Irc 37 2001 Design Flexible Pavements

5/13/2018 Irc 37 2001 Design Flexible Pavements

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\\,._ IRC:37-2001

GUIDELINES FOR THE DESIGNOF

FLEXIBLE PAVEMENTS(Second Revision)

THE INDIAN ROADS CONGRESS2 0 0 1


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IRe: 37-2001First PublishedReprintedFirst RevisionReprintedReprintedSecond RevisionReprintedReprintedReprinted

IRC:37-2001GUIDELINES FOR THE DESIGN OF FLEXIBLE PAVEMENTS

Critical Locations, Relationship between Number . ..of Cumulative Standard Axles, Strain Valuesand Elastic Modulus of Materials- Modulus of Elastici ty of Subgrade, Sub-baseand Base Layers

- Substitution of Dense Bituminous Macadam 54(DBM)

Annexure-Z Equivalence Factors and Damaging Power of 55Different Axle Loads

September. 1970December, 1976December, 1984October, 1990 (IncorporatesAmendment No.1, September, 1988)April , 1995July, 2001March,2002July, 2004April,2005

CONTENTS

1.2.3.4.

Personnel of the Highways Specifications & StandardsCommitteeAbbreviationsIntroductionScopeRecommended Method of DesignPavement Thickness and Composition

5. Drainage Measures6. Design in Frost Affected Areas7. Worked Examples Illustrating the Design MethodANNEXURESAnnexure-I

(Rights of Publication and Translation are Reserved)

Page(i) to(v)(vi)

4519434748

51

53

Annexure-3 Preparation of Laboratory Test Specimens 57Annexure-a Special Points Relating to Design of Pavement 59

on Expansive SoilsAnnexure-5 Recommended Type and Thickness of 63

Bituminous Wearing Courses for FlexiblePavements under Different Situations

Annex~e-6 -Criteria for the Selection of Grade of Bitumen 65for Bituminous Courses

ReferencesPrinted at Aravali Printers & Publishers (P) Ltd., New Delhi-110020

(1000 copies)

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Director General (Road Dev.) & Add!'Secretary to the Govt, of India, Ministry ofRoad Transport & Highways, TransportBhavan, New Delhi-l 10001

IRC:37-2001PERSONNEL OF THE HIGHWAYS SPECIFICA nONS AND

STANDARDS COMMITTEE(As on 30.9.2000)

L Prafulla Kumar(Convenor)

s.c Sharma(Co-Convenor)

3, The Chief Engineer(R) S&R(Member-Secretary)

4, M.K. Agarwal

5, P. Balakrishnan

6, Dr, R.K. Bhandari

7, P,R. Dutta

Chief Engineer, Ministry of Road Transport& Highways, Transport Bhavan, New Delhi-110001(C.c. Bhattacharya), Ministry of RoadTransport & Highways, Transport Bhavan,New Delhi-l10001Members

Engineer-in-Chief (Retd.), House NoAO,Sector 16, Panchkula-134113Chief Engineer (Retd.), Highways & RuralWorks Department, No,7, Ashoka Avenue,Kodambakkam, Chennai-600024Head, International S&T Affairs Directorate,Council of Scientific & Industrial Research,Anusandhan Bhavan, 2, Rafi Marg, NewDelhi-l1000 1Chief Engineer (Mech.), Ministry of RoadTransport & Highways, Transport Bhavan,New Delhi-1 10001

ADG(R) being not in position, The meeting was presided by Shri PrafullaKumar , DG(RO) & Addl, Secretary to the Govt. of India, MORT&H

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IRC:37-20018. D.P. Gupta

9. Ram Babu Gupta

10. Dr. L.R. Kadiyali

11. lB. Mathur

12. H.L. Meena

13. S.S. Momin

14. Jagdish Panda

15. S.l. Patel

16. M.V. Patil

17. K.B. Rajoria

18. Dr. Gopal Ranjan

DG(RD) (Retd.), E-44, Greater Kailash Part-I Enclave, New Delhi-II 0048Chief Engineer-cum-Officer on Spl. Dutywith Public Works Minister, 9 HathoriMarket, Ajmer Road, Jaipur-302001Chief Executive, L.R. Kadiyali & Associates,C-6/7, Safdarjung Dev. Area, Opp. lIT MainGate, New Delhi-110016Chief Engineer, Ministry of Road Transport& Highways, Transport Bhavan, New Delhi-110001ChiefEngineer-cum-Addl. Secy. to the Govt.of Rajasthan, P.W.D., Jacob Road, Jaipur-302006Chief Engineer, Maharashtra State Road Dev.Corpn. Ltd., Nepean Sea Road, Murnbai-400036Engineer-in-Chief-cum-Secy. to the Govt. ofOrissa, Works Department, Bhubaneswar-751001Chief General Manager, National HighwaysAuthority of India, 1, Eastern Avenue,Maharani Bagh, New Delhi-110065Secretary (Roads), Maharashtra P.W.D.,Mantralaya, Mumbai-400032Engineer-in-Chief, Delhi P.W.D. (Retd.), C-II132, Moti Bagh, New Delhi-11 0031Director, College of Engg., Roorkee, 7thK.M. Roorkee-Hardwar Road, VardhmanPuram, Roorkee-247667

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I19. S.S. Rathore

20. K.K. Sarin

IrI21. Dr. S.M. Sarin

22. H.R. Sharma

23. Dr. C.K. Singh

24. Nirmal Jit Singh

25. Prabhash Singh

26. Dr. Geetam Tiwari

27. K.B. Uppal

28. V.C. Verma

IRC:37-2001Spi. Secretary & Chief Engineer (SP), R&B,Block No. 1411, Sardar Bhavan, Sachivalaya,Gandhinagar-38201ODG(RD) & AS, MOST (Retd.), S-108,Panchshila Park, New Delhi-l l0017Dy. Director, CRR! (Retd.), 2295, HudsonLines, G.T.B. Nagar, Delhi-110009Associate Director (Highways),Intercontinental Consultants & TechnocratsPvt. Ltd., A-II, Green Park, New Delhi-110016Engineer-in-Chief, PWD (Roads), Jharkhand,Project Building, H.E.C. Campus, RanchiChief Engineer (Pig.), Ministry of RoadTransport & Highways, Transport Bhavan,New Delhi-110001Chief Enginer, Zone-III, Delhi P.W.D., MSOBuilding, J.P. Estate, New Delhi-ll0002Transortation Res. & Injury PreventionProgramme, MS 808 Main Building, IndianInstitute of Technology, New Delhi-110016Director, AIMIL Ltd., Naimex House, A-S,Mohan Co-operative Indi . Estate, MathuraRoad, New Delhi-ll0044Executive Director, Oriental Structural Engrs.Ltd., 21, Commercial Complex, MalchaMarg, Diplomatic Enclave, New Delhi-110021

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IRC:37200129. P.D. Wani

30.

Member, Maharashtra Public ServiceCommission, 3'd Floor, Bank of IndiaBuilding, M.G. Road, Mumbai-400001

The Engineer-in-Chief (S.S. Juneja) H.P. Public Works Department,U.S. Club, Shimla-171001

31. The Chief Engineer(B) S&R (V. Velayutham), Ministry of Road Transport& Highways, Transport Bhavan, New Delhi-110001

32. The Principal Secy. to (H.P. Jamdar), R&B Department, Sardarthe Govt. of Gujarat Bhavan, Block No.J4, Sachivalaya,

Gandhinagar-38201033. The Engineer-in-Chief (V. Murahari Reddy), R&B Department,

A&EAP, Errum Manzil, Hyderabad-50008234. The Engineer-in-Chief (R.R. Sheoran), Haryana Public Works Deptt. ,

B&R, Sector 19-B, Chandigarh-1600 1935. The Member

36. The Director & Head

37. B.L. Tikoo

38. The Director (R&D),IOC

(RL. Koul) , National Highways Authorityof India , 1 ,Eastern Avenue, Maharani Bagh,New Delhi-l10065(S.K. Jain), Civil Engg. Department, Bureauof Indian Standards, Manak Bhavan, 9,Bahadur Shah Zafar Marg, New Delhi-110002Addl. Director General, Dte. General BorderRoads Seema Sadak Bhavan, Ring Road,Delhi Cantt., New Delhi-l10010(Dr. A.K. Bhatnagarj, Indian Oil CorporationLtd., R&D Centre, Sector 13, Faridabad-121007

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39. The Director

40. The Director Generalof Works

IRC:37-2001(V. Elango), Highways Research Station, P.B.No.2371, 76, Sardar Patel Road, Chennai -600025Engineer-in-Chiefs Branch, AHQ, KashmirHouse, Rajaji Marg, New Delhi-llOOll

Ex-Officio Members

Prafulla Kumar, Director General (RoadDev.) & Addl. Secretary to the Govt. ofIndia, Ministry of Road Transport &Highways, New Delhi-I 10001

41. The President, M. V. Patil, Secretary (Roads), MaharashtraIndian Roads Congress P.W.D., Mantralaya, Mumbai-400032

42. The D.G. (RD) &Addl, Secy.

43. The Secretary,Indian RoadsCongress

1. Prof. C.E.G. Justo

2. U. Mamtani

3. N.V. Merani

4. Prof. N. Ranganathan

G. Sharan, Chief Engineer, Ministry of RoadTransport & Highways, Transport Bhavan,New Delhi-I 10001

Corresponding MembersEmeritus Fellow, 334, 25th Cross, 14th Main,Banashankari 2nd Stage, Bangalore-560070Chief Engineer, MOST (Retd.), G-58, LajpatNagar-III, New Delhi-I 10024Principal Secretary, Maharashtra PWD(Retd.), A-47/I344, Adarsh Nagar, Worli,Mumbai-400025Head of Dept t. of Transpor tat ion PIg., SPA(Retd.), Consultant, 458/C/SFS, Sheikh SaraiI, New Delhi-ll0017

