COMPUTER AIDED DESIGN OF LOW VOLUME ROADS

Transcription

1 COMPUTER AIDED DESIGN OF LOW VOLUME ROADS A DISSERTATION Submitted in partial fulfillment of the requirements for the award of the degree of MASTER OF TECHNOLOGY in CIVIL ENGINEERING (With Specialization in Computer Aided Design) By GAJENDRA KUMAR VARSIINEY DEPARTMENT OF CIVIL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY ROORKEE ROORKEE (INDIA) JUNE, 2007

2 CANDIDATE'S DECLARATION I hereby declare that the work which is being presented in the dissertation entitled "COMPUTER AIDED DESIGN OF LOW VOLUME ROADS" in partial fulfillment of the requirement for the award of the degree of Master of Technology in Civil Engineering with specialization in Computer Aided Design, submitted in the Department of Civil Engineering, Indian Institute of Technology, Roorkee is an authentic record of my own work carried out for a period of twe lve months from July 2006 to June 2007 under the supervision of Dr. Praveen Kumar, Associate Professor, Department of Civil Engineering, Indian Institute of Technology, Roorkee. The matter embodied in this dissertation has not been submitted by me for the award of any other degree or diploma. Place: Roorkee Date: o7 (GAJENDRA KUMAR VARSHNEY) CERTIFICATE This is to certify that the above statement made by the candidate is correct to the best of my knowledge. Dr. PRAVEEN KUMAR Associate Professor Transportation Engineering Section Department of Civil Engineering Indian Institute of Technology, Roorkee Roorkee (India)

3 ACKNOWLEDGEMENT I express my deep sense of gratitude and sincere thanks to Dr. Praveen Kumar, Associate Professor, Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee for his expert guidance, keen interest and continuous encouragement enabling me to bring my dissertation into present form. I am grateful to my parents, friends and other well wishes, who form an important part of my life, for their vicarious support and enthusiastic help, without which this work might not have been in its present form. Place: Roorkee 6 0.j.,,ctna Date: (GAJENDRA KUMAR VARSHNEY) ii

4 ABSTRACT Transport infrastructure plays a key role in the economic growth and development of the country. Export, import, industry, agriculture, defense, social services, general administration, maintenance of law and order, exploitation of resource, mobility of persons and goods etc. are some of the many areas of activity which are very closely linked to the availability of adequate transportation system. Among the available modes of transportation, the transport by road is the most versatile one. In India, any road carries less than 450 vehicles per day, called low volume road. Low volume roads are categorized under tertiary road system, which consists of other district roads (ODR) and village roads (VR). India has an essentially rural-oriented economy with 74 per cent of its population living in its villages scattered all over the country. Low volume road is not only the key component of rural development in India; it is also recognized as an effective poverty reduction programme. In the Low Volume Roads, a lot of data have to be analyzed to get optimum design of pavement, overlay and other tasks. Hence a software package was required to be developed to reduce the amount of work, by giving an option to the planner to use the computer, which has been tried here in this dissertation work. The software developed in this dissertation work can be used to perform following tasks of Low Volume Roads: > Cost Comparison between Flexible and Rigid Pavement > Pavement Design Flexible Pavement Rigid Pavement > Overlay Design Benkelman Beam Method CBR Method > Geometric Design Super Elevation > Rate Analysis > Cost Estimation iii

5 CONTENTS CANDIDATE'S DECLARATION ACKNOWLEDGEMENT ii ABSTRACT iii CONTENS iv LIST OF FIGURES vii LIST OF TABLES viii 1. INTRODUCTION General Need of study Objective of study Thesis structure 3 2. LITERATURE REVIEW Definitions Low volume roads All weather and fair weather roads Paved and unpaved Roads Studies Carried Out Abroad General Design Studies Carried out in India General Pradhan Mantri Gram Sadak Yojana Programme objective Features of the PMGSY DESIGN ASPECTS OF LOW VOLUME ROADS Pavement Design Introduction Design parameters Pavements components 15 iv

6 3.2. Design of Flexible Pavement Pavement thickness Surfacing Design of Concrete Pavement Wheel load Tyre pressure Design life Sub grade strength Sub base Concrete strength Critical stresses Overlay Design Benkelman Beam Deflection Technique for Overlay Design Procedure for deflection survey Pavement condition survey Deflection measurements Vehicle damage factor Overlay thickness design curve CBR Method for Overlay Design THE SOFTWARE PACKAGE About Software Salient features of the software Working of the Software Description of Menu options Cost comparison Pavement design Overlay design Project preparation Geometric design Conversion of Curves and Tables in to Mathematical Form Advantage of the Software Source Code of the Software 49

7 5. APPLICATION AND VERIFICATION OF THE SOFTWARE General Pavement Design Flexible pavement design Rigid pavement design Overlay Design Overlay design by Benkelman beam method Overlay design by CBR method Super Elevation Design CONCLUSIONS AND RECOMMENDATIONS Conclusions Recommendations 59 REFERENCE 60 APPENDIX (SOURCE CODE OF THE SOFTWARE) 63 vi

8 LIST OF FIGURES Fig No. Title Page No Moisture correction factor for sandy/gravelly soil subgrade for low rainfall areas (Annual rainfall 1300 mm) Moisture correction factor for sandy/gravelly soil subgrade for high rainfall areas (Annual rainfall > 1300 mm) Moisture correction factor for clayey subgrade for low plasticity (PI<15) for low rainfall areas (Annual rainfall 1300 mm) Moisture correction factor for clayey subgrade for low plasticity (PI<15) for high rainfall areas (Annual rainfall > 1300 mm) Moisture correction factor for clayey subgrade for low plasticity (PI>15) for low rainfall areas (Annual rainfall 1300 mm) Moisture correction factor for clayey subgrade for low plasticity (PI>15) for high rainfall areas (Annual rainfall > 1300 mm) Overlay Thickness Design Curve Form Showing Startup Position Form Showing Menu options Form Showing Cost Compare Results Analysis of Rates Form Cost Estimate Form Super Elevation Form Form showing graphical view for overlay design by CBR method 56 vii

9 LIST OF TABLES Table No. Title Page No Guidelines on surfacing for rural roads Approximate K Value Corresponding to CBR Values Values of co-efficient 'C' based on Bradbury's Chart Recommended Temperature Differentials for Concrete Slabs Criteria for Classification of Pavement Sections Distribution Factor of Commercial Traffic over the Carriageway Indicative VDF values Description of the software Equations for k Value Corresponding to CBR Values Equations for Values of co-efficient 'C' based on Bradbury's Chart Equations for moisture correction factor Equations for overlay thickness Equations for overlay thickness Equations for overlay thickness Equations for overlay thickness Equations for overlay thickness Design Results for Flexible Pavement 51 viii

10 5.2 Design Results for Rigid Pavement Deflection values at typical section Design Results for overlay by Benkelman Beam method Design Results for overlay by CBR method for existing Design Results for overlay by CBR method for widening 57 ix

11 CHAPTER 1 INTRODUCION 1.1. GENERAL Transport infrastructure plays a key role in the economic growth and development of the country. Export, import, industry, agriculture, defense, social services, general administration, maintenance of law and order, exploitation of resource, mobility of persons and goods etc. are some of the many areas of activity which are very closely linked to the availability of adequate transportation system. Among the available modes of transportation, the transport by road is the most versatile one. This mode has maximum flexibility for travel with reference to the route, direction, time and speed of travel. The road network serves as a feeder system for other modes of transportation and as well provides independent facility for road travel by networks of roads throughout the country. Low-volume roads, farm-to-market access roads, roads connecting communities, and roads for logging or mining are significant parts of any transportation system. They are necessary to serve the public in rural areas, to improve the flow of goods and services, to help promote development, public health and education, as well as to aid in land and resource management. [5] In India, any road carries less than 450 vehicles per day, called low volume road. Low volume roads are categorized under tertiary road system, which consists of other district roads (ODR) and village roads (VR). India has an essentially rural-oriented economy with 74 per cent of its population living in its villages scattered all over the country. Low volume road is not only the key component of rural development in India; it is also recognized as an effective poverty reduction programme. The absence of roads in rural areas leads to stagnation of socio-economic conditions of the villages. [22] 1.2. NEED OF STUDY Improvement of quality of life in its villages is one of the toughest challenges for Indian government. It involves alleviation of poverty, generation of employment, improving literacy and modernization of agriculture. A basic road network in rural areas is 1

