are existing highway of considerable length wherein cross traffic is regulated by signals and stop signs. These arterials provide access to adjacent property with restricted entry and exit locations, street parking, cross center left turn and other difficult traffic activities.
Two separators can be designed to reserve place for planting.
L > (2 x 0.48) + 2d + e for the single separator L > (2 x 0.60) + 2d + e for double separator e ='the width of the planting area. 0 .32
traffrc volume exceeds 20,000 vehicles per day.
Basic considerations in planning arterial roads
l.
0.20
Selection ofconvenient route
2. Studies oftraffic volume 3. Origin and destinations 4. Accident experienced
15
3 continuous round bars High adherence steel 12 mm dia.
Arterial Streets are considered substitute for a controlled access when
15 15
Planning Criteria
l.
Arterial road should be at least 15 meters wide.
2. Must carry at least one lane of traffic in each direction. 3. It should be at least one kilometer in length. 4. It must skirt the neighborhood areas and not just penetrate them. Possible concrete bed
5. It should be spaced about 6.
FIGURE 1O-29 CONCRETE HEAVY BARRIER DOUBLE FACE
10-15 Highway and Urban Street Operations Prior to the existence of Freeways and Expressways, Arterial streets were the main way of trafific. Arterial and local street operations make use of street marking signs and signals controlled in several ways by either fixed setting or computerized system. Despite the existence of freeways and highways, arterial roads serves the major traffrc flow to the nearest access points because arterial roads offer the most advantageous route
382
600 to 900 meters apart from
grid type street pattern. The minimum volume to justi$ arterial road is 300 vehicles per average hour during the day and 450 vehicles per hour during peak periods.
There are times when the traffic volume exceeds the capacrty of the arterial road of conventional two way street during peak hour and to unload and increase the capacity of the road, the followin g solutions are employed:
1. 2.
Parking is strictly prohibited during peak hour on one or both sides of the street. No parking is allowed several meters away on each side of intersections. 383
Traffic Engineering
Elements of Roads and l{ighways
3.
Allowing right turns on red signal or providing special
4. 5.
provisions for these turns outside through the lanes. Eliminating left turn at congested intersections. Reversing the flow of traffic in the center lanes to accommodate more lanes in the direction of heavier flow.
One Way Street One-way streets are those where traffic moves in one direction only. Making one-way traffic is based on the number of important advantages over the two way operation such as:
l. 2. 3.
Bigger Capacity. More vehicles are accommodated by the same street system. Fewer Stops and Increasing Speed. Fewer delay at intersections because the number of possible conflicts were substantially reduced. Improvised Pedestrian Movement. One crosswalk is totally free from turning vehicles durmg each phase of the signal at signal-controlled intersections of two onewav streets.
4. 5.
Ihe idea of making a street one-way to traffrc have meet oppositions from the business group and others who fear adverse effect on their interests. For instance, the travel distance to reach a certain location is often increased, a condition that seriously affect a particular business. There were inslances when due to strong objections the plan to convert the street into one-way traffic was aborted forcing the crty officials to give in after public hearing. The one-way preference streets in pairs could be an altemative.
10-16
way )
one-way two-way
One street One street (11 conflicts)
Both streets one-way ( 6 conflicts)
FIGURE ,I0.29 CONFLICT BETWEEN VEHICLES IN INTERSECTION OF TWO LANE STREETS; 2-WAY AGAINST ONE WAY OPERATION
384
Traffic Control
The most important traffrc control device for street operations are the STOP and YIELD signs and the Traffic Srgnals. The Manual calls for Two Way Stop on the less important two intersecting street where reliance on the right way, high speeds' or restricted sight distance indicates high accident hazard. The manual further states that multi-way (4-way) stop slgn installations should be used only where volumes on the intersection roads are approximatel;' equal' and only when any one of the following conditions warrants or qualification is met.
l. 2. Both streets two ( 24 conflicts
Reduced Accidents. When conflicts are elirninatecl' one-way operation reduces accidents of all types' Elimination of Headlight Glare. Ease of movement for emergency and less attention to traffic-
3.
As an interim rneasure when traffic signals are needed. When an accident problem ( as demonstrated by fve or more accidents in a year) can be corrected by multiway stop signs. When the total vehicular volume of 500 per hour enters the intersection in 8 hours or when an average dailv combined vehicular and pedestrian volume of 200 per hour from the minor highway I'rith an average delay of 30 seconds to minor streets.
Sometimes there are request from the public and its local
-?