5 . Prof e . G . Swaminathan 'Badri', 6, Thiruvengandam Street , R.A.Puram, Chennai-600028(v)


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IRC:37-2001ABBREVIATIONS

1. AASHTO American Association of State Highway andTransportation Officials

2. BC Bituminous Concrete3. BUSG Built up Spray Grout4. BM Bituminous Macadam5. CBR California Bearing Ratio6. DBM Dense Bituminous Macadam7 . GB Granular Base8. GSB Granular Sub-Base9. IRC Indian Roads Congress10. MORT&H Ministry of Road Transport & Highways11. msa Million Standard Axles12. SDBC Semi-Dense Bituminous Concrete

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IRC:37-2001

GUIDELINES FOR THE DESIGN OF FLEXIBLE PAVEMENTS1. INTRODUCTION

The design of flexible pavement involves the interplay ofseveral variables, such as, the wheel loads, traffic, climate,terrain and sub-grade conditions. With a view to have a unifiedapproach for working out the design of flexible pavement in thecountry, the IRC first brought out guidelines in 1970. Thesewere based on California Bearing Ratio method. To handlelarge spectrum of axle load, these guidelines were revised in1984 following the equivalent axle load concept. In thisapproach, the pavement thickness was related to the cumulativenumber of standard axles to be carried out for different sub-grade strengths. These guidelines were based on semi-empiricalapproach based on a large extent on past experience andjudgement of highway agencies. Design curves were developedto cater upto 30 million standard axles.

With the rapid growth of traffic now, the pavements arerequired to be designed for heavy volume of traffic of the orderof 150 million standard axles. In the meanwhile, an in-house. software package was developed under MORT&H's ResearchScheme R-56. This enabled mathematical modelling of thepavement structure using multiple layer elastic theory. Withthis background and the feed back on the performance of theexisting designs, the Flexible Pavement Committee in 1997 setup a Sub-group consisting of the following personnel to reviewthe existing "Guidelines for Design of Flexible Pavements".This Sub-group developed the design charts and catalogue of


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IRC:37-2001 IRC:37-2001

S.C SharmaR.K. PandeyDr. L.R. KadiyaliDr. S.S. JainD.P. GuptaV.K. SoodDr. Sunil Bose

(Convenor) President, IRC(H.P. Jamdar)

Ex-Officio MembersD G (R D) & A dd l. S ecy ., M OR T& H(A.D. Narain)

Secretary,IRC(S.C. Sharma)

pavement designs for conditions prevailing in the country.Dr. M.P. Dhir

Hari Om Prakash SharmaR.S. Shukla

Corresponding MembersI.K. BhavsarDr. P.D. Marathe

Prof. S .P. JogThe Sub-group discussed revision of IRC:37 in a number

of meetings and finally on 10.8.98 submitted the revised draftto Flexible Pavement Committee (H-4). The draft was approvedby H-4 Committee (Personnel given below) in its meeting heldon 26.2.99 and the Convenor was authorised to incorporate thecomme~ts/suggestions made by the members and other expertsappropnately and send the final draft to Highways Specifications& Standards Committee for consideration and approval.

The draft was further vetted by an Expert Groupcomprising of Shri S.C. Sharma, Prof. B.B. Pandey and Dr.S.S. Jain and forwarded to newly constituted Flexible PavementCommittee.

D. BasuDr. A.K. BhatnagarDr. M.P. DhirD.P. GuptaDr. L.R. KadiyaliProf. C.E.G. JustoH.L. MeenaProf. B.B. Pandey

R.K. PandeyD. Sreerama MurthyProf. C.G. SwaminathanCol. V.K.P. SinghHargun DasCE (R) S&R MORT&H(C.C. Bhattacharya)

Dr. A.K. GuptaS.C. SharmaSpl. Secy. & Chief Engineer ...R&B Deptt., Gandhinagar,(S.S. Rathore)Dr . S.S. Jain

Convenor (upto 6.11.97)Convenor (w.e.f. 7.11.97)Co-Convenor

The newly constituted Flexible Pavement Committee(Personnel given below) in its meeting held on 23.9.2~00discussed and approved the revised draft of IRC:37 for placmgbefore the Highways Specifications & Standards (HSS)Committee for approval.

Member-SecretaryMembers

S.C SharmaSpl, Secy. & Chief Engr.R&B Deptt., Gandhinagar(S.S. Rathore)Dr. S.S. Jain

ConvenorCo-convenor

Member-SecretaryProf. C.G. SwaminathanDr. M.S. SrinivasanProf. C.E.G. JustoR.K. JainB.K. DarnB.R. TyagiI.C. GoelDr. L.R. KadiyaliProf. B.B. PandeyDr. M.P. DhirD.P. Gupta

Engineer-in-Chief, Army HQ(Maj. Gen. CT. Chari )Chief Engineer(R) S&R,MORT&H

(Indu Prakash)Head, Flexible PavementDivision, CRR! (I.R. Arya)Rep. ofDGBR (A.R. Aiyengar)Engineer-in-Chief, UP PWD(Ravinder Kumar)

Members

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IRC:37-200 I IRC:37-200JEx-Officio Members

President, IRCIM.V. Patil) DG (RD )&Add l . Secy. MORT& H(Prafulla Kumar)

Secretary,IRC(G. Sharan)

for Road and Bridge Works, Ministry of Road Transport andHighways.

2.3. These guidelines apply to new pavements.

Corresponding Members2.4. For design of strengthening measures or overlays

for existing pavements, the design procedure described inIRC: 81 "Tentative Guidelines for Strengthening of FlexibleRoad Pavements Using Benkelman Beam Deflection Technique"shall apply.

Sukomal Chakraborty Smt. A.P. JoshiR.S. Shukla

The HSS Committee in its meeting held on 30.9.2000after detailed discussion approved the revised draft IRC:37 andauthorised the Convenor, Flexible Pavement Committee tomodify the same in light of the comments of members andsubmit to Convenor, HSS Committee for its approval. The draftof revised guidelines as modified by the Convenor, HSSCommittee was approved by the Executive Committee in itsmeeting held at New Delhi on 5.10.2000 and by the Council inits meeting held at Kolkata on 4.11.2000. The draft as modifiedin light of comments of members of the Council was approvedby the Convenor, HSS Committee on 12.2.2001 for printing.

2.5. The guidelines may require revision from time totime in the light of future experience and developments in thefield. Towards this end, it is suggested that all the organisationsintending to use the guidelines, should keep a detailed recordof year of construction, subgrade CBR, soil characteristics,pavement composition and specifications, traffic, pavementperformance, overlay history, climatic conditions, etc. andprovide feedback to the Indian Roads Congress.

3. RECOMMENDED METHOD OF DESIGN

2. SCOPE 3.1. General2.1. These guidelines will apply to design of flexiblepavements for Expressways, National Highways, State

Highways, Major District Roads and other categories of roadspredominantly carryingmotorised vehicles.

The pavement designs given in the previous editionIRC:37-1984 were applicable to design traffic upto 30 millionstandard axles (msa). With the increasing traffic and incidenceof overloading, arterial roads need to be designed for traffic fargreater than 30 msa. As empirical methods have limitationsregarding their applicability and extrapolation, the analyticalmethod of design has been used to reanalyse the existingdesigns and develop a new set of designs for design traffic upto150 msa making use of the results of pavement research work

2.2. For the purpose of the guidelines, flexible pavementsare considered to include the pavements which have bituminoussurfacing and granular base and sub-base courses conformingto IRC Standards or to Sections 500 and 400 of the Specifications

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IRC:37-2001done in the country and experience gained over the years on theperformance of the existing designs.

3.2. Design Approach and Criteria

IRC:37-2001Macadam (DBM) layer with 60170 bitumen has been used inthe analysis. The relationships used for (i) allowable verticalsubgrade strain; and (ii) allowable tensile strain at the bottom'of the DBM layer along with elastic moduli of differentpavement materials and the relationships for assessing theelastic moduli of subgrade, granular sub-base and base layersare given in Annexure-I .

3.2.1. The flexible pavement has been modelled as a threelayer structure and stresses and strains at critical locations(Annexure-L) have been computed using the linear elasticmodel FPAVE developed under the MORT&H Research SchemeR-56 "Analytical Design of Flexible Pavements'".

7

(i) Vertical compressive strain at the top of the subgrade. If thestrain is excessive, the subgrade will deform resulting inpermanent deformation at the pavement surface during thedesign life.

3.2.3. Based on the performance of existing designs andusing analytical 'approach, simple design charts (Figs. 1 and 2)and a catalogue of pavement designs (Plates 1 and 2) have beenadded for use of field Engineers. The pavement designs aregiven for subgrade CBR values ranging from 2 per cent to 10per cent and design traffic ranging from 1 msa to 150 msa foran average annual pavement temperature of 35C. The layerthicknesses obtained from the analysis have been slightlymodified to adapt the designs to stage construction. Using thefollowing simple input parameters, appropriate designs couldbe chosen for the given traffic and soil strength :

3.2.2. To give proper consideration to the aspect ofperformance, the following three types of pavement distressresulting from repeated application of traffic loads areconsidered:

(ii) Horizontal tensile strain at the bottom of the bituminouslayer. Large tensile strains cause fracture of the bituminouslayer during the design life.