12 considered absolutely essential for this objective and is major concern of the government. For the agriculture-based economy of the 'country, rural roads play a major role by facilitating the supply of inputs for agriculture, crop diversification, and marketing of agricultural products. For Low volume roads, two types of pavements are used, Flexible pavement and rigid pavement. Generally flexible pavement is used in India. Flexible pavement is designed based on CBR method which described in IRC: SP: and rigid pavement is designed based on IRC: SP: For design of pavement, both methods required so many calculations. For successful maintenance of pavements it is essential that they have adequate stability to withstand the design traffic under prevailing climatic and subgrade conditions. If the pavements have to support increased wheel load and load repetitions, they rapidly undergo the distress and no amount of routine and periodic maintenance can help them. Due to unexpected economic developments in the given region, the loading conditions may become severe and the alternative would be either to divert the traffic on some adjacent routes or to strengthen the existing pavements. Strengthening may be done by providing additional thickness of the pavement of adequate thickness in one or more layers over existing pavement, which is called overlay. In modern age of sophisticated technology, a computer has become the most powerful tool for the data analysis and design. Now-a-days, the scenario of the Computer Aided Design (CAD) is in drastic veer in the field of the computer application. So, there has been a long felt need to develop a user friendly computer package for design of pavement, overlay design, rate analysis and cost estimations. It can make these processes more efficient, less time consuming, more accurate and easier OBJECTIVE OF STUDY The objectives of study are: A. Review of studies on Low Volume Roads 2

13 B. Develop a software for design of low volume roads which includes following modules: a) Cost Comparison between Flexible and Rigid Pavement b) Pavement Design i. Flexible Pavement ii. Rigid Pavement c) Overlay Design i. Benkelman Beam Method ii. CBR Method d) Geometric Design Super Elevation e) Rate Analysis f) Cost Estimation 1.4. THESIS STRUCTURE The composition of the thesis in the following chapters has been so kept that it presents a logical and sequential profile of this dissertation. Chapter 1 describes the introductory notes on low volume roads, design and computer application for design of low volume roads. It also illustrates identification of problem, and objectives and thesis structure. Chapter 2 deals with the literature review. This chapter presents review of research studies related to low volume roads. The work has been done in India for low volume roads. This chapter also describes the Pradhan Mantri Gram Sadak Yojana. Chapter 3 deals with the design aspects for low volume roads. Analysis and design methods of flexible and rigid pavements, overlay design by different methods and super elevation design etc. Chapter 4 deals with the details application steps of the software. It is developed in visual basic. This chapter also contains the detailed steps for conversion of graphs and tables in equations which is required for developing the software. 3

14 Chapter 5 deals with the validation for different modules like pavement design, overlay design and geometric design of software which is developed in chapter 4, with the help of Detailed Project Report for Nawabgang block of Bareilly district of UP state. Chapter 6 deals with conclusions and recommendations. The first part illustrates the points concluded after the development and validation of software for low volume roads and second part shows that what should be the future need related to low volume roads with the work completed in this dissertation. 4

15 CHAPTER 2 LITERATURE REVIEW 2.1. DEFINITIONS Low Volume Roads [4, 22, 321 Low Volume Roads provide the primary links to the highway transportation system. They provide links from homes and farms to markets and for raw materials from forests and mines to mills, and they provide public access to essential health, education, civic, and outdoor recreational facilities. The Low Volume Road link between raw materials and markets is critical to economies locally and nationally in all countries around the world. In developed counties, at the high end, Low Volume Roads may be two-lane asphalt paved roads with up to 2,000 vehicles per day. A widely recognized Low Volume Road definition sets the upper limit at 400 vehicles per day. Many Low Volume Roads around the world consist of a single lane with gravel or even native surfacing. In some remote areas of the world, Low Volume Roads follow travel routes many centuries old. In developing areas, Low Volume Roads may be the first steps up from human and animal pack trails, or they may be all-new roads opening new territory. Even in developed areas, low traffic volumes at the ends of the transportation network may warrant roads with low conventional design standards. [4] In India any road, there is less than 150 people per square-mile, and the road carries less than 450 vehicles per day, called low volume road. Low volume roads are categorized under tertiary road system, which consists of other district roads (ODR) and village roads (VR). Low-volume roads, farm-to-market access roads, roads connecting communities, and roads for logging or mining are significant parts of any transportation system. Other district roads (ODRs): These are roads serving the rural areas of production and providing them with outlet to market centres, block development centre, taluka/tehsil headquarters or main roads. 5

16 Village roads (VRs): These are roads connecting villages and group of villages with each other or to the market centres and with the nearest road of a higher category All Weather and Fair Weather Roads [22] In regard to the interruptions at the cross drainage structures that may be tolerated and the type of pavement surfacing related to rainfall, rural roads are grouped into 'All Weather Roads' and 'Fair Weather Roads' defined as under: All weather roads: At cross drainage structures, the duration of overflow or interruptions at one stretch does not exceed 12 hours for ODRs and 24 hours for VRs in hilly terrain and 3 days in case of roads in plain. The total period of interruption during the year should not exceed 10 days for ODRs and 15 days for VRs. The pavement should consist of metalling (WBM) or higher type where rainfall is more than 150 cm/year and should at least be of material better than local soil, such as moorum, gravel, kankar, laterite etc. where the rainfall is less than 150 cm/year. Fair weather roads: Roads not satisfying the minimum requirements specified above for all-weather roads. These roads should be taken to be in stage of development to be improved subsequently for conversion into all weather type Paved and Unpaved Roads [22] Unpaved or unsealed roads vary from 'clay' roads which can only serve dry season light traffic to heavy duty crushed rock industrial roads which can serve heavy traffic. Typically, such roads are used for providing rural access, carrying an average of 20 to 100 vehicles per day. The base course of such roads is made from local materials e.g. natural gravel and generally using well-tried traditional methods of construction. In sustained wet weather, the unsealed roads may develop deficiencies such as rutting and potholing. On the other hand, in dry seasons, such unsealed roads can become dusty and develop corrugations. Paved or sealed roads are those which are rendered water proof and dustproof by a surfacing or base-cum-surfacing of bituminous materials or cement concrete. 6

17 2.2. STUDIES CARRIED OUT ABROAD General [4, 29] LVRs provide the primary links to the highway transportation system. They provide link from homes and farms to markets and for raw materials from forests and mines to mill, and they provide public access to essential health, education, civic, and outdoor recreational facilities. The LVR link between raw materials and markets is critical to economies locally and nationally in all countries around the world. At the high end, LVRs may be two-lane asphalt paved roads with up to 2,000 vehicles per day. A widely recognized LVR definition sets the upper limit at 400 vehicles per day. Some differentiate urban LVRs from farm-to-market rural LVRs. Many LVRs around the world consist of a single lane with gravel or even native surfacing. In some remote areas of the world, LVRs follow travel routes many centuries old. In developing areas, LVRs may be the first steps up from human and animal pack trails, or they may be all-new roads opening new territory. Even in developed areas, low traffic volumes at the ends of the transportation network may warrant roads with low conventional design standards. LVRs often just evolved, and engineering was an afterthought. Traditionally, LVRs have not provided the volume of business, funding, or glamour to attract and support a specialized field of engineering. When involved with LVRs, engineers used the best information available. They extended their experience and training in higher-standard roads, pavements, or structures to LVR situations, even though they may have recognized the standards as excessive. The Committee on Low-Volume Roads was established to fill this technology gap, to provide a forum for exploring and exchanging experiences on engineering appropriate to LVRs. Interest in LVRs spans the full range of transportation engineering planning, route investigation, geometric design, pavements, structures, construction, operations, maintenance, safety, and so forth. It is essential to adopt the rather nonspecific definition for LVRs to include rather than exclude people in this forum, while recognizing that the actual engineering standards may vary significantly even within the range of LVRs. Hence, developing liaisons with people with expertise in other specific areas of technology is essential. 7

18 The fewer the road users, the less funding is available for road maintenance and restoration, much less engineering. Consequently, LVRs around the world typically need reconstruction and improvement. Many factors in addition to funding further complicate LVR engineering: Whereas they carry only 20 percent of the traffic, LVRs include 80 percent of the transportation system mileage. Although traffic volumes may be low, vehicle loads may be high. Traditional high-volume highway engineering standards may not be appropriate. The highest-volume, highest-rate-of-return proposals receive priority for limited research funding. LVRs often mix unconventional traffic (e.g., farm machinery, bicycles, and oxcarts) with highway passenger cars, buses, and trucks. Few data concerning LVR performance, cost, use, and so forth are available. These challenges provide a wealth of opportunities for enhancing LVR engineering Design [4, 29] Conventional highway geometric design relates increasing standards to increasing speed, volume of traffic, and user comfort and convenience. LVR design focuses on sufficient access; speed, volume, comfort, and convenience do not usually control. Unfortunately, sufficient and flexible design standards have not been widely agreed on for lower-speed, often single-lane, and even gravel-surfaced LVRs. Some initiatives are under way, including the American Society of Civil Engineers and Federal Highway Administration local low-volume roads and streets guide and the ongoing American Association of State Highway and Transportation Officials project. Certainly other LVR standards are used or are being developed in other countries, but they have not been incorporated into U.S. practice. There is some concern about increased tort liability from reduced design standards for LVRs. LVRs provide additional design challenges, such as adequate width for large trucks turning on narrow roads, sharp curves, single-lane roads, pavement markings, and bridge and guardrail standards. 8