85
Elements of Roads and Highways
officials to install stop signs where the condition does not warrant its placement. Example: a four way stop sign installed have been used where they could not be justified economically or on records ofaccident.
The Yield Sign could be a compromise between the full stop and no control. The Traffic Manual recommended its use under the following conditions:
l. 2. 3. 4.
That its bene{it include decrease
The Manual also provides minimum warrants for traffic sisnal installations based on:
l. 2.
Vehicular or pedestrian volumes. Accident experience.
3^
Progressive movement. Intemrption of continuous traffic to permit cross traffic to move as part of the network.
4.
Traffic Engineering Recommended Relief to Alleviate Congestions:
1. 2. 3. 4.
10-17 Freeway and Expressway Operafions Freeways are designed for high speed, free flowing, low accident facilities and operate without hindrances from traffic
control. This type of roadway operates well because of their isolation from the surroundings with widely spaced access and barred pedestrians. However, because of its isolation. correction is difficult if congestion develops to the frustration of the motorists who have no information as to its cause and duration. Indeed, because of its isolation, it is difficult to call for and render assistance in case ofaccidents or vehicular breakdown. 386
noticed. It is better to delay the few motorists who wish to enter the ramp than those motorists traveling on the freeway. A sirnple soluticn to congestion on the ramp is to close the ramp completely before the flow on the freeway reaches critical level. That is, if the rate of flow reaches
a pre-determined level or by closing the ramp dunng
5.
peak periods.
The use of service roads or arterial streets parallel to freeways during peak hours would gain road capacity.
Motorist Problems on Freeways and Expressways
l.
Public pressure that forces the installation of stop signs and unrealistically low speed limit signs sometimes contributed to the increased number of accidents.
flhe most common cause of traffic breakdown is adding more vehicles on the ramp. Thus, ramp control is necessary to prevent the flow disruption. Entry erf vehicles on the ramp should be restricted or stopped when breakdown on the flow of the fieeway is
The motorists are completely isolated from the surrounding community. The ramps that they could exit are far spaced, and sometimes several kilometers apart: in rural areas, and toll facilities are separated in kilometers or more in urban districts.
2. Walking on freeway shoulders is very dangerous. 3. It is almost impossible to walk on elevated structures 4. 5.
that have neither shoulders nor walkways. Motorist would not like to leave their vehicles for fear of robbery and attack. Modem vehicles are now complex and diverse in design that repairs by the driver or ing motorists is
difficult.
Solution:
1. 2"
Highway patrol should provide systematic surveillance. Emergency radio or telephone installed at roadside. 381
Elements of Iloads and flighways Emergency vehicles and crews should standby on call
to remove obstructing vehicles as quickly as possible. The agencies concerned should detail patrol cars along the fieeways for immediate assistance to motorists
-Traf'fic Engineering
5. (;.
l0-18 Street Lighting With the exception of nraior dor,inlown afieries. itighr,,'ay amd strect lighting are generaiiy incoqrorated in tli,,: rJcsrgn tt: illuullnat* the roadway tc., provide seeing by silhonefle. When an obji:ct is seen darker than the background, discermrent is by silhouette.
On the other-hand,
if
the object is lighter than its back-
ground" seeing is a reverse silhouette" A person or object on an iiluminated roadway is viewed in silhouette because the obiect is darker than the surrounding background.
neis and underes.
Lighting Source
asrsl
tri!ntallation
Highrvay iighting adopf fhe new and more economical types high and low pressure serlium and rnetallic halide but the trend is torvard the use cf high i)ressure sodium with common wattage for ali l:ypes fiom 175 to 1000 watts^
Lum.in:rires as Street Lights has the Following Criteria
1.
Recummended practice: Instali luminaires at 12.00 meters or mor{: above the roadway, although at present, the predonr.nanf mounting height is between 7.50 and
2.
When mounting
The AASHTO publication on Informational Guide for Roadway Lighting, NCHRP report 152 recommended an average horizontal illumination level of 0.6 to 0.8 foot-candle when the light source is at its lowest output due to age or dirt. It means that the light or bulb is about 1.0 foot-candle at the time of installation.
[*"or fr*eways, the uniformity ratio is set at 3:l or 4:1. 'l-he unjftrrmitv ratio is the average illumination divided b-v the lolvest illumination. The Guide also recommended the right illumination level firr lorv mounted bridge, railings and walls of tun-
3.
10.50 rneters.
is high, a rnore uniform illumination
can be maintained even though units are widely spaced.