( ii i) Pavement deformation within the bituminous layer.

(i) Design traffic in terms of cumulative number of standardaxles; and

While the permanent deformation within the bituminouslayer can be controlled by meeting the mix design requirementsas per the MORT &H Specification", thicknesses of granularand bituminous layers are selected using the analytical designapproach so that strains at the critical points are within theallowable limits.

(i i) CBR value of subgrade

The procedure for estimating design traffic and assessingthe CBR value of the subgrade soil is described in paragraphs3.3 and 3.4 respectively.

3.3. Traffic3.3.1. General

For calculating tensile strains at the bottom of thebituminous layer, the Elastic Modulus of Dense Bituminous 3.3.1.1. The recommended method considers traffic interms of the cumulative number of standard axles (8160 kg) to

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IRC:37-2001

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IRC:37-2001IRC:3 7-200 Ibe carried 1 : J y the pavement during the design life. For estimatingdesign traffic, the following information is needed :

(ii) by establishing econometric models, as per the procedureoutlined in IRC: 108 "Guidelines for Traffic Prediction onRural Highways".

(i) Initial traffic after construction in terms of number ofcommercial vehicles per day (CVPD)

3.3.2.2. If adequate data is not available, it is recommendedthat an average annual growth rate of 7.5 per cent may beadopted.

( ii) Traffic growth rate during the design life in percentage

(v) Distribution of commercial traffic over the carriageway.

3.3.3. Design life3.3.3.1. For the design of pavement, the design life is

defined in terms of the cumulative number of standard axlesthat can be carried before strengthening of the pavement isnecessary.

(i ii) Design life in number of years(iv) Vehicle damage factor (VDF)

3.3.1.2. For the purpose of structural design, only thenumber of commercial vehicles of gross vehicle weight of threetonnes or more and their axle-loading is considered.

3.3.1.3. To obtain a realistic estimate of design traffic, dueconsideration should be given to the existing traffic or thatanticipated based on possible changes in the road network andland use of the area served, the probable growth of traffic anddesign life.

3.3.3.2. It is recommended that pavements for NationalHighways and State Highways should be designed for a life of15 years. Expressways and urban roads may be designed for alonger life of 20 years. For other categories of roads, a designlife of 10 to 15 years may be adopted.

3.3.3.3. Very often it is not possible to provide the fullthickness of pavement right at the time of Init ial construction.Stage construction techniques should be resorted to in suchcases.

Estimate of the initial daily average traffic flow for anyroad should normally be based on atleast 7 days, 24 hourclassified traffic counts. In cases of new roads, traffic estimatescan be made on the basis of potential land use and traffic onexisting routes in the area.

3.3.2. Traffic growth rate

3.3.4. Vehicle damage factor3.3.4.1. The vehicle damage factor (VDF) is a multiplier

to convert the number of commercial vehicles of different axleloads and axle configuration to the number of standard axleload repetitions. It is defined as equivalent number of standardaxles per commercial vehicle. The VDF varies with the vehicleaxle configuration, axle loading, terrain, type of road and fromregion to region. The VDF is arrived at from axle load surveys

II3.3.2.1. Traffic growth rates should be estimated:

(i) by studying the past trends of traff ic growth, and10


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IRC:37-2001 IRC:37-2001Distribution of commercial traffic over the3.3.5. carriageway3.3.5.1. A realistic assessment of. distribution o.f

commercial traffic by direction and by lane IS necessary as Itdirectly affects the total equivalent standard axle loadapplications used in the design. In the abs~nce of adequate andconclusive data for Indian conditions,. it I.Srecommended thatfor the time being the following distnbutIon may be assum~dfor design until more reliable data on place~ent ~f commercialvehicles on the carriageway lanes are available

on typical road sections so as to cover various influencingfactors, such as traffic mix, mode of transportation, commoditiescarried, time of the year, terrain, road conditions and degree ofenforcement.

3.3.4.2. The axle load equivalency factors recommendedin the AASHTO guide are given in Annexure-2. They are usedfor converting different axle load repetitions into equivalentstandard axle load repetitions.

3.3.4.3. For designing a new pavement, the VDF shouldbe arrived at carefully by carrying out specific axle loadsurveys on the existing roads. Some surveys have been carriedout in the country on National Highways, State Highways andMajor District Roads which reveal excessive overloading ofcommercial vehicles. Therefore, it is recommended that thedesigner should take the realistic values ofVDF after conductingthe axle load survey, particularly in the case of major projects.On some sections, there may be significant difference in axleloading in two directions of traffic. In such situations, the VDFshould be evaluated direction wise to determine the laneswhich are heavily loaded for the purpose of design.

(i) Single-lane roadsTraffic tends to be more channelised on single-lane. roadsthan two-lane roads and to allow for this concentratlOn ofwheel load repetit ions, the design should ~e b~sed on totalnumber of commercial vehicles in both dlrectlOns.

( ii) Two-lane single carriageway roadsThe design should be based on 75 per .cent. of the totalnumber of commercial vehicles in both dlrectlOns.

3.3.4.4. Where sufficient information on axle loads is notavailable and the project size does not warrant conducting anaxle load survey, the indicative values ofvehic1e damage factoras given in Table 1 may be used.

( ii i) Four-lane single carriageway roadsThe design should be based on 40 per .cent. of the totalnumber of commercial vehicles in both direcuons.

Initial traffic volume in terms of numberof commercial vehicles per day

TerrainRolling/Plain Hilly

(iv) Dual carriageway roadsThe design of dual two-lane carriageway roads. shoul~ beb don 75 per cent of the number of commercial vehiclesi:s :ach direction. For dual three-lane carriagew.ay and dualfour-lane carriageway, the distribution factor will be 60 percent and 45 per cent respectively.

TABLE 1. INDICATIVE VDF VALUES

0-150150-1500More than 1500

1.53.54.5

0.51.52.5

3.3.5.2. The traffic in each direction may be assumed t.obe half of the sum in both directions when the latter only IS

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IRC:37-2001known. Where significant difference between the two streamscan occur, condition in the more heavily trafficked lane shouldbe considered for design.

IRC:37-2001The traffic in the year of completion is estimated using

the following formula :A = P(1 + r}"

Where the distribution of traffic between the carriagwaylanes and axle loads spectrum for the carriageway lanes areavailable, the design should be based on the traffic in the mosthea~ily trafficked lane and the same design will normally beapplied for the whole carriageway width.

where,P =Number of commercial vehicles as per last count .x = Number of years between the last count and the year of

completion of construction.3.3.6. Computation of design traffic 3.4. Subgrade3.3.6.1. The design traffic is considered in terms of the

cum~lative number of standard axles (in the lane carryingmaximum traffic) to be carried during the design life of theroad. This can be computed using the following equation :

3.4.1. The subgrade whether in cut or fill should be wellcompacted to utilise its full strength and to economise therebyon the overall thickness of pavement required. For Expressways,National Highways, State Highways and Major District Roads,heavy compaction is recommended. Most of the specificationsprescribe use of selected material and stiffer standards ofcompaction in the sub grade (top 500 mm portion of theroadway). The current MORT&H Specification for Road &Bridge Works (Third Revision 1995) recommend that thesubgrade shall be compacted to 97 per cent of dry densityachieved with heavy compaction (modified proctor density) asper 1S:2720 (Part 8). This density requirement is recommendedfor subgrade compaction for Expressways, National Highways,State Highways, Major District Roads and other heavilytrafficked roads. Inother cases the subgrade should be compactedto atleast 97 per cent of the standard proctor density conformingto 1S:2720 (Part 7). These requirements should be strictlyenforced. 1RC:36 "Recommended Practice for the Constructionof Earth Embankments for Road Works" should be followedfor guidance during planning and execution of work.

365x[(I+r)"-l}N= xAxDxFrwhere,

N =The cumulative number of standard axles to be catered forin the design in terms of msa.A =Initial traffic in the year of completion of construction in

terms of the number of commercial vehicles per day.D =Lan~ distribution factor (as explained in para 3.3.5)F =Vehicle damage factorn = Design life in yearsr =Annual growth rate of commercial vehicles (for 7.5 per centannual growth rate, r = 0.075)

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IRC:37-20013.4.2. For high category roads, like, Expressways, National

Highways and State Highways, the material used for subgradeconstruction should have the dry density of not less than 1.75gm/cc.

IRC:37-.2001should be compacted to a dry density corresponding to theminimum state of compaction likely to be achieved in practicehaving regard to the compaction equipment used and thecompaction limits specified.

3.4.3. For design, the subgrade strength is assessed interms of the CBR of the subgrade soil in both fill and cutsections at themost critical moisture conditions likely to occurin-situ.

3.4.5.3. The moisture condition of the subgrade which thetest sample is expected to simulate is governed by localenvironmental factors, such as, the water table, precipitation,soil permeabili ty, drainage conditions and the extent to whichthe pavement is waterproof. Thin surfacings do not always sealthe pavement effectively against ingress of water. Further, theberms and verges are usually unsurfaced, and if not kept inwell-maintained state to the requisite cross-fall, will enablesurface water to percolate into the subgrade from near theedges of the pavement, leading to weak subgrade conditions.