19 2.3. STUDIES CARRIED OUT IN INDIA General Rural roads are the tertiary road system in total road network which provides accessibility for the rural habitations to market and other facility centres. In India, during the last five decades, rural roads are being planned and programmed in the context of overall rural development, and tried to provide all-weather connectivity with some level of achievement. The long term road development plans for the country provided policy guidelines and priorities for rural roads, while the funds for rural roads were allocated in the Five Year Plans. [21] Rural Roads have been a neglected sector. The focus given to it through the PMGSY is now enabling the canalization of R&D efforts to this sector. Use of cement concrete, modified bitumen, fly ash as well as soil stabilization techniques and other new methodologies, including Waste Plastic are all be pursued. [20] Recently, during the last five years Government of India has undertaken a dedicated programme known as Pradhan Mantra Gram Sadak Yojana (PMGSY)' to provide rural connectivity to all habitations under the Ministry of Rural Development. More recently, Bharat Nirman, a time bound business plan adopted to provided rural infrastructure during , rural roads have been taken as one of the components and blended with PMGSY programme. It targeted to provide connectivity to all habitations having population of 1000 and above (500 and above in hilly, desert and tribal areas) by 2009 and also aimed to upgrade the existing rural roads for overall network development, which is a more objective approach.[21] To achieve the targets of Bharat Nirman, 1,46,185 km length of rural roads is proposed to be constructed to benefit 66,802 unconnected eligible habitations in the country. It is also proposed to upgrade nearly 1.94 lakh km length of the existing rural roads which are identified as the through routes of the core network. The total investment on rural connectivity under Bharat Nirman has been estimated at Rs. 48,000 crore during Since 11th Five Year Plan ( ) goes beyond the targeted period of Bharat Nirman, assessment of physical targets and upgradation requirements, have been estimated based on the experiences of PMGSY. [21] 9

20 Kumar Anant [17] has done analytical study on effect of regional variation on cost of rural roads under PMGSY, with an attempt to pin point the local factors (such as soil subgrade quality, site clearance, construction of Retaining Wall, Cross Drainage, availability of material etc.), which affects the total cost of rural road construction. A software also had been developed for cost comparison of rural road construction under pmgsy. Jami T.V.Ramakanth [18] have used GIS Software (GeoMedia Professional 5.1) for village area development through prepare thematic map and collect information of block area. It was used for optimal rural road network planning of Vizianagaram District of Andhra Pradesh. Sahoo Umesh Chandra [15] has developed to get the optimum network for rural road connectivity under PMGSY. This software is very useful particularly for large networks. It also provides drainage design. Lal M K [mk] has also developed a software for design of rural roads under PMGSY. It can use for preparation of database for core network identification, preparation of proposal for pavement layers, preparation of summary sheet of the proposals. Saxena Anukul [28] has proposed the planning model for upgradation (strengthening, widening and providing alternate route) of rural roads based on PMGSY program. The model has validated for the Pilana block of the Baghpat district in Uttar Pradesh. For verifying model, a database (village and road information System) was also developed. Core Network upgradation was done and final map was prepared showing the number of roads needs streghtening and widening. Final alternate route was also worked out Pradhan Mantri Gram Sadak Yojana [22, 31] India has an essentially rural-oriented economy with 74 per cent of its population living in its villages and has been systematically planning to provide all its villages and habitations with an all-weather road access. At the commencement of PMGSY, it was estimated that about 330,000 out of its 825,000 villages and habitations were without any all-weather road access. Some States like Punjab and Haryana report full or relatively high 10

21 levels of connectivity. A majority of the poorly connected rural communities lies in ten States (Arunachal Pradesh, Assam, Bihar, Chattisgarh, Jharkhand, Madhya Pradesh, Orissa, Rajasthan, Uttar Pradesh and West Bengal). Construction of rural roads brings multifaceted benefits to the hitherto deprived rural areas and is seen as an effective poverty reduction strategy. The economic benefits of rural roads include increase in agricultural production, changes in cropping pattern, better prices for agriculture produce, reduction in transportation cost, creation of new employment opportunities in farm and off-farm sectors, lower prices for essential commodities for rural consumers, better climate for setting up cottage and agro-industries, increase in production of dairy products, etc. The impact of new link on social life of rural population is reflected in the form of better medical care, more attendance in school/colleges, better availability of public services, higher levels of social interaction etc. Rural roads also change life patterns. Improved connectivity will make daily communication to urban work places easier, reducing migration, increasing rural employment and improving family life. Rural connectivity enables increased penetration of better quality consumer items and durables, thus improving quality of life. Notwithstanding the efforts made, over the years, at the State and Central levels, through different programme, about 40% of the habitations in the country are still not connected by All-weather roads. It is well known that even where connectivity has been provided, the roads constructed are of such quality (due to poor construction ormaintenance) that they cannot always be categorized as All-weather roads. With a view to redressing the situation, Government of India launched the Pradhan Mantri Gram Sadak Yojana on 25th December, 2000 to provide all-weather access to unconnected habitations. The Pradhan Mantri Gram Sadak Yojana (PMGSY) is a 100% centrally sponsored Scheme. 50% of the cess on High Speed Diesel (HSD) is earmarked for this programme. About 1,60,000 habitations are expected to be covered under this programme, with an anticipated investment of Rs. 60,000 crore. This programme is entirely funded by the Government of India. The Central Government formulates the policy guidelines and facilitates the making of good quality roads through insistence on planning, clearance of road works; better methods of execution, time bound 11

22 implementation, and quality control. The planning and execution of road works is carried out by the States Programme Objectives [22, 31] The primary objective of the PMGSY is to provide connectivity, by way of an allweather road (with necessary culverts and cross-drainage structures, which is operable throughout the year), to the eligible unconnected habitations in the rural areas, in such a way that all unconnected habitations with a population of 1000 persons and above are covered in three years ( ) and all unconnected habitations with a population of 500 persons and above by the end of the tenth plan period (2007). In respect of the hill States (North-East, Sikkim, Himachal Pradesh, Jammu & Kashmir, Uttaranchal) and the desert areas (as identified in the Desert Development Programme) as well as the Tribal (Schedule V) areas, the objective would be to connect habitations with a population of 250 persons and above. The PMGSY will permit the upgradation (to prescribed standards) of the existing roads in those Districts where all the eligible habitations of the designated population size have been provided all-weather road connectivity. However, it must be noted that upgradation is not central to the programme and cannot exceed 20% of the State's allocation as long as eligible unconnected habitations in the State still exist. In upgradation works, priority should be given to through routes of the rural core network, which carry more traffic Features of the PMGSY [22, 31] The Ministry of Rural Development (MoRD) has been entrusted with the task of organizing the programme. Some of the noteworthy features of the programme are: Full central funding, with 50% of the cess on High Speed Diesel being earmarked for this programme. Preparation of master plans and core network for rural roads for all the Districts and Blocks, identifying the unconnected habitations and proposing the most cost - effective routes for the purpose. 12

23 Design and specifications as contained in the Rural Roads Manual (RRM, IRC SP: 20), published by the Indian Road Congress (IRC). Appointment of programme implementing agencies, by all States typically Public Works Departments (PWDs) or Rural Engineering Organizations (REOs). Appointment of a dedicated State level agency in all states with over all responsibility for rural road planning, programme execution and management. Use of competitive tendering by the implementing agencies of all works on basis of a Standard Bidding Document (SBD). Execution of the works within a period of 9-12 months. A defects liability and maintenance period of 5 years specified in the contracts for the roads constructed under the programme, with funds for maintenance being provided by the states. A 3 tier Quality management system. 13

24 CHAPTER 3 DESIGN ASPECTS OF LOW VOLUME ROADS 3.1 PAVEMENT DESIGN Introduction 19] The road structure may be divided into four major components, viz., land, earthwork, pavement and cross drainage works. The pavement constitutes nearly one-third to one-half of the total cost of the road. Therefore, very careful consideration should be there for the choice of the type of pavement and its design The factors which govern the selection of the type of the pavement are: (a) Initial (construction) cost (b) Availability of good materials locally (c) Cost of maintenance or rehabilitation during service (d) Technology of construction required and its availability The options available for low volume roads are: (a) Flexiblepavement (b) Cement concrete pavement In case of rural roads, in view of the stage development strategy and the initial cost advantage, the flexible pavement may be the appropriate choice. However, in special cases, in short sections or in some rural road projects where the ground conditions and material availability may pose restriction for use of flexible pavement, the other options like roller compacted concrete, block pavements and composite pavements may be cost effective. Generally the choice of pavement will be further guided by several other factors, such as (a) Rainfall and temperature (b) Type and strength of soil along the alignment (c) Availability of good aggregates 14