High mounting of lights reduces the blinding effects of glare.
The guide also recommended adaptation of lighting on the leaving end of continuously lighted freeway to provide for an eye adjustment to headlight illumination. The recommended lerrel of illumination for streets and hishwavs are based on the level of lamp output.
l. 2. 3. 4.
For expressrvays, the standard proposed foot-candle is 10. On residential 1.4 fc in intermediate and 2.0 in
L
5. 6.
downtown areas.
For sidewalks on commercial areas, the recommended level of illumination is 1.0 foot-candle. For residential streets the value is 0.4 foot-candle.
7.
The requirements for collector road facilities fall be-
8.
tween those for arterials and minor streets. 388
4.
Lurninaires distribute light to a definite pattern that suits particular conditions. For a higher mounting, the spacing could be in the range of 60 meters apart with fixtures mounted on both sides of the road. Unifonn distribution could be adopted at intersections. A symmetrical pattern is used when the fixture is rnounted at the center of the street or an asymmetrical fonn when mounting is near the curb. 'llhc normal practice is to suspend the luminaires over t}te roadway, sometimes on cables or mast arms extending outward from the roadside. For roadway interchanges, the trend is to mount the luminaires on high poles, as high as 45 rneters. I
t11l
Traffic Engineering
Elements of Roads and Highways
10-20 Highway Capacity and Level of Service
10-19 Street Parking l
'Parking on the street substantially reduces the capacity of the road. It creates congestions and confusions. It increases travel time and accidents of vehicles. Legally, the right of the goverffnent to regulate the parking of vehicles on the street was established when Lord Ellenborough a famous jurist of England irr 1805 assertedthat:
"The King's Highway should not be used as stable yard" He established the principle that: "Streets are primarilyfor the free age of the public and {;nything: that impedes that age, except tn an emergency is a nuisance that may be abated. "Parhng of vahicles even infront of one's owned praperty is classtfe,l as u privilege subject to control and not as a right."
The authority to regulate parking stems fiom the police power the right of the govemment to legislate in order to protect health, safety and morals. Under such principle, public officials are free within reasonable limits to establish rules to control parking on street and to set penalties against violators. TABLE TO.II HIGTNYAY CAPACITY Facility
Capacity in enger Car
The capacity of any element of the highway system is the maximurn number of vehicles wilh reasonable expectation o1' ing over tho section (either one or both directions) during a given time period under prevailing roadway and traffic conditions. Example of capacities for modem highway element is presented in Table l0-l l.
Defining Associated With Capacity Maximum Volume. Whcre traffic flow is likely to continue without breakdown and serious compositions. It follows that at capacity, the quality of level of service is far from ideal. Number of Vehicles. Capacity is stated in enger cars per hour. Trucks and buses in the traffio stream can decrease the road capacity substantially. Reasonable f,)xpectations. Values for capacity cannot be determined exactly due to the many variable that affect traffic flows, particularly at high volumes. Assigned values for capacrty are more of probabilrty rather than certainties.
One Direction Against Two Directions. Traffic is one direction flows independently from that of the other. On the other hand, on two and three lane roads there are interactions between traffrc in the two directions and these affect traffic flow and capaclty.
A
Freeway and Expressway away from rams and weaving sections, per lane per hour.....................
2,000
Two lane highways, toral in both directions per hour...
2,000
Three lane highways, total in each direction per hour..
2,000
Given Time Period. Traffic volume and capacity are stated in vehicles per hour but traffic flow does not vary unifo.rnly with time, volume and capacities. This variation within an how is expressed by a peak hour factor (PFm) This factor which is less or equal to one in the quotient of the hourly volume divided by the shorter period volume multiplied by the
1,800
Exomple:
A 3.60 m. lane at signalized intersections per hour of green signal time ( no interference and ideal...... progrcssion)
Source: The Manual, TRB circular 212
JYU
number of periods in an hour.
lf
the hourly volume is 1,000 and the highest 5 minutes volume is 100, the peak hour factor (PFf) will be:
l9l
Iraffic Engineering Blements of Roarls and Highways
1000
x
The ideal conditions for the roadway to have an uninter12 periods in one hour at 5 min./period
100
lQ =
l. 2. 3. 4.
0.85
t2
where:
60
min :
rupted flow must:
12
5 min
Prevailing Roadway and Traffic Conditions This includes physical features that affect capacity like lane and shoulder width, siglrt distance and grades. It also reflects changes in the character of the traffic stream.