3.4.4. For determining the CBR value, the standard testprocedure should be strictly adhered to. This is described inIS:2720 (Part 16) "Methods of Test for Soils; LaboratoryDetermination of CBR". The test must always be performed onremoulded samples of soils in the laboratory. Wherever possiblethe test specimens should be prepared by Static Compactionbut if not so possible dynamic method may be used as analternative. Both procedures are described in brief in Annexure-3. In-situ tests are not recommended for design purposes as itis not possible to satisfactorily simulate the critical conditionsof dry density and moisture content in the' field.

3.4.5. Selection of dry density and moisture contentfor test specimen

Hence, it is recommended that as a general practice, thedesign for new construction should be based on the strength ofthe samples prepared at the values of prescribed dry densityand moisture content obtained in accordance with IS:2720 (Part8) or (Part 7) as the case may be and soaked in water for aperiod of four days prior to testing. Use of expansive clays isnot allowed for subgrade construction particularly for heavilytrafficked roads. As far as possible, a non-expansive soil shouldbe used for the subgrade. Where use of expansive clays isunavoidable, the compaction requirements. and additionalmeasures as discussed in Annexure-A should be followed.3.4.5.1. For a given soil, the CBR value and consequentlythe design, will depend largely on the density and moisture

content of the test sample. Therefore, the test conditions shouldreproduce as closely as possible the weakest conditions likelyto occur under the road after construction.

3.4.5.4. However, it should be realised that soaking forfour days may be an unrealistically severe moisture conditionin certain cases, where the climate is arid throughout the year,i.e., the annual rainfall is of the order of 500 mm or less and3.4.5.2. The samples of soil collected from selected borrow

pits for fill sections or from subgrade level at cut sections16 17


15/39

IRC:37-2001~he w~t~r table is too deep to affect the subgrade adversely. ItIS anticipated that in this situation the most severe moisturecondition in the field will be far below that of the sample at theend of four days soaking, resulting in unduly conservativedesigns if soaking procedure is adopted. In such cases the. ,specimens for finding the CBR value may be prepared at the~atural. moisture content of the soil at subgrade depthimmediately after recession of the monsoon.

3.4".6. Use of test results for design and the minimumnumber of tests required

3.4.6.1. The design should be based on the CBR value ofthe wea~est soil type proposed to be used for sub gradeconstruction or encountered extensively at subgrade level overa given sect~on of the road, as revealed by the soil surveys.Pavement thickness on new roads may be modified at intervalsas dictated by the soil changes but generally it will be foundinexpedient to do so frequently from practical considerations.

3.4.6.2. It is possible that in certain soil types or underabnormal conditions the measured CBR values may appeardoubtful and not truly representative of the strength of soil. Amore complete study of the soil may be warranted in such casesto arrive at a more reliable design.

3.4.6.3. The design evolved should be revised duringconstruction phase if found necessary on account of the fieldcompaction being lower than that considered in the initialdesign. In addition, the alternative of retaining local areas ofsoft soil or soil not meeting prescribed compaction level shouldalso be considered.

1 8

IRC:37-20013.4.6.4. As the reproducibility of the CBR results is

dependent on a number of factors, wide variations in values canbe expected. Therefore, atleast three samples should be testedon each type of soil at the same density and moisture content.This will enable a reliable average value to be obtained in mostcases. To weed out erratic results, permissible maximumvariation within the CBR values from the three specimens isindicated in Table 2.

T A B LE 2 . P ER M IS SI BL EV A R IA T IO NI N C B R V A L UECBR (per cent) Maximum variation in CBR value55-1011-3031 and above

12 3 5

Where variation is more than the above, the design CBRvalue should be the average of test results from atleast sixsamples and not three.

4. PAVEM ENT TH ICKNESS AND COM POSITIO N4.1. Pavement Thickness Design ChartsFor the design of pavements to carry traffic in the rangeof 1 to 10 msa, the Pavement Thickness Chart is given in Fig.

1 and for traffic in the range of 10-150 msa, the PavementThickness Design Chart is given in Fig. 2. The design curvesrelate pavement thickness to the cumulative number of standardaxles to be carried over the design life for CBR values ofsubgrade ranging from 2 per cent to 10 per cent. The thicknessdeduced from Fig. 1 or Fig. 2 for the given CBR value and

19


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IRC:37-2001IRC:37-200 1design traffic is the total pavement thickness to be provided andconsists of granular sub-base, granular base and bituminoussurfacing. The requirements for the component layers are givenin paragraph 4.2. Based on these, the recommended designsgiving minimum thickness and compositions of pavement layersfor new constructions are given in the Pavement DesignCatalogue, Plates 1 and 2. The design procedure is illustratedwith examples in paragraph 7.

PAVEMENT DESIGN CATALOGUEP LA TE 1 _ R EC OM M EN DED D ES IG NS FO R T RA FFIC R A NG E 1 -1 0 m sa

CBR2%Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Granular(msa) Thickness Wearing Binder Base Sub-base(mm) Course Course (mm) (mm)(mm) (mm)I 660 20 PC 225 4352 715 20 PC 50 BM 225 4403 750 20 PC 60 BM 250 4405 795 25 SDBC 70 DBM 250 45010 850 40 BC 100 DBM 250 460

4.2. Pavement Composition4.2.1. Sub-base course4.2.1.1. Sub-base materials comprise natural sand moorum ,

gravel, laterite, kankar, brick metal, crushed stone, crushedslag, crushed concrete or combinations thereof meeting theprescribed grading and physical requirements. When the sub-base material consists of combination of materials, mixing shallbe done mechanically either using a.suitable mixer or adoptingmix-in-place method.

EE

Granular sub-base materials conforming to Clause 401 ofMORT&H Specifications for Road and Bridge Works arerecommended for use. These specifications suggest threegradings each for close and coarse graded granular sub-basematerials and specify that the materials passing 425 micronsieve when tested in accordance with IS:2720 (Part 5) shouldhave liquid limit and plasticity index of not more than 25 and6 respectively. These requirements and the specified grain sizedistribution of the sub-base material should be strictly enforcedin order to meet stability and drainage requirements of thegranular sub-base layer.

I

(msa)

e a GSB IIlIDGB ~ DBM ~ BM IIBC SDBC m PCContd.

20 21


17/39

IRC:37-2001PAVEMENT DESIGN CATALOGUE

P LA TE 1 - R EC OM M EN D ED D ES IG N S FO R T RA FFIC R AN G E 1 -1 0 m saCBR3% -,_ ...

Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Granular(msa) Thickness Wearing Binder Base Sub-base

(mrn) Course Course (mrn) (mrn)(mrn) (mrn)

1 550 20 PC 225 4352 610 20 PC 50 BM 225 3353 645 20 PC 60 BM 250 3355 690 25 SDBC 60 DBM 250 33510 760 40 BC 90 DBM 250 380

8'00

T R A FF IC (msa)~ GSa I I I I D GB Ia OBM ~. BM l 1 l i BC SOBC Ir]J PC

Contd.

EE

1 1 ' 11 1 ' 1 200" "zx ::U:J:~

22

lRC:37-2001PAVEMENT DESIGN CATALOGUE

P LA TE 1 - R EC OM M EN DE D D ES IG NS FO R T RA FFIC R AN G E 1 -1 0 m saCBR4%

Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Granular(msa) Thickness Wearing Binder Base Sub-base(mrn) Course Course (mrn) (mm)

(mrn) (mrn)1 480 20 PC 225 2552 540 20 PC 50 BM 225 265-.3 580 20 PC 50 BM 250 2805 620 25 SDBC 60 DBM 250 28510 700 40 BC 80 DBM 250 330

800~-------------------------------'EE~ 600t=inoQ.Zou400of1 1 ' 11 1 ' 1

" "Zx ::Ul:,_TRAFFIC (msa )

~ GSJ I i l i l l GB E 3 OBM ~ BM I I I B BC SOBe ~ PCContd.

23


18/39

IRC:37-200lPAVEMENT DESIGN CATALOGUE

P LA TE 1 - R EC OM M EN DE D D ES IG NS FO R T RA FFIC R AN GE 1 -1 0 m sa-,7-2oUl

PAVEMENT DESIGN CATALOGUEP LA TE 1 - R EC OM M EN DE D D ES IG NS FO R T RA FFIC R A NG E 1 -1 0 m sa

CBR5%Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Granular(msa) Thickness Wearing Binder Base Sub-base(mm) Course Course (mm) (mm)

(mm) (mm)1 430 20 PC. 225 2052 490 20 PC 50 BM 225 2153 530 20 PC 50 BM 250 2305 580 25 SDBC 55 DBM 250 25010 660 40 BC 70 DBM 250 300

CBR6%Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Granular(msa) Thickness Wearing Binder Base Sub-base

(mm) Course Course (mm) (mm)(mm) (mm)


zoi=VIoQ.2:oV01~WZl I C :V.X~ OL-~~~--~~L-~~~--~~~~~~~

E 70 0 CBR 5 .,.Ez 6000t=iii0Q. 4002:0V01VIVI 2 00~l I C :Vl:~ 0 2

TRAFFIC (rns c )

~GSB DIIDGS laOBM ~ BM IIIBe _SOBe r : 3 l PCContd.

24

EE C . B R 6 -t,

~GSB mmGB E:30BM ~BM IIBe .SDBe ~PCTRAFFIC (msa)

Contd.