25 (d) Availability of industrial wastes (like, fly ash, slag, etc.) in the proximity The importance of pavement design, even for rural roads, cannot be overemphasized While it appears that rural roads will not have traffic intensity or axle loads as compared to higher categories of road, even small number of commercial vehicles (or tractor-trolley) with heavy axle loads or iron-tyred animal drawn cart may cause heavy damage to an under designed pavement. It is due to this single most important reason that a considerable length of rural roads built every year using resources of different rural development programmes failed prematurely. Any design using conventional, marginal or waste material must follow standard procedure based on material property, traffic and design life. There are many associated factors like rainfall, ground water table, etc. which are also to be taken into account for evolving durable pavement design. In all designs, economy in the initial cost as well as in life cycle cost are crucial and very important. These aspects assume extra emphasis in case of rural roads Design Parameters [9] (A) General: The principal criterion for determining the thickness of a flexible pavement with a thin bituminous surfacing is the vertical compressive strain on top of the subgrade imposed by a standard axle load of magnitude 8.17 kn (8170 kg). Excessive vertical subgrade strain causes permanent deformation in the subgrade, which is manifested in the form of rutting on the pavement surface. The maximum rutting that can be accepted in village roads may be taken as 50 mm before rehabilitation work is needed. Analytical evaluation of performance of other district roads and village roads on the basis of the vertical subgrade strain criterion has indicated that the design curves as per IRC: 37 are generally valid for the design traffic from 0.1 million standard axles (msa) to 2 msa. However, for design of rural roads, the design charts have to be simple and convenient for the grass-root level agencies.. Road Note 29 of TRL, IRC: 37 and experience in India suggests that the charts may be for the traffic in the range up to 450 CVPD. Since subgrade CBR may be as high as 20 per cent, design curves are also prepared for subgrade CBR up to 20 per cent. The minimum recommended pavement thickness is 150 mm even when design chart gives 15

26 lower thickness. For rigid and semi-rigid pavements tensile stress is taken as the design criteria to prevent fracture of the concrete layer within the design period. In. case of concrete block pavements, vertical subgrade strain is the critical criterion to limit rut depth due to traffic loading. (B) Traffic: For the purpose of structural design, only the number of commercial vehicles of laden weight 3 tonnes or more should be considered. To obtain a realistic estimate of design traffic, due consideration should be given to the existing traffic and its rate of growth. In case of new construction, anticipated traffic, possible changes in the road network and land use of the area served as well as the probable growth of traffic over design life are to be carefully accounted for. If adequate data is not available, an average value of 6 per cent may be adopted for traffic growth rate. (C) Design life: Design life is usually defined as the number of years until the first major reconstruction is anticipated. For unsurfaced roads, aggregates are displaced on either side of the wheel path and frequent blading is necessary to maintain a good riding surface. For unsealed/unsurfaced roads aggregates are often lost due to traffic action as well as erosion by rains, and the pavements become thinner with time. Material lost must be replenished periodically to maintain the rideability. It is necessary that sufficient thickness is provided to prevent rutting failure during the design life due to high vertical subgrade pressure. It is considered appropriate that roads in rural areas should be designed for a design life of 10 years. The thin bituminous surfacing that is commonly provided on the low volume roads has a life of about 5 years. (D) Computation of design traffic: The design traffic is considered in terms of the future traffic to be carried during the design life of the road. Its computation involves estimates of the initial volume of commercial vehicles per day, traffic growth rate and design life in years. In case of rural roads the commercial vehicles will be trucks (small and big), buses and tractor-trolley. The traffic for the design life is computed as: P (l+r) 16

27 Where A= Number of commercial vehicles per day for design P = Number of commercial vehicles per day at last count r = Annual growth rate of commercial traffic n = Number of years between the last count and the year of completion of construction x = design life in years Since the width of rural roads will be single lane, design traffic should be based on total number of commercial vehicles per day in both directions. Bullock carts with iron rims are still in use in different parts of the country and the total weight including the pay load of a bullock cart may range from 1.0 tonne to 1.5 tonnes. Though the designed pavement as a whole will be safe from shear failure, the iron rims damage the top layer of the pavement because of high concentration of stress. Thus the wearing course must be made up of good quality aggregates with aggregate impact value not exceeding 30 per cent to reduce degradation of the aggregates by crushing Pavements Components [9] (A) Subgrade: In rural roads, the top 30 cm of the cutting or embankment at the formation level shall be considered as subgrade. The subgrade, whether in cut or fill, should be well compacted to utilize its inherent strength and prevent permanent deformation because of additional compaction by traffic. A minimum of 100 per cent of Standard Proctor compaction should be attained in the top 30 cm of the subgrade. For clayey soil, the minimum compaction for subgrade should be 95 per cent of Standard Proctor compaction and the compaction should be done at moisture content 2 per cent in excess of the optimum value. For embankments, the soil below 30 cm of subgrade shall be compacted to minimum 97 per cent of Standard Proctor compaction [IS: 2720 (Part 7)-1980]. For pavement design, the subgrade strength should be determined in terms of CBR at the most 17

28 critical moisture conditions likely to occur. The CBR test should be conducted on remoulded samples prepared at optimum moisture content and dry density corresponding to Standard Proctor compaction [(IS:2720 (Part 7)-1980] and soaked in water for four days prior to testing. If the annual rainfall is of the order of 500 mm or less and the water table is too deep, soaking for four days may not be necessary. One or two CBR tests should be done per kilometer depending on the variation of soil type. If there is no variation in soil type, mean CBR value should be adopted for the design of pavements. In case of existing roads requiring strengthening, the soil should be moulded at the existing moisture content and field density, and soaked for four days prior to testing for CBR. Where the CBR of the subgrade is less than 2 per cent a capping layer of 100 mm thickness of material with a minimum CBR of 10 per cent is to be provided in addition to the sub-base required for CBR of 2 per cent. If the subgrade CBR is more than 15 per cent, there is no need to provide a sub-base. WBM base can be laid directly over the subgrade after providing a drainage layer (inverted choke). (B) Sub-base: Sub-base is a layer of selected material placed on the subgrade compacted to 98 per cent of the IS heavy compaction. Generally it consists of locally availablq relatively low strength inexpensive material. The principal function of the sub-base is to distribute the stresses over a wide area of the subgrade imposed by traffic and to ensure that no subgrade material intrude into the base course and vise versa. There are a large number of locally available aggregates and industrial waste materials that can be utilized for sub-bases of pavements. The sub-base material should have minimum soaked CBR of 15 per cent. Material component of sub-base passing 425 micron IS sieve when tested in accordance with [IS: 2720 (Part 5)-1985] should have liquid limit and plasticity index not more than 25 and 6 respectively. These requirements should be enforced to achieve desired quality. When the subgrade is silty or clayey soil and the annual rainfall of the area is more than 1000 mm, a drainage layer of 100 mm over the entire formation width should be 18

29 provided conforming to the gradation. This layer will form a part of the designed thickness of sub-base. (C) Base: The base course materials should be of good quality so as to withstand high stress concentrations which develop immediately under the wearing surface. Since bituminous surfacing consists only of a thin wearing course, the upper surface of the base must be sufficiently smooth and true to profile to provide a good riding surface. The different types of base course which are commonly Used are: (a) Water Bound Macadam (WBM) (b) Crusher-Run Macadam (c) Dry Lean Concrete (d) Soft Aggregate Base Course (e) Lime-Fly Ash Concrete Thickness deduced from the design charts are appropriate to pavements with unbound granular bases which comprise of conventional WBM or any other equivalent granular construction. For cement treated or stabilized materials, thorough laboratory investigations are necessary and the pavement design can be done using analytical method. In some situations where good quality aggregates are not available, cement treated low grade aggregates or soils may also be used. Appropriate agency may be approached for laboratory investigations and design. It is recommended that normally no material with CBR value less than 100 per cent should be used in base courses. Since base course will be affected by water, their strength should be determined in soaked condition. Where a substantial part of the base material consists of particles larger than 20 mm size, the CBR test will not be applicable and their strength will have to be estimated from experience. WBM of adequate thickness over a properly designed sub-base will be assumed to satisfy the CBR requirements of 100 per cent. The design of base courses of different types are given in subsequent Sections. (D) Pavement surface: Pavement can be with a sealed or unsealed surface. The unsealed surface means a granular surface where percolation of water into the pavement layers is 19