Ambient Condition is weather relateo conditions that affect
If these conditions are not met, road capaclty may be reduced. Enumerated below are the factors that contribute to the reduction ofroad capacity and level ofservice.
l. 2.
capacrty such as rain, fog, smog or wind.
Level
of,
Sen ice
The level of service is conrmonly accepted as measure of the restrictive effects of increased volume. Each segment of the roadway can be rated at an appropriate level from A to F inclusive to reflect its condition at given demand of service volume.
I-evel A B=
D: C
E =-
p=
Free
flow; speed control by driver's desire^ Stable Flow; erating speeds beginning to be restricted: little or no restrictions on maneuver abiliry from other vehicles. Stsble Flow; speeds and maneuverability more closely restricted.
Approaches unstableflow:tolerable speeds can be maintained but temporary restrictions to flow cause substantial drop in speed. Littie freedom to rn:ureuver comfbrt and convenience flow. Volume near capacity. speeds in neighborhood of 45 km./hr. Flow stable: stoppage of momentary duration. Abihty to maneuver is limited. Forced Flow: low operating speeds, voiume below canacitv.
392
Have 3.60 meters lane and 1.80 meters wide shoulder. Road with flat grades. Sight disturbance unrestricted No trucks or buses plying the route..
3. 4.
Narrorv lanes and shoulders, and restriction on
edge
clearance.
Sharp horizontal curves create dynamic forces to which drivers react. Short vertical curve over crests or obstructions to vision on the inside of horizontal curves causes vehicles to slow down. Commercial vehicles like truck requires more highway space per vehicle than the enger cars.
Effects of grade on uphill road, makes desirable vehicle spacing for higher road capacity. T\e 3o/o to 7Yo road upgrades does not affect enger c:trs unlike cargo trucks that are markedly affected by steeper grade.
Weaving Section Weaving section is defined as the crossing of two or more traffic streams traveling in the same general directions along a significant path of highway with the aid of traffic signal. The Traffic Circle Rotary or British "Roundabout" is considered series of weaving sections placed end to end. Likewise, a partial and full cloverleaf interchanges are example of weaving section. Vehicle entenng the freeway must wsave witl those leaving the freeway.
establishing level of service for.design purposes, each highway agency establishes its orm guidelines composed of two elements:
In
39:l
Elements of Roads and Highways
Traffic Engineering
l. The traffic volume served. 2. To proportion the basic freeway, weaving
sections, r:rmps and rarnp junctions to accommodate this flor,v at the designated level ofservice usrng appropriate data
il
TABLE 10-12 ENGERCAR EQUryALENT OFTRUCKS ON FREEWAY UPGRADES Four Lanes
Six or More Lanes
Grade o/o
2
2
2
t0
20
2
2
a -t
a
2
4
J
7
4
4
4
4
7
i
J
9
9
8
8
5
5
t4
IA
4 6
9
6
6
l3 l0
6
28
l8
!8
20
17
TABLE 10-13 LIMITING VOLUMES IN ENCL,R CARS PER HOT:R r.OR FREEWAYS AND ON AND OFF RAMPS FOR VARIOT,]S LE\'EI-S OF SERVICE AND PHF OF
T.OO
Freeway Volume in One
of Direction* Servicc Four lanc Levcl
A B c D E
Checkpoint Volumes Eight
lane Mergctr
Wcave
l)ivergesrtr
1600
3280
7fi
800
2500
5400
1200
3400
6800
15m
300 1650
Voluntet | * 1 500 700
1
1
300 550
3850
7700
1800
1900
1
(capacity) 4000
8000
2000
2000
2000
F"
Highly variable
Sourcc: TRB Circular 2 l2
t For 70 mph frccway dcsipln s1rccd tt Lane I volumc plus rarnp volunrc lirr onc lsnc ()rl rsnlps rtt 2 volume imnrcdiately upstrcarn ol'oll'rrrnp tt'r Lanc Wcave volumcs bclu'ccu ()rr rstlry. otl'rsrnp psir pcr 500 tl. of length 3c)4
l actors that Affect the Capacity and Level of Servicc
l. The Physical and operating width approaches. 2. The Physical and operating parking conditions. 3. Physical and operattng one way versus two way strocts 4 Environmental conditions - load factor 5. Environmental conditions - peak hour (r.
1 tt
Traffrc characteristics - turning movements Traffic characteristics - trucks and through buscs Traffic characteristics - local transit buscs
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