19/39


PLATE 1 - RECOM MENDED DESIGNS FOR TRAFFIC RANGE 1-10 m saIRC:37-2001

PAVEMENT DESIGN CATALOGUEPLATE 1 - RECOM MENDED DESIGNS FOR TRAFFIC RANGE 1-10 m sa

CBR 7%Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Granular(msa) Thickness Wearing Binder Base Sub-base(mm) Course Course (mm) (mm)(mm) (mm)1 375 20 PC 225 1502 425 20 PC 50 BM 225 1503 460 20 PC 50 BM 250 1605 505 25 SDBC 50 DBM 250 18010 580 40 BC 60 DBM 250 230

CBR 8%Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Granular(msa) Thickness Wearing Binder Base Sub-base

(mm) Course Course (mm) (mm)(mm) (mm)


, . . . .E 700r-----------------------------------~Ez 600Qt:If)~~ 400oI.J' "

700E eS R 7 "I,EzQ~in0a.~0u'"IIIf) 200UJZ: : ICI.JX. . . 0

TR AFF IC (msa)

e S R 8 'I,

If)If) 200UJZ: : ICU:x :._

_ \

10TRAFFIC (msa)

~ GSB r n m GB e a DBM ~ BM 1 1 m Be SDBC ~pe

26Contd.

Contd.~ GSB m m GB 53 DBM ~ BM lIII BC SDBC ~ PC

27


20/39


PLATE 1- RECOMMENDED DESIGNS FOR TRAFFIC RANGE 1-10 m saCBR 9% & 10%

Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Granular(msa) Thickness Wearing Binder Base Sub-base

(rom) Course Course (rom) (rom)(rom) (mm)

1 375 ' 20 PC 225 1502 425 20 PC 50 BM 225 1503 450 20 PC 50 BM 250 1505 475 25 SDBC 50 DBM 250 15010 540 40 BC 50 DBM 250 200

EE; 600o~e noQ.~ 4ou. .e n, I n 200z~u:z :~ OL-_LL?a__J~~--~~--~~--~~~~

eBR 9 'J , & 10 'J .

TR AFFle (msa)

f i ! Z J GSa D I I D GB IOBM ~ BM I I I Be SOBC ~ PC

28

IRC:37-200 IPAVEMENT DESIGN CATALOGUE

PLATE 2 - RECOMMENDED DESIGNS FOR TRAFFIC RANGE 10-150 m saCBR 2%

Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Base .(msa) Thickness BC DBM & Sub-base

(rom) (rom) (mm) (rom)10 850 40 10020 880 40 r 130 .30 900 40 150 Base = 250.5.0 925 40 175100 955 50 195 Sub-base = 460150 975 50 215

eBR 2 '1.

eezQt-v :;0Q~0v 400. .IIIIIIWz 200>t:Ui:t- o 10 50

TR AFFIC (msa)

~ GSB D I l l GB iii OBM l1li BeContd.

29

...


21/39


PL AT E 2 - R EC OM M EN DE D D ES IG NS FO R T RA FFIC R AN GE 10-150 m saCBR3%

Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Base(msa) Thickness BC DBM & Sub-base

(mm) (mm) (mm) (mm)10 760 40 9020 790 40 12030 810 40 140 Base = 25050 830 40 160100 860 50 180 Sub-base = 380150 890 50 210

IRC:37-20i)jPAVEMENT DESIGN CATALOGUE

P LA TE 2 - R EC OM M EN DE D D ES IG NS FO R T RA FFIC R AN GE 10-150 m saCBR 4%

Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Base(msa) Thickness BC DBM & Sub-base(mm) (mm) (mm) (mm)

10 700 40 8020 730 40 11030 750 40 130 Base = 25050 780 40 160100 800 50 170 Sub-base = 330150 820 50 190

9 0 0 ' - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - _ ,B R 4/.8

EEzo 6~IfI~~o 40 , . >05~WZ:. cv:J:. . . . .

TRAFF IC (mso)

m GSB m m GB iiiOBM III BeContd.

31

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


22/39

IRC:37-2001 IRC:37-2001PAVEMENT DESIGN CATALOGUE

PLATE 2 - RECOM MENDED DESIGNS FOR TRAFFIC RANGE 1 0-1 50 msaPAVEMENT DESIGN CATALOGUE

PLATE 2 - RECOM M END ED D ES IGNS FOR TRAFFIC RANGE 1 0-150 m saCBR5%



EEz0i=III0C L2:0u.,IIIIII" "lCV:r :. . . .

0

CBR6%Cumulative Total PAVEMENT COMPOSITIONTraffic Pavement Bituminous Surfacing Granular Base(msa) Thickness BC DBM & Sub-base


CBR 5 .,.

TRAFFIC ( m s o )

EE CBR 6 .,.zQ. . . .IIIoC L:Eou.,IIIIIIWZx:UJ:. . . .

TRAFFIC (msa)

~ GSB l1li GB m Gsa I I l D GB iii OBM IIBC! ! ! I OBM l1li BeContd. Contd.

32 33


23/39


PLATE 2 - RECOMMENDED DESIGNS FOR TRAFFIC RANGE 10-150 rnsaCBR 7%



E 8 0 0 ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~E eBR 7 00zQl-I/)oQ~oVoi lI/)I/)U JZx:v:rI-

TRAFFIC (rns c )m GSB D U D GB IIDBM l1li Be

34

IRL:37-2001PAVEMENT DESIGN CATALOGUE

PLATE 2 - RECOMMENDED DESIGNS FOR TRAFFIC RANGE 10-150 m saCBR 8%



Contd.

Ee~l-I/)oQ.~8 4oi lI/)I/)UJZx:v:rI-

c B R 8 00

( msa)

fa GSa o m GB IIDBM l1li Be

35

Contd.


24/39


PLATE 2 - RECO M MEND ED D ESIG NS FO R TRA FFIC RA NGE 10-150 m saCBR9%


10 540 40 5020 570 40 8030 585 40 95 Base = 25050 605 40 115100 635 50 135 Sub-base = 200150 655 50 155

EE 700 CBR 9 'I,z0t:III'oQ.

,~ ~0v. .IIIIII1 1Z: r : :vx~ 0 3

TRAFFIC ( msa)~ GSB m I l GB ~ DBM II I B e

Contd.

36


PLATE 2 - RECO M MENDED D ES IGN S FOR TRA FFIC RANG E to - ISO m saCBR 10%


10 540 40 5020 565 40 7530 580 40 90 Base = 25050 600 40 110100 630 50 130 Sub-base = 200150 650 50 150

. . .EE 700~--------------~--------------------~. . . . C B R 10'/,zoi=iiioQ.~ 4v. .IIIIIIWZ: r : :vx~

TRAFFIC. (msQ)

~ GSa IIIIIG8 !!8M II I BCContd.

37


25/39

lRC:37-2001The sub-base material should have minimum CBR of 20

per cent for cumulative traffic upto 2 msa and 30 p~r cent fortraffic exceeding 2 msa. It should be ensured prior to actualexecution that the material to be used in sub-base satisfies theCBR and other prescribed physical requirements. The materialshould be tested for CBR at the dry density and moisturecontent expected in the field. Where soaking conditions applyfor design, the minimum strength of the sub-base materialshould be determined after soaking the test specimen in waterfor four days.

4.2.l.2. Where the granular sub-base material conformingto the above specifications is not available economically, othergranular sub-bases, like, Water Bound or Wet Mix Macadamconforming to MORT&H Specifications are recommended.

4.2.1.3. From drainage considerations the granular sub-base should be extended over the entire formation width in casethe subgrade soil is of relatively low permeability. The thicknessof sub-base in the extended portions should not be less than theprescribed minimum as given in para 4.2.1.4.

4.2.].4. The thickness of sub-base should not be less than150 mm for design traffic less than 10 msa and 200 mm fordesign traffic of 10 msa and abcve.

4.2.1.5. Preferably the subgrade soil should Dave a CBRof 2 per cent. Where the CBR value of the subgrade is less than2 per cent, the design should be based on subgrade CBR valueof 2 per cent and a capping layer of 150 mm thickness ofmaterial with a minimum CBR of 10 per cent shall be providedin addition to the sub-base.

38

IRC:37-20014.2.1.6. Where stage construction is adopted for pavements,

the thickness of sub-base shall be provided for ultimate pavementsection for the full design life.

4.2.1.7. In the areas affected by frost, care should betaken to avoid using frost susceptible materials in the sub-base.

4.2.2. Base course4.2.2.1. Unbound granular bases which compnse

conventional Water Bound Macadam (WBM), Wet MixMacadam (WMM) or other equivalent granular constructionconforming to IRC/MOR T&H Specifications shall beadopted.

4.2.2.2. Materials for use in the base course must satisfythe grading and physical requirements prescribed in the IRC/MORT&H Specifications. The recommended minimumthickness of granular base is 225 mm for traffic upto 2 msa and250 mm for traffic exceeding 2 msa.

4.2.2.3. For heavily trafficked roads, use of WMM baselaid by paver finisher or motor grader is recommended.

4.2.2.4. Where WBM construction is adopted in the basecourse for roads carrying traffic more than 10 msa, the thicknessofWBM base-shall be increased from 250 mm to 300 mm (i.e.,4 layers of WBM grades II and III each of 75 mm compactedthickness) for ease of construction with corresponding reductionin the sub-base thickness keeping the overall pavement thicknessunchanged as deduced from the design chart.