30 possible, whereas in sealed surface it is prevented by appropriate surfacing layer. Details of the design or choice of surfacing are given in Section DESIGN OF FLEXIBLE PAVEMENT [9] Pavement Thickness: The thickness of pavement is designed on the basis of projected number of commercial vehicles for the design life using the current commercial vehicles per day and its growth rate. Further, it requires the subgrade strength value in terms of CBR. It is expected that rural road will not have more than 450 CVPD in any case. The design chart may be referred to obtain the total pavement crust thickness (granular crust thickness) required over the subgrade for the design life of the pavement. Based on the strength of granular materials that are used, the total design thickness is divided into base and sub-base thicknesses. However, any other higher type of bituminous layer can be part of the designed thickness, with the exception of thin bituminous surfacing (PMC, MSS, etc.). In case of rural roads, with low volume of traffic, structural layer of bituminous mix need not be provided, generally except in very special cases where the traffic volume is so high that the design suggests it Surfacing: A gravel road or WBM layer can serve adequately as a surfacing depending on traffic volume. However, it is to be clearly understood that granular materials (like, soil-gravel mixture) will be lost gradually by traffic action and thickness will be reduced. Therefore, for gravel roads extra thickness should be provided. Further, for similar reasons, only WBM Grade-III should be used as a surfacing course for an unsealed WBM road. Other granular surfacing, like, Moorum, Kankar, etc. will have to be bladed as and when required to provide smooth riding surface. The bituminous wearing course will generally consist of premix carpet with seal coat or two coat surface dressing laid over WBM base course or other type of bases. Bituminous wearing course must be made up of good quality aggregates with aggregate impact value not exceeding 30 per cent in order to reduce degradation of the aggregates by crushing Use of bituminous emulsion for such work may give good surfacing because of processing of material at ambient temperature. Maintaining the right mixing temperature of the hot mix is not easy when the dampness of aggregates stacked at the sites varies. Based on the total motorized traffic and rainfall, an appropriate surface course can be chosen from Table

31 Table 3.1. Guidelines on surfacing for rural roads Annual Rainfall (mm) Thin Bituminous Surfacing (2-Coat S.D.) Single Coat Surface Dressing Unsealed Surface (Gravel Road) Unsealed Surface (Gravel Road) Note: S.D. = Surfacing Dressing Bituminous Surfacing (PMC + Seal Coat) Thin Bituminous Surfacing (2-Coat S.D.) Single Coat Surface Dressing Unsealed Surface (Gravel Road) Bituminous Surfacing (PMC + Seal Coat) Bituminous Surfacing (PMC + Seal Coat) Thin Bituminous Surfacing (2-Coat S.D.) Thin Bituminous Surfacing (2-Coat S.D.) Motorized Traffic (Except 2-Wheeler) per Day PMC = Premix Carpet 3.3. DESIGN OF CONCRETE PAVEMENT [10] The Guidelines contained in IRC: are essentially intended for high volume heavily trafficked highways. They are likely to result in uneconomical designs for the low volume Rural Roads. The Rigid Pavements Committee of the IRC has recently finalized the guidelines for the design and construction of concrete pavements for Rural Roads (IRC: SP: ). Though they are yet to be published, they can be used for the PMGSY programme. Keeping this in view, the essential features of the design guidelines are given below Wheel Load: The legal axle load in India being 102 kn, the pavement may be designed for a wheel load of Si kn. However, for link roads serving isolated villages where the traffic consists of agricultural tractors and trailers and light commercial vehicles only, a design wheel of 30 kn may be considered Tyre Pressure: The tyre pressure may be taken as 0.7 MPa where a wheel load 51 kn is considered and 0.5 MPa where a wheel load of 30 kn is considered Design Life: Concrete pavements designed as per these guidelines are expected to have a life of at least 20 years. 21

32 Subgrade Strength: The approximate value of the Modulus of Subgrade reaction, k, may be obtained from its soaked CBR value as per the Table 3.2. Table 3.2 Approximate K Value Corresponding to CBR Values Soaked CBR % k Value Nimm2/mm x Sub-Base: A sub-base of 75mm thick of Water Bound Macadam (Grade III: mm size aggregates), Wet Mix Macadam, gravel, murram, soil-cement or soil-lime is recommended. Where loaded heavy trucks are expected, this thickness may be increased to 150mm. The surface may be primed with bituminous primers to render it smooth. Where the sub-base is provided, the effective k value may be taken as 20% more than the k value of the sub-grade. A plastic sheet of 125 microns thickness shell be provided over the subbase to act as a separation layer between the sub-base and concrete slab Concrete Strength: Since concrete pavements fail due to bending stresses, it is necessary that their design based on the flexural strength of concrete. Where there are no facilities for determining the flexural strength, the mix design may be carried out using the compressive strength values and the following relationship: f f = 0.7-rfc, Where, f f = flexural strength, N/mm2 f, = characteristic compressive cube strength, N/mm2 The minimum 28-day compressive strength of concrete shall be 25 MPa, which gives a flexural strength of 3.0 MPa. For Low Volume Roads, it is suggested that the 90-day strength be used for design instead of the 28-day strength as the traffic develops only after the lapse of a period of time. The 90 days flexural strength may be taken as 1.20 times of 28-day flexural strength Critical Stresses: The slab may be checked for: 22

33 (a) A combination of edge load and temperature stress (b) Corner load Edge load stress: it can be calculated from the Westergaard's Formula: sle = (1+0.54,u)(4logio 1+logio b ) 112 Where, sle = edge load stress in MPa P = design wheel load, N h = pavement slab thickness, mm m = Poisson's ratio, may be taken as 0.15 E = Modulus of elasticity of concrete, MPa which may be taken as 3.0x104 MPa k = Modulus of subgrade reaction, N/rnm3x10-3 1= radius of relative stiffness, mm Eh' 12(1 // 2 )k b = radius of equivalent distribution of pressure = a for a h = 1/1.6a 2 +h h for < And a = radius of load contact assumed circular, mm 1 P ' / 2 = where p is tyre pressure Pa" i 23

34 Corner load stress 3P s/c = (a-5\12 Where, slc = load stress in the corner region, MPa Temperature stress ste= EaAtC 2 Where, ste = temperature stress in the edge region, At = maximum temperature differential during day between top and bottom of the slab, a = Coefficient of thermal expansion of concrete, C = Bradbury's coefficient, which can be ascertained directly from Bradbury's chart against values of L/1 and W/1 L = slab length or spacing between consecutive contraction joints W = slab width 1= radius of relative stiffness in Table 3.3 Values of the coefficient C based on the curves given in Bradbury's chart, are given Table 3.3 Values of co-efficient 'C' based on Bradbury's Chart 111 and W/I C

35 and above Temperature differential between the top and bottom of concrete pavements causes the concrete slab to warp, giving rise to stresses. The temperature differential is a function of solar radiation received by the pavement surface at the location, losses due to wind velocity, etc., and thermal diffusivity of concrete, and is thus affected by geographical features of the pavement location. As far as possible, values of actually anticipated temperature differentials at the location of pavement should be adopted for pavement design. For this purpose guidance may be had from Table 3.4. Table 3.4 Recommended Temperature Differentials for Concrete Slabs Zone I States Punjab, U.P., Uttarakh and, Haryana, Gurarat and North M. P., excluding hilly regions. Temperature Differential, t') C in Slabs of Thickness 150 mm 200 mm 250 mm II III IV Bihar, Jharkand, West Bengal, Assam and Eastern Orrissa excluding hilly regions and coastal areas. Maharashtra, Karnataka, South M.P., Chattasgarh, Andhra Pradesh, Western Orissa, and North Tamil Nadu excluding hilly regions and coastal areas. Kerala and South Tamil Nadu excluding hilly regions and coastal areas V Coastal areas bounded by hills VI Costal areas unbounded by hills

36 3.4. OVERLAY DESIGN For successful maintenance of pavements it is essential that they have adequate stability to withstand the design traffic under prevailing climatic and subgrade conditions. If the pavements have to support increased wheel load and load repetitions, they rapidly undergo the distress and no amount of routine and periodic maintenance can help them. Due to unexpected economic developments in the given region, the loading conditions may become severe and the alternative would be either to divert the traffic on some adjacent routes or to strengthen the existing pavements. Strengthening may be done by providing additional thickness of the pavement of adequate thickness in one or more layers over existing pavement, which is called overlay. The method of overlay design is given below: > Benkelman beam deflection technique > CBR method 3.5. BENKELMAN BEAM DEFLECTION TECHNIQUE FOR OVERLAY DESIGN Procedure for Deflection Survey [8] The deflection survey essentially consists of two operations: (i) Condition survey for collecting the basic information of the road structure and based on this, the demarcation of the road into sections of more or less equal performance; and (ii) Actual deflection measurements Pavement Condition Survey [8] This phase of operation which precedes the actual deflection measurement, consists primarily of visual observations supplemented by simple measurements for rut-depth using a 3 meter straight edge. Based on these, the road length shall be classified into sections of equal performance in accordance with the criteria given in Table 3.5 [9]. 26