39


26/39

IRC:37-20014.2.3. Bituminous surfacing IRC:37-2001

thick Bituminous Macadam (BM) layer. Where this is done thethickness of the DBM layer will be suitably reduced. Forpractical purposes 10 mm BM can be taken as equivalent to 7mm DBM for modifying the thickness of DBM layer.

4.2.3.1. The bituminous surfacing shall consist of either awearing course or a binder course with a wearing coursedepending upon the traffic to be carried. The most common~yused wearing courses are surface dressing, open-graded premixcarpet, mix seal surfacing, semi-dense bituminous concrete andbituminous concrete. For binder courses, the MORT&HSpecification prescribes Bituminous Macadam and ~enseBituminous Macadam. Bituminous Macadam has low bmdercontent and high voids and is thus not impervious to water.Further the effect of high voids is reduced stiffness and increasedstress concentrations. From fatigue considerations, thedeterimental effect of voids is more apparent at low temperatures.On the other hand, during prolonged hot spells the averagepavement temperatures are very high and consequently such amix will operate over a very low stiffness range. Hence, the useof bituminous macadam binder course to IRCIMORT&HSpecifications may desirably be restricted only to roads designedto carry traffic less than 5 msa. Dense Bituminous Macadambinder course is recommended for roads designed to carry morethan 5 msa.

4.2.3.4. Choice of the appropriate type of bituminouswearing course will depend on several factors, like, designtraffic over the service life, the type of baselbinder courseprovided, whether the pavement is to be built up in. stages,rainfall and other related factors. The recommended types andthic1&esses of wearing courses for traffic from 10 msa to 150msa are given in Plate 2 and for traffic less than 10 msa in Plate1, which may be read in conjunction with Annexure-5 and maybe modified if the environmental conditions and experience sojustify.

4.2.3.2. Recommended surfacing materials and thicknessesin terms of the cumulative standard axles to be carried duringthe design life are given in Plates 1 and 2. The suggestedsurfacings are a desirable minimum from functional andstructural requirements.

4.2.3.5. The grade of bitumen will be selected keeping inview the traffic, rainfall and other environmental conditions.The selection criteria for the grade of bitumen to be used forbituminous courses are given in Annexure-6. Use of highperformance mixes/modified binders are recommended inheavily trafficked situations.

4.2.3.3. However, in case the granular base is manuallylaid or if recommended by the Engineer, the Dense BituminousMacadam (DBM) binder course may be preceeded by a 75 mm

4.2.3.6. For areas with heavy snow precipitation wheremechanised snow clearance operations may be undertaken aswell as at locations, like, bus stops and roundabouts,consideration ought to be given to the provision of bituminousconcrete in single or multiple courses so as to render thesurface more stable and waterproof. Mastic asphalt may beused at bus-stops and intersections.

4140


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IRC:37-20014.2.3.7. Where the wearing surface adopted is open graded

premix carper of thickness upto 25 mm, the thickness ofsurfacing should not be counted towards the total thickness ofthe pavement as such surfacing will be purely for wearing andwill not add to the structural capacity of the pavement.

IRC:37-20014.3.3. For intermediate traffic ranges, the pavement layer

thicknesses will be interpolated linearly.

4.3. Pavement Design Catalogue

4.3.4. For traffic exceeding 150 msa, the pavement designappropriate to 150 msa may be chosen and further strengtheningcarried out to extend the life at the appropriate time based onpavement deflection measurements as per IRC:81.

5. DRAINAGE MEASURES4.3.1. Based on the results of analysis of pavementstructures, practical requirements and specifications spelt out inparagraph 4.2, the recommended designs for traffic range 1msa to 10 msa are given in Plate 1 and for traffic range 10 msato 150 msa are given in Plate 2. In some cases, the totalpavement thickness given in the recommended designs is slightlymore than the thickness obtained from the design charts. Thisis in order to :

5.1. The performance of a pavement can be seriouslyaffected if adequate drainage measures to prevent accumulationof moisture in the pavement structure are not taken. Some ofthe measures to guard against poor drainage conditions aremaintenance of transverse section in good shape to reasonablecrossfall so as to facilitate quick run-off of surface water andprovision of appropriate surface and sub-surface drains wherenecessary. Drainage measures are especially important whenthe road is in cutting or built on low permeability soils orsituated in heavy rainfall/snow precipitation area.

(a) provide the minimum prescribed thickness of sub-base(b) adapt the design to stage construction which necessi tated

some adjustment and increase in sub-base thickness. 5.2. On new roads, the aim should be to construct thepavement as far above the water table as economicallypracticable. The difference between the bottom of subgradelevel and the level of water table/high flood level should,however, not be less than 0.6-1 m. In water logged areas, wherethe sub grade is within the zone of capillary saturation,consideration should be given to the installation of suitablecapillary cut-off as per IRC:34 at appropriate level underneaththe pavement.

Dense Bituminous Macadam shall be constructed in twolayers when the prescribed thickness is more than 100 mm.

4.3.2. The designs relate to CBR values ranging from 2per cent to 1 per cent and ten levels of design traffic1,2,3,5,10,20,30,50,100,150 msa. The pavement compositionsgiven in the design catalogue are relevant to Indian conditions,materials and specifications. Where any change in layer thicknessand specification is considered desirable from practicalconsiderations, the composition can be suitably modified usinganalytical approach with in-service performance related,,:.formation and appropriate design values.

5.3. When the traditional granular construction is providedon a relatively low permeability subgrade, the granular sub-base should be extended over the entire formation width

4243


28/39

IRC:37-2001(Fig. 3) in order to drain the pavement structural section. Careshould be exercised to ensure that its exposed ends do not getcovered by the embankment soil. The trench type sectionshould not be adopted in any case as it would lead to theentrapment of water in the pavement structure.

IRC:37-2001BITUMINOUS SURFAC[NGGRANULAR BASE

If the granular sub-base is of softer variety which mayundergo crushing during rolling leading to denser gradation andlow permeability, the top 100 to 150 mm thickness should besubstituted by an open graded crushed stone layer to ensureproper drainage.

GRANULARSUB-BASE(0) ROAD ON FILL oo SUB-SURFACE DRAINS)

FILTERMATERIAL(WHERE REQUIRED)

Drainage of the pavement structural section can be greatlyimproved by providing a high permeability drainage layersatisfying the following criteria :

BITUMINOUSSURFACINGGRANULAR BASE

: : : 5OPEN GRADEDDRAINAGE LAVEROR SUB-BASED,s of drainage layer

D,s of subgrade (b) ROAD IN CUT (NO SUB-SURFACE DRAINS)To prevent entry of soil particles into the drainage layer

~5BITUMINOUS SURFACINGGRANULAR BASE,s of subgrade

085 of subgrade

050 of drainage layerAnd ~ 5050 of subgrade

-OPEN GRADEDDRAINAGE LAVEROR SUB-BASEFILTER MATERIAL(WHERE REQUIRED )Aggregates meeting the following criteria are regarded asvery good drainage materials : (c) DRAINAGE SYSTEM WITH SUB-SURFACE DRAINS

05 < 4 D,sO2> 2.5 mm Fig. 3 . Drainage of Pavements on Impermeable Subgrade44

45


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IRC:37-2001DS5means the size of sieve that allows 85 per cent by

weight of the material to pass through it. Similar is the meaningof D5o' DI5 and D2 .

IRC:37-2001subgrade at the junction of the verges and the bituminoussurfacing. To counteract the harmful effects of this water, it isrecommended that the shoulders should be well-shaped and ifpossible, constructed of impermeable material. With the sameintent, it is suggested that as far as practicable, and in any caseon major through roads, the base should be constructed 300-450 mm wider than the required bituminous surfacing so thatthe run-off water disperses harmlessly well clear off the maincarriageway.

The permeable sub-base when placed on soft erodiblesoils should be underlain by a layer of filter material to preventthe intrusion of soil fines into the drainage layer (Fig. 3). Non-woven geosynthetic can be provided to act as filter.

5.4. Where large inflows are to be taken care of, anadequately designed sub-surface drainage system consisting ofan open graded drainage layer with collection and outlet pipesshould be provided. The system should be designed on arational basis using seepage principles to estimate the inflowquantities and the outflow conductivity of the drainage system.It should be ensured that the outflow capabilities of the systemare atleast equal to the total inflow so that no free wateraccumulates in the pavement structural section. Sub-surfacedrains using geosynthetics can also be used. Sub-surface drainsshould be constructed to the requirements prescribed in Clause309.3 of the MORT&H Specification for Road and BridgeWorks.

5.7. Shoulders should be accorded special attention duringsubsequent maintenance operation too. They should be dressedperiodically so that they always conform to the requisite cross-fall and are not higher than the level' of carriageway at anytime.

6. DESIGN IN FROST AFFECTED AREAS

5.5. Drainage of existing pavement of 'Trench Type'section on low permeability subgrades can be improved byproviding a continuous drainage layer of 100-150 mm thicknessunder the shoulders at the sub grade level or by providing acombination of longitudinal and lateral drains, the latter spacedat 5 to 6 m intervals. The drains are cut through the shouldersupto the subgrade level and backfilled with coarse drainagematerial.

6.1. In areas susceptible to frost action, the design willhave to be related to actual depth of penetration and severity ofthe frost. At the subgrade level, fine grained clayey and siltysoils are more susceptible to ice formation, but freezingconditions could also develop within the pavement structure ifwater has a chance of ingress from above.