37 TABLE: 3.5. Criteria for Classification of Pavement Sections. Classification GOOD FAIR POOR Pavement condition No cracking, rutting less than 10mm No cracking or cracking confined to single crack in the wheel track with rutting between 10mm and 20mm. Extensive cracking and/or rutting greater than 20mm. Sections with cracking exceeding 20 percent shall be treated as failed Deflection Measurements [8] In each road section of uniform performance, minimum of ten points are marked at equal distance in each lane of traffic for making the deflection observations in the outer wheel path. The interval between the points should not be more than 50m. On roads having more than one lane, the points marked at adjacent lanes should be staggered. In the transverse direction, the measurement points should be 60 cm from the pavement edge if the lane width is less than 3.5 m and 90 cm when the lane width is more than 3.5m. For divided four lane highway the measurement points should be 1.5 m from the pavement edge. For measuring pavement deflection the C.G.R.A procedure which described in IRC: is adopted. A standard truck having a rear axle weighing 8170 kg fitted with dual tyre inflated to a pressure of 5.60 kg/cm2 is used for loading the pavement. During actual tests, the total load and the tyre pressure are maintained within a tolerance of ±1 percent and 1 5 percent respectively. The deflection data so obtained are corrected for temperature and soil condition at the time of experiment [9]. (A) Correction for temperature variations Deflections measured by the benkelman Beam are influenced by the pavement temperature. For design purposes, therefore, all deflection values should be related 27

38 to a common temperature. Measurements made when the pavement temperature is different than standard temperature would need to be corrected. The stiffness of bituminous layers changes with temperature of the binder and consequently the surface deflections of a given pavement will vary depending on the temperature of the constituent bituminous layers. For purposes of design, therefore, it is necessary that the measured deflections to be corrected to a common standard temperature. For areas in the country having a tropical climate, the standard temperature is recommended to be 35 C. Correction for temperature is not applicable in the case of roads with thin bituminous Surfacing. Temperature correction is required for pavements having a substantial thickness of bituminous construction (i.e. minimum 40 mm) [8]. Available information shows that the deflection-pavement temperature relationship is linear above a temperature of 30 C. For convenience in the application of the temperature correction, it is recommended that the deflection measurements should be taken when the pavement temperature is within the range of 30 C to 35 C, preferably when the temperature is uniform and is near the temperature of 35 C. Accordingly, as far as possible deflection measurements should be made during morning and evening hours on summer months. Correction for temperature variation on defection values measured at pavement temperature other than 35 C should be 0.01 mm for each degree centigrade change from the standard temperature of 35 C. The correction will be positive for pavement temperature lower than 35 C and negative for pavement temperature higher than 35 C. In colder areas, and areas of altitude greater than 1000m where average temperature is less than 20 C for more than 4 months in a year, the standard temperature of 35 C does not apply [8]. In the absence of adequate data about deflection performance relationship, it is recommended that the deflection measurements in such areas be made when the ambient temperature is greater than 20 C and that no correction for temperature is applied. 28

39 (B) Correction for seasonal variation Since the pavement deflection is dependent upon change in the climatic season of the year, it is always desirable to take deflection measurements during the season when the pavement is in its weakest condition. Since, in India, this period occurs soon after monsoon, deflection measurements should be confined to this period as far as possible. When deflections are measured during the dry month, they will require a correction factor which is defined as the ratio of the maximum deflection immediately after monsoon to that of the minimum deflection in the dry months. Correction for seasonal variation depends on type of subgrade soil, its field moisture content (at the time of deflection survey) and.average annual rainfall in the area. For this purpose, subgrade soils are divided into three broad categories, namely sandy/gravelly, clayey with low plasticity (PI < 15) and clayey with high plasticity (PI > 15). Similarly, rainfall has been divided into two categories namely low rainfall (annual rainfall < 1300 mm) and high rainfall (annual rainfall > 1300 mm) The correction factor for different condition of soil type and rainfall are obtained by making use of the curves given in Fig 3.1 to 3.6. The deflection values corrected for temperature are multiplied by the appropriate values of seasonal correction factor to obtain corrected values of deflection [8]. Fig : Moisture correction factor for sandy/gravelly soil subgrade for low rainfall areas (Annual rainfall 1300 mm) 29

40 Fig : Moisture correction factor for sandy/gravelly soil subgrade for high rainfall areas (Annual rainfall > 1300 mm) Fig. 3.3: Moisture correction factor for clayey subgrade for low plasticity (Pl[<15) for low rainfall areas (Annual rainfall mm) r.-" "*"*. "-----7r- ' A Fig.3.4: Moisture correction factor for clayey subgrade for low plasticity (PI<15) for high rainfall areas (Annual rainfall > 1300 mm) 30

41 e A.. JY: X 'A, 5';,5 Fig. 3.5: Moisture correction factor for clayey subgrade for low plasticity (PI>15) for low rainfall areas (Annual rainfall 1300 mm) 2 t: :, 4 7. Fig. 3.6: Moisture correction factor for clayey subgrade for low plasticity (PI>15) for high rainfall areas (Annual rainfall > 1300 mm) (C) Characteristic Deflection Overlay design for a given section is based not on Individual deflection values but on a statistical analysis of all the measurements in section corrected for temperature and seasonal variations. This involves calculation of rebound deflection, mean deflection, standard deviation and characteristic deflection. The three deflection dial reading Do, Di and Df form a set of readings at one deflection point under consideration. The rebound deflection value D 21 any point is given by one of the following two conditions: (a) if Di - D f 0.025mm 31

42 Dr= 0.02(D0- Df) mm (b) if Di - Df> 0.025mm Dr = 0.02(D0 - Df) (D. - Df) mm Corrected rebound deflection Dre = [Dr+ (35-T) x0.01] xm.c.f. Mean deflection, x = n xi 1/(x _ x.)2 Standard deviation, a = n- 1 Characteristic deflection For major arterial roads (like NH and SH) - Dc =x+2c For all other roads - Dc = x + a Where, Dr = rebound deflection mm Dr. = corrected rebound deflection mm x = mean deflection mm n = number of deflection measurements a = standard deviation, mm De = characteristic deflection, mm T = temperature in degree centigrade M.C.F. = moisture correction factor (D) Estimation of Cumulative Number of Standard Axle 32

43 Traffic in terms of million standard axle is considered for the design of overlay. For the purposes of the design, only the number of commercial vehicles of laden weight of 3 tonnes or more and their axle loading are considered. Traffic is considered in both directions in the case of two lane road and in the direction of heavier traffic in the case of multilane divided highways. To obtain a realistic estimate of design traffic due consideration should be given to the existing traffic, possible changes in road network, land use of the area served, the possible growth of traffic and design life. Estimate of the initial daily average traffic flow for any road is normally be based on 7-day 24-hours classified traffic counts. However, in exceptional cases where this information is not available 3-day count could be used. The design traffic is considered in terms of the cumulative number of standard axles to be carried during the design life of the road. The following equation may be used to make the required calculation [8]. 365A[(1+ 1]F Ns = r where, Ns = the cumulative number of standard axles to be catered for in the design. A = Initial traffic, in the year of construction, in terms of the number of commercial vehicles per day duly modified to account for lane distribution as given in Table 3.2 [4] r = annual growth rate of commercial vehicles. x = design life in years. F = Vehicle damage factor (number of standard axles per commercial vehicle) 33

44 The distribution of commercial traffic over the carriageway is another important consideration for design of overlay as it directly affects the total equivalent standard axle load applications used in the design. Table 3.6: Distribution Factor of Commercial Traffic over the Carriageway No. of lanes Single lane roads Two lane single carriageway roads. Four lane single carriageway roads Dual carriageway roads Design traffic in CVPD Total in both direction 75% of total traffic 75% of total traffic 75% of total traffic in one direction Vehicle Damage Factor Vehicle damage factor (VDF) is a multiplier for converting the number of commercial vehicles of different axle loads to the number of standard axle/load repetitions. The vehicle damage factor is arrived at from axle-load surveys on typical road-sections so as to cover various influencing factors such as traffic mix, type of transportation, type of commodities carried time of the year, terrain, road condition and degree of enforcement. For designing a strengthening layer on an existing road pavement, the vehicle damage factor should be arrived at carefully by using the relevant available data or carrying out specific axle load surveys depending upon importance of the project. Where sufficient information on axle load is not available, the tentative indicative values of vehicle damage factor as given in table 3.7 [9] may be used. Table 3.7: Indicative VDF values Initial traffic intensity in terms of number of Terrain commercial vehicles per day (Traffic range) Rolling/Plain Hilly More than

45 3.5.6 Overlay Thickness Design Curve The thickness of overlay is found from the design curves relating characteristic pavement deflection to the cumulative number of standard axles to be carried over the design life as given in Fig.3.7 [9]. The thickness deduced from this is the overlay thickness in terms of bituminous macadam construction. In case other compositions are to be laid for strengthening, the equivalent overlay thickness to be provided may be determined using equivalency factors as suggested below 1 cm of BM = 1.5 cm of WBM/WMM/BUSG 1 cm of BM = 0.7 cm of DBM/AC/SDC From structural considerations, the recommended minimum bituminous overlay thickness is 50 mm BM with additional surfacing course of 50 mm DBM or 40 mm bituminous concrete. Fig. 3.7: Overlay Thickness Design Curve 35

46 3.6. CBR METHOD FOR OVERLAY DESIGN [9] This method can be used for overlay design for strengthening and widening of existing road. Design process is the same as flexible design method. Total thickness of existing pavement is calculated, and then required thickness of pavement is found. Total thickness of existing pavement is subtracted from designed crust thickness. Thickness of sub base and base is rearranged according to Gl, G2 and G3 layer. For widening part, pavement design is the same as new pavement. 36

47 CHAPTER 4 DEVELOPMENT OF SOFTWARE PACKAGE 4.1. ABOUT THE SOFTWARE The software is developed in Visual Basic 6. It has user friendly window based Graphical User Interface (GUI). Microsoft Access is used for storage, manipulation and retrieval of data. Crystal Report is used for reporting data Salient Features of the software This software can be used to perform following tasks related to design of Low Volume Roads. I. Cost Comparison Cost Comparison between Flexible Pavement and Rigid Pavement II. Pavement Design Flexible Pavement Design Rigid Pavement Design III. Overlay Design Benkelman Beam Deflection Method CBR Method IV. Geometric Design Super Elevation Design V. Analysis of Rates VI. Cost Estimation of Roads 37

48 4.2. WORKING WITH SOFTWARE Description of the Menu Options Table 4.1. Description of the software S. No. Menus Sub Menus Function 1. Cost Compare Open forms for cost comparison - between flexible pavement and rigid pavement 2. Pavement Design Flexible Pavement Opens form to get detail design of the flexible pavement design as per IRC SP : Rigid Pavement Opens form to get detail design of the rigid pavement design as per IRC SP : Overlay Design Benkelman Beam Opens the forms for detail design of Method flexible overlay over flexible pavement by Benkelman Beam method as 'RC: CBR Method Opens the forms for detail design of flexible overlay over flexible pavement by CBR method as per IRC SP: Geometric Design Super Elevation Opens the form for design of super elevation at curves as per IRC SP: Rate Analysis _ Opens form for analysis of rates in FORMAT F-8 6. Cost Estimate Opens form for cost estimation in FORMAT F-6 7. Help Help file containing various provisions for Low Volume Roads as per IRC 38

49 CAD q. Low Volume Roads: Version Please wait Company - IITR Fig 4.1. Form Showing Startup Position Fig 4.2. Form Showing Menu options Cost Comparison: Cost comparison form can be activated by clicking "Cost Compare" menu. User can compare between cost of flexible and cost of rigid pavement for inputs. If rate of item is already known then user can direct use rates, otherwise user can also calculate rate of item through software. If rate of item is already available it will be 39

50 displayed. Software provides results in tabular as well as graphical format. So user can take decision that which one is economy., ' \... iiipar; YM...C ,0 ie:favemen, : of Pavement. Suitathe:Pavement Type flbxrb e: Pavement Pavement Design Fig 4.3. Form Showing Cost Compare Results Flexible pavement design: Flexible pavement design form can be activated by clicking "Flexible Pavement" sub menu of "Pavement Design" menu. User can design flexible pavement and save results also. Rigid pavement design: Rigid pavement design form can be activated by clicking "Rigid Pavement" sub menu of "Pavement Design" menu. User can design of rigid pavement and save results also. Help window is also available for temperature differential in India Overlay Design Overlay design by Benkelman beam method: Overlay Design by Benkelman Beam Method form can be activated by clicking "Benkelman Beam Method" sub menu of "Overlay Design" menu. User can design of overlay and save results also. Input can enter by keyboard or files. Help window is also available for vehicle damage factor.. 40

51 Overlay design by CBR method: Overlay Design by CBR Method form can be activated by clicking "CBR Method" sub menu of "Overlay Design" menu. User can design of overlay and save results also. Software provides results in tabular as well as graphical format. So user can understand easily Project Preparation Rate Analysis: Rate analysis form can be activated by clicking "Rate Analysis" menu. User can perform detailed rate analysis of different items and save it for a particular package number. Stored analysis for a package number can be retrieved and printed in the prescribed format Cercoreeero:Rolierrept,e1:ige:.::chi EI:lay :: :....,, State ANALYSIS OF: RATES Per STANDARO::DATA Book FOR ANALYSIS OF RATES FOR RUM: ROADS. Sot 2.004:)::. S I State ::BAREILLY District Code Pack ge::na UP Flood Neni Iiarizgarg.1arloput Road Uret of Iy 1 Material A 2 Material B... 3 Material C 15 Nos. TOTAL COST ry 'IUmt Rate is 23 Culy1. 15i Kg 'i ; Print Ekit. Fig 4.4. Analysis of Rates Form Cost estimate: cost estimate form can be activated by clicking "Cost Estimate" menu. User can calculate and save package number wise estimate of a particular district of a State. If cost estimate for given package number for a particular district of a state is already available, it will be displayed. 41

52 AigtftNNW - - COSP ESTI MATEFOR:EU RALFCADS::::' :;1111e UTTAR Pf1ADESH OPOR. UP ,!ri0 BAREILLY Mock inawnbquria F1 i.c1caqa UP - _ 511 :ii.ia1izgang Jadapur Road ata Asnaunt 1 Cement Cancaela 1:k5 with 90mm style 2 Eanh work for Embankment TOTAL 9 7 Cu.M Cu.M : Total :15.3H Fig 4.5. Cost Estimate Form Geometric Design Geometric design: To calculate superelevation click "Super Elevation" sub menu of the "Geometric Design" menu. It will display the form with fields to enter of design speed and radius of curve. By clicking "Compute" button user can get the superelevation in percent. ` 08.:99tnata: :o6inx[i Superelovation Design :INPUT:DATA: :Sala iar.1 l!a Plain and torrnin Hilly area hut not onnw hound Padu: of did,04 Fig 4.6. Super Elevation Form 42

53 4.3. CONVERSION OF CURVES AND TABLES INTO MATHEMATICAL FORMS IRC: SP: recommends table 3.2 for conversion of soaked CBR in k value. This table has been converted in the equations, which are as given below Table 4.2 Equations for k Value Corresponding to CBR Values S. Soaked CBR No. (% ) (x) Equations for k value (k Value Nimm2/mm x10-3) 1 2 to 5 k = ( *x * x * x * x ) / to 10 k = ( * x * x * x *x ) / (4.2) 3 10 to 20 k = ( * x * x ) / (4.3) 4 20 to 50 k = ( * x ) / (4.4) IRC: SP: recommends table 3.3 for calculating value coefficient C based on Bradbury's Chart based on L/1 and. W/1. This table has been converted in the equations, which are as given below: Table 4.3 Equations for Values of co-efficient 'C' based on Bradbury's Chart S. No. L/I and W/l (x) Equations for C value 1 1 to 3 C = * x * x to 10 C = * x * x * x * x (4.6) 3 More than 10 C = * x * x (4.7) IRC recommends the moisture correction factors (or seasonal correction factors) for different conditions of soil as shown in Figs These were converted into mathematical equations for different conditions of plasticity Index (PI), type of subgrade soil, annual rainfall and field moisture content. The equations are as given below. 43