6.2. One remedy against frost attack is to increase thedepth of construction to correspond to the depth of frostpenetration, but this may not always be economically practicable.As a general rule, it would be inadvisable to provide totalthickness less than 450 mm even when the CBR value of thesubgrade warrants a smaller thickness. Inaddition, the materialsused for building up the crust should be frost resistant.

5.6. Very often, water enters the base, sub-base or the46 47


30/39

IRC:37-200 16.3. Another precaution against frost attack is that water

should not be allowed to collect at the subgrade level whichmay happen on account of infiltration through the pavementsurface or verges or due to capillary rise from a high watertable. Whereas capillary rise can be prevented by subsoildrainage measures and cut-offs, infiltrating water can be checkedonly by providing a suitable wearing surface.

(iii) Total pavement thickness forCBR 4% and Traffic 7.2 msa(from Fig; 1)

(iv) Pavement Composition interpolatedfrom Plate 1, CBR 4%(a) Bituminous surfacing(b) Road base(c) Sub-base

7. WORKED EXAMPLES ILLUSTRATINGTHE DESIGN METHOD

IRC:37-2001= 660 mm

= 25 mm SDBC+ 70 mm DBM= 250 mm WBM

= 315 mm granular materia lof CBR not less than30 per cent

Example - 1:Design the pavement for construction of a newbypass with the following data :

Example - 2 : It is proposed to widen an existing 2-laneNational Highway section to 4-lane divided road. Design thepavement for new carriageway with the following data :

DATA(i) Two-lane single carriageway(ii) Initial traffic in the year of

completion of construction(iii) Traffic growth rate per annum(iv) Design life(v ) Vehicle damage factor

(based on axle load survey)(vi) Design CBR of sub grade soil

DESIGN CALCULATIONS(i) Distribution factor (para 3.3.5)(ii)

DATA(i) 4-lane divided carriagway(ii) Initial traffic in each directions in the = 5600 CV/day

year of completion of construction(iii) Design life(iv) Design CBR of subgrade soil(v) Traffic growth rate(vi) Vehicle damage factor

= 400 CV/day(sum of both directions)

= 7.5 per cent= 15 years= 2.5 (standard axles percommercial vehicle)

= 4 per cent (Found out from axle load surveyon existing road)

= 0.75DESIGN CALCULATIONS(i) Distribution factor (para 3.3.5)

Cumulative number of standardaxles to be catered for in the design(Equation given in para 3.3.6.1)N= 365 x [(1+0.075)15-1] x400xO.75x2.5 = 7200000 = 7.2 msa0.075

48

= 10 years/15 years= 5 per cent= 8 per cent= 4.5 (Standard axles per CV)

= 0.75= 4.5ehicle damage factor

Cumulative number of standardaxles to be carried during(a) Design life of 10 yearsN= 365x[(1+0.08)1O_1] x5600xO.75x4.5 = 99.2 msa or say 100 msa0.08

(ii)(iii)

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IRC:37-200 1(b) Design life of 15 yearsN 365 x [(1+0.08),5-1] x5600xO.75x4.5 = 185.6 msa or say 186 msa0.08Pavement thickness and composition(from Fig. 2 and Plate 2) for CBR= 5 per cent and traff ic= 100 msaJ186 msa.(a) For 10 years life

Total Pavement thickness fortraff ic 100 msa (from Fig. 2)CBR 5%

30 per centProvide Total Pavement Thickness = 750 mm

(b) For 15 years life (para 4.3 .4)Accordingly provide pavementthickness and composition for150 msaTotal pavement thickness(from Fig. 2)Composition, (from Plate 2,CBR 5%)Bituminous surfacing

(iv)

Composition (from Plate 2,CBR 5%)Bituminous surfacingBaseSub-base

BaseSub-base

IRC:37-2001Annexure-I

CRITICAL LOCATIONS, RELATIONSHIP BETWEENNUMBER OF CUMULATIVE STANDARD AXLES, STRAINVALUES AND ELASTIC MODULUS OF MATERIALSCritical Locations in Pavement

= 745 mm

= 50 mm BC+ 150 mm DBM= 250 mm WetMix Macadam= 300 mm Granular Sub-baseof CBR not less than

B e . I,--------- -- ----1--- - ---------I1Ie. /"

o eM Al BASE,_________- - --- -4-- --- -- -----

GRANULAR: SUB-BASEII e .I , , , I " II I ,,; ,,~ I , , J , I ; I ; I>;;,

SUBGRAOE

GRANULAR

A and B are the critical locations for tensile strains (EJMaximum value of the strain is adopted for design.= 760 mm C is the critical location for the vertical subgrade strain

(Ez) since the maximum value of the Ez occurs mostly at C.= 50 mm BC+ 170 mm DBM= 250 mmWet Mix Macadam= 300 mm GSB of CBR not

Fatigue Criteria :Bituminous surfacings of pavements display flexural

fatigue cracking if the tensile strain at the bottom of thebituminous layer is beyond certain limit. Based on large amountof field performance data of pavements of south, north, eastless than 30 per cent

Provide Total Pavement Thickness = 770 mm

5150


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IRC:37-2001and wes- zones in India collected under the Research SchemesR-64 and R-195 of Ministry of Surface Transport, Govt. ofIndia the relation between the fatigue life of the pavement andthe tensile strain in the bottom of the bituminous layer wasobtained' as

IRC:37-2001The Poisson's ratio of bituminous layer may be taken as

0.50 for pavement temperatures of 35C and 40C. Fortemperatures from 20C to 30C, a value of 0.35 may beadopted.

2.21 * 10 -4 [ 11 & /8 9 [ 11 E; 08 54 Fatigue equation at any pavement temperature from 200Cto 40C can be evaluated by substituting the elastic modulus ofthe pavement temperature. Catalogue of designs has beenworked out for temperature of 350C.

Where,N F Number of cumulative standard axles to produce 20per cent cracked surface area

Tensile strain at the bottom of BC layer (micro strain)Elastic modulus of bituminous surfacing (MPa) Rutting Criteria :

The above fatigue equation was calibrated at 35C forBituminous Concrete surfacing having 80/100 bitumen and theequation was generalised' by introducing the term containingthe elastic modulus (E) of the bituminous layer so that pavementcan be designed for temperatures from 20C to 40C using anygrade of bitumen.

The values of the elastic moduli of Bituminous Concrete!Dense Bituminous Macadam and Bituminous Macadam meetingthe specifications of the MOST2 are given below',

As large number of data for rutt ing failure of pavementswere obtained from the Research Scheme R-64 of the Ministryof Road Transport and Highways and other researchinvestigations. Setting the allowable rut depth as 20 mm, therutting equation was obtained' as

NR = 4.1656*10-8 [1/~r5337NR = Number of cumulative standard axles to produce ruttingof 20 mmEz = Vertical subgrade strain (micro strainj)

ELASTIC MODULUS (MPa) VALUES OF BITUMINOUS MATERIALS Modulus of Elasticity of Subgrade, SUb-base and BaseLayersSubgrade"

Mix Type Temperature C20 25 30 35 40

Be and DBM 8011 00 bitumen 2300 1966 1455 975 797Be and DBM60/70 bitumen 3600 3126 2579 1695 1270Be and DBM 30/40 bitumen 6000 4928 3809 2944 2276(75 blow compaction and4 per cent air void)BM 80/100 bitumen - - - 500 -BM 60/70 bitumen " 700

E(MPa) = 10*CBR for CBR.::: 5 and= 176*(CBR)064 for CBR > 5

Granular SUb-base and Base?

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IRC:37-2001E2= Composi te Elast ic Modulus of granular Sub-base and Base(MPa)E3 = Elast ic Modulus of Subgrade (MPa)h = Thickness of granular layers (mm)

Poisson's ratio for both the granular layer as well assubgrade layer may be taken as 0.4.Substitution of Dense Bituminous Macadam (DBM) :

Part of the DBM can be substituted for BM on the basisof equal flexural stiffness given as

where,EJH"I1, and E2H2, 112 are the parameters (Elas tic Modulus,Thickness and Poisson's Ratio) of the DBM and BMrespectively. Based on the above equation, followingequivalent thicknesses may be used :

Example180 mm DBM = 125 mm DBM+ 75 mm BM240 mm DBM = 185 mm DBM + 75 mm BM75 mm of BM = 75* (700/1695)1/3 = 55,85 ~ril of DBM

54

IRC:37-2001Annexure-Z

EQUIVALENCE FACTORS AND DAMAGING POWER OFDIFFERENT AXLE LOADS

Gross Axle Weight Load Equivalency FactorsKg. Single Axle Tandem Axle900 0,0002 0,00001810 0.002 0.00022720 0.009 0.0013630 0,031 0.0034540 0.08 0,0065440 0.176 0,0136350 0.35 0,0247260 0,61 0.0438160 1.00 0,0709070 1.55 0.1109980 2,30 0,16610890 3,27 0.24211790 4.48 0,34212700 5,98 0.47013610 7,8 0,63114520 10.0 0,83115420 12,5 1.0816320 15.5 1.3817230 19.0 1.7318140 23.0 2,1419051 27,7 2,6119958 33.0 3.1620865 39,3 3.7921772 46.5 4.4922680 55.0 5.2823587 6.1724494 7,15

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Gross Axle WeightKg.

Load Equivalency FactorsSingle Axle Tandem Axle

IRC:37-2001Annexure-3

IRC:37-2001

25401263082721628123290302993730844317523266033566344733538036288

8.209.410.712.113.715.417.219.221.323.626.128.831.7

PREPARATION OF LABORATORY TEST SPECIMENSGENERAL

1. Wherever possible, the test specimens should be preparedby static compaction, but if not possible, dynamic method maybe used as an alternative.

STATIC COMPACTION2. The weight of wet soil at the required moisture content togive the intended density when occupying the standard testmould is calculated as follows :

In case the class mark of the axle load survey does notmatch with the above axle loads, 4thpower law may be used .forconverting axle loads into equivalent standard axle loads usmgthe following formulae :

Volume of mould = 2209 ccWeight of dry soil = 2209 d gm

100 + mWeight of wet soil = x 2209 d gm

100Single axle loadEquivalency factor = (axle load in kg/8160)4 where,d Required dry density in gm/cc

Required moisture content in per centTandem axle loadEquivalency factor = (axle load in kg/14968)4

The above equations also give reasonably correct resultsfor practical values of axle loads.

3. The soil lumps are broken down and stones larger than 20mm are removed. Sufficient quantity of the soil is mixed withwater to give the required moisture content. The correct weightof wet soil is placed in the mould. After initial tamping with asteel rod, a filter paper is placed on top of the soil, followed bythe 5 em displacer disc, and the specimen compressed in thecompression machine until the top of the displacer is flush with

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IRC:37-2001the top of the collar. The load is held for about 30 seconds andthen released. In some soil types where a certain amount ofrebound occurs, it may be necessary to reapply load to force thedisplacer disc slightly below the top of the mould so that onrebound the right volume is obtained.

IRC:37-2001Annexure-4

SPECIAL POINTS RELATING TO DESIGN OF PAVEMENTON EXPANSIVE SOILS

DYNAMIC COMPACTION Potentially expansive soils, such as, black cotton soils aremontmorillonite clays and are characterised by their extremehar~ess an~ deep cracks when dry and with tendency forheaving dunng the process of wetting. Roadbeds made up ofsuch soils when subjected to changes in moisture content dueto seasonal wetting and drying or due to any other reasonundergo volumetric changes leading to pavement distortioncracking and general unevenness. In semi-arid c1imati~conditions, pronounced short wet and long dry conditionsoccur, whic?aggravate the problem of swelling and shrinkage.Due .recogmtlOn of these problems at the design stage itself isrequired so that counter measures could be devised andincorporated in the pavement structure. A proper designmcorporatmg the following measures may considerably minimisethe problems associated with expansive soils.

4. The soil is mixed with water to give the required moisturecontent, and then compacted into the mould in three layersusing a standard soil rammer. After compaction, the soil istrimmed flush with the top of the mould with the help of ametal straight edge. The mould is weighed full and empty toenable determination of wet bulk density, and from it, knowingthe moisture content, the dry density is calculated.5. Further specimens, at the same moisture content, are thenprepared to different dry densities by varying the number ofblows applied to each layer of soil so that the amount ofcompaction that will fil l the mould uniformly with calculatedweight of wet soil (vide para 2 above) is known.

SUBGRADE MOISTURE, DENSITYAND DESIGN CBRThe amount of volume change that occurs when an

expansive soil road bed is exposed to additional moisturedepends on the following :(a) the dry density of the compacted soil(b) the moisture content(c) structure of soil and method of compaction

58

Expansive soils swell very lit tle when compacted at lowdensities and high moisture but swell greatly when compacted

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IRC:37-2001at high densities and low moisture. Hence, where the probabilityof moisture variation in the subgrade is high, it is expedient tocompact the soil slightly wet of the field optimum moisturecontent determined on the basis of a field trial. Experienceshows that generally, it is not practicable to compact expansivesoils at OMC determined by Laboratory Proctor Test. It is,therefore, necessary to study its field moisture densityrelationship through compacting the soil at different moisturecontents and under the same number of roller passes. Aminimum density corresponding to 95 per cent of the standardproctor density should be attained in the field and recommendedmoisture content should be 1-2 per cent wet of optimummoisture content.

IRC:3 7-20013. Blanket Course

A blanket course of atleast 225 mm thickness andcomposed of coarse/medium sand or non-plastic moorum havingPI less than five should be provided on the expansive soilsubgrade as a sub-base to serve as an effective intrusion barrier.The blanket course should extend over the entire formationwidth.

Alternatively, lime-stabilised black cotton sub-baseextending over the entire formation width may be providedtogether with measures for efficient drainage of the pavementsection.

1. Design CBR 4. DrainageThe pavement thickness should be based on a 4-day

soaked CBR value of the soil, remoulded at placement densityand moisture content ascertained from the field compactioncurve.

Improvement of drainage can significantly reduce themagnitude of seasonal heaves. Special attention should, therefore,be given to provision of good drainage measures as alsodiscussed under Section 5 (Drainage Measures). The desirablerequirements are :

2. Buffer Layer (a) Provision must be made for the lateral drainage of thepavement structural section. The granular sub-baselbaseshould accordingly be extended across the shoulders, refer topara 5.3 of section 5 (Drainage Measures) .

(b) Normal camber of 1:40 for the black top surface and a crossslope of 1:20 for the berms should be provided to shed-offsurface run-off quickly.

(c) No standing water should be allowed on either side of theroad embankment

There is a definite gain in placing the pavement on a non-expansive cohesive soil cushion of 0.6-1.0 m thickness. Itprevents ingress of water in the underlying expansive soil layer,counteracts swelling and secondly even if the underlyingexpansive soil heaves, the movement will be more uniform andconsequently more tolerable. However, where provision ofnon-expansive buffer layer is not economieelly feasible, ablanket course of suitable material and thickness as discussedin para 3 below must be provided. (d) A minimum height of 1 m between the subgrade level andthe highest water level should be ensured.

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IR C:3 7 - 200 I


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5. Bituminous SurfacingDesirably 40 mm thick bituminous surfacing should be

provided to prevent ingress of water through surface.6. Shoulders

Shoulders should be made up of impervious material soas not to allow water to permeate into the body of the pavement.Lime stabilised black cotton soil shoulder of 150-200 mmthickness may serve the purpose economically.

62

Annexure-5RECOMMENDED TYPE AND THICKNESS OF

BITUMINOUS WEARING COURSES FOR FLEXIBLEPAVEMENTS UNDER DIFFERENT SITUATIONS

S l. Type of B ase lN o. B inder C ou rse

T y pe o f B it um i no usW e ar in g C o ur se

Des ignTraffic(msa )

A n nu al R a in fa llLow (L ) lessthan 1 500 m m;M edium (M )1 50 0- 30 00 m m ;H igh (H ) m orethan 3000 m m

I. < 1 0.0

2. B itum inous M acad am (i) S em i-D ense L ,M and H


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In applying the above recommendations, the followingpoints should be kept in view :

(i) In case where a pavement is decided to be developed instages, the surfacing should correspond to that for the designstage.

(ii) As far as possible, wearing course amenable to laying withpaver-finisher should be adopted over paver-f inished baselbinder course.

(iii) Expensive surfacings, like, Bituminous Concrete (BC) shouldnot be provided directly over manually laid granular bases.

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Annexure-6CRITERIA FOR THE SELECTION OF GRADE OF

BITUMEN FOR BITUMINOUS COURSESClimate Traffic (CVD) Bituminous Course Grade of Bitumen

to be usedHot Any : BM, BPM, BUSG 60/70Moderate/Cold Any BM, BPM, BUSG 801100Any Heavy Loads, DBM, SDBC, BC 60/70

Expressways,Urban Roads

HotIModerate Any Premix Carpet 50/60 or 60/70Cold Any Premix Carpet 80/100Hot/Moderate Any Mastic Asphalt 155Cold Any Mastic Asphalt 30/40

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IRC:37-2001REFERENCES

1. Research Scheme R-56 'Analytical Design of FlexiblePavements' Final Report submitted to the Ministry ofSurface Transport (Roads Wing), March 1999, CivilEngineering Department, Indian Institute of Technology,Kharagpur, West Bengal. -

2. Specifications for Road and Bridge Works (ThirdRevision), 1995, Ministry of Surface Transport (RoadsWing), Published by Indian Roads Congress, New Delhi.

3. AASHTO Guide for Design of Pavement Structures,1993 American Association of State Highway andTransportation Officials, Washington DC.

4. Development of Methods, such as, Benkelman BeamMethod for Evaluation of Structural Capacity of ExistingFlexible Pavements and also for Estimation and Design ofOverlays for Strengthening of Weak Pavements, ResearchScheme R-6 of Ministry of Surface Transport (RoadsWing), Final Report submitted by Central Road ResearchInstitute, New Delhi 1995.

5. Pavement Performance Study of Existing PavementSections, Final Report, Volume-2, submitted to the Ministryof Surface Transport (Roads Wing), Central Road ResearchInstitute, New Delhi 1994.

6. IRC:81-1997 "Guidelines for Strengthening of FlexiblePavements Using Benkelman Beam Deflection Technique",Indian Roads Congress, New Delhi.

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IRC:37-200 I7. Shell Pavement Design Manual - Asphalt Pavement and

Overlays for Road Traffic, Shell International PetroleumCompany Ltd., 1978, London.

8. N.W. Lister and W.D. Powell, 'Design Practice for BitumenPavements in the United Kingdom', Proceedings of 6

th

International Conference on Structural Design of AsphaltPavements, Volume 1, 1987.

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Irc 37 2001 Design Flexible Pavements

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