54 Table 4.4 Equations for moisture correction factor Fig. Moisture Equation for moisture. No. Contents (%)(X) correction factor (Y) to 11 y = x x x x4...(4.8) to 4.55 y e-00663x...(4.9) 4.55 to 5.55 y = e x...(4.10) 5.55 to 7 y = e x...(4.11) 7 to 9 y = x x * 10-8x3...(4.12) more than 9 y = x x x x4...(4.13) to 22 y = x x x x x * 10-5x * 104)( * 10-9x8...(4.14) to 22 y = x x x x *10-5x *10-7x *10-9x to 20 y = x x x x x * 10-6 x * 10-8x7...(4.16) to 20 y = x x x x *10-6x5...(4.17) To calculate the thickness of Bituminous Macadam overlay (mm), design curves of WE: as shown in Fig3.7 are converted into mathematical equations for different values of characteristic deflection, (min) and the cumulative number of standard axles. For accuracy the curve for Ns = 0.1 is split in three ranges of characteristic deflection in mm, i.e., 3-3.4, 3.4-5, 5-6. So as to obtain three best fit equations which are as given below: 44

55 Table 4.5 Equations for overlay thickness Range of Equations for Ns characteristic deflection (X) overlay thickness to 3.4 y i = x...(4.18) 3.4 to 5 yi = x x x x4..(4.19) 5 to 6 yi= x x x3....(4.20) 0.5 < 2.2 y2= x-100x2 2.2 to 4.2 y2 = x x x x4...(4.22) 4.2 to 6 y2 = x x x x4...(4.23) where, yi= Overlay thickness at Ns 0.1 Y2 = Overlay thickness at Ns 0.5 The overlay thickness for Ns between 0.1 and 0.5 is calculated as y = yi+ (y2-y1)*log Ns-log 0.1)/ (log 0.5- log 0.1)... (4.24) Table 4.6 Equations for overlay thickness Ns 1.0 Range of characteristic deflection (X) < to 4.2 Equations for overlay thickness y3 = x x2 y3 = x x x x x5...(4.26) 4.2 to 6 y3 = x x x x4...(4.27) 2.0 < 1.8 y4 = x-225x2...(4.28) 45

56 1 8 to 6 Y4 = x x x x x x6...(4.29) The overlay thickness for Ns between 0.5 and 1.0 is calculated as y = y2+ (y3-y2)*(log Ns-log o.5)/ (log1.0-log0.5)... (4.30) The overlay thickness for Ns between 1.0 and 2.0 is calculated as y = y3+ (y4-y3)*(log Ns log 1.0)/ (log2.0-log1.0)... (4.31) where, y2 = overlay thickness at Ns 0.5 y3= overlay thickness at Ns 1.0 y4= overlay thickness at Ns 2.0 Ns = number of cumulative vehicles per day y = overlay thickness at given Ns Table 4.7 Equations for overlay thickness Range of Equations for Ns charactristic overlay thickness deflection (X) 5.0 < 1.2 y5 = x x2...(4.32) 1.2 to 4.0 y5 = x x x x4...(4.33) 4.0 to 6.0 y5 = x x x x4...(4.34) 10.0 <1.2 y6= x-587.5x2 (4.35) 1.2 to 4.0 Y6= * x * x2 46

57 x x * x x6....(4.36) 4.0 to 6.0 Y6 = x x x x x5...(4.37) The overlay thickness for Ns between 2.0 and 5.0 is calculated as y = y4+ (y5-y4)*log (Ns-log2.0)/ (log5.0-log2.0)... (4.38) The overlay thickness for Ns between 5.0 and 10.0 is calculated as y = Y5+ (y6-y4)*(log Ns-log5.0)/ (log10.0-log5.0)... (4.39) where, y4 = overlay thickness at Ns 2.0 y5 = overlay thickness at Ns 5.0 y6 = overlay thickness at Ns 10.0 Ns = number of cumulative vehicles per day y = overlay thickness at given Ns Table 4.8 Equations for overlay thickness Range of Equations for Ns charactristic overlay thickness deflection (X) 20 < 1.0 y7 = x2...(4.40) 1.0 to 3.2 y7 = x x x x4...(4.41) 3.2 to 6.0 y7 = x x x x x5...(4.42) 100 <0.625 y8 = x x2...(4.43) to 0.8 Y8 = x-400x2...(4.44) 47

58 0.8 to 2.8 y8= x x x x x5 2.8 to 6.0 Y8 = x x x x x x6...(4.46) The overlay thickness for Ns between 10.0 and 20.0 is calculated as y = y6+ (y7-y6)*(log Ns-log10.0)/ (log20.0-log10.0)... (4.47) The overlay thickness for Ns between 20.0 and is calculated as y = yrf (y8-y7)*(log Ns-log20.0)/ (log100.0-log20.0). (4.48) where, y6 = overlay thickness at Ns 10.0 y7 = overlay thickness at Ns 20.0 y8 = overlay thickness at Ns Ns = number of cumulative vehicles per day y = overlay thickness at given Ns The design curves of IRC-81, 1997 as depicted in Fig.3.7, are given up to Ns 100. One more curve for the value of Ns 200 was drawn and the equations for the overlay thickness are given in Table 4.9. Table 4.9 Equations for overlay thickness Range of Equations for Ns charactristic overlay thickness deflection (X) 200 < y9 = 1.503*( x x2)...(4.49) to 0.8 y9 = 1.43*( x-400x2)..(4.50) 48

59 0.8 to 0.9 y9 = *( x x x x x5)...(4.51) 0.9 to 1.1 y9 = 1.291*( x x x x x5)...(4.52) 1.1 to 2.8 y9 = *( x x x x x5)...(4.53) 2.8 to 6.0 y9 =1.031*( x x x x x x6)....(4.54) The overlay thickness for Ns between and is calculated as Y= Y8+ (Y9-Y8)*(log Ns-log100.0)/ (log200.0-log (4.55) where, ys = overlay thickness at Ns y9 = overlay thickness at Ns Ns = number of cumulative vehicles per day y = overlay thickness at given Ns 4.4. ADVANTAGE OF THE SOFTWARE This is user friendly software in which one can perform cost comparison, pavement design, overlay design, geometric design as superelevation, rate analysis, prepare estimate of road in the format prescribed in Operations Manual [22]. It saves time of user and provides efficient design solution SOURCE CODE OF THE SOFTWARE The source code of the software is given in the appendix. 49

60 CHAPTER 5 APPLICATION AND VERIFICATION OF THE SOFTWARE 5.1 GENERAL The software package developed in this thesis work is applicable for design of different types of pavement, flexible overlay over flexible pavement by different methods, rate analysis and cost estimation also. In this chapter, this software has been verified with different problem PAVEMENT DESIGN Flexible Pavement Design [27] The pavement design is performed using the software by taking the input data from Nabawgang block of Bareilly district in Uttar Pradesh, and design life 10 years + 1 year period is taken between last count and completion of construction. Annual rainfall is taken as 900 mm. Number of commercial vehicles per day at last count (P) = 79 Annual growth rate of commercial traffic (r) = 6 % Design life in years (x) = 10 years Motorized vehicle per day = 60 CBR value = 5.8 % Number of commercial vehicles per day for design, A = (1+01,+1 = 79 x ( )10+1 ti = CVPD 50

61 From CBR curves [9] for 150 CVPD and 5.8 % CBR, Total thickness = 330 mm From fig. 5.3 [9] Sub base = 175 mm Base Course = 150 mm Projected motorized vehicles/day = 60 x ( )10+1 = Type of surfacing as per Rural Roads Manual for 900 mm rainfall and 114 motorized vehicle per day = "Single Coat Surface Dressing" Table 5.1 Design Results for Flexible Pavement Result obtained by S. No. Parameters Manual Calculation Software 1. Design CVPD Traffic MVPD Sub base Thickness Base Thickness Single Coat Surface Single Coat Surface Surfacing Dressing Dressing Rigid Pavement Design [10] The pavement design is performed using the software by taking the input data from example of IRC: SP: , for Uttar Pradesh state. Design load = 51 kn Tyre pressure = 0.7 MPa Coefficient of thermal expansion of concrete (a) = 10x10-6 per C Modulus of Elasticity (E) = 3.0 x 104 MPa 51

62 Poisson's ratio (A.) = 0.15 Configuration of slab = 3.75 m x3.75 m Soaked CBR value = 4 % K value (k) = 35 x10-3 (N/mm2/mm) Characteristic compressive strength of concrete = 30 MPa Temperature differential = 12.5 C Table 5.2 Design Results for Rigid Pavement S. Result obtained by Parameters No. Manual Calculation Software 1. Trial Thickness (mm) Load stress in the edge region, (MPa) Temperature stress in the edge region, (MPa) Total Factor of safety Result Fail Fail Fail Fail Pass Pass 7. Load stress in the corner region, (MPa) Design slab thickness (mm) OVERLAY DESIGN Overlay Design by Benlielman Beam Method [161 The pavement design is performed using the software by taking the input data from report [16] for Purkaji - Laksar road. 52

63 Moisture content (%) = 4.2 Plastic index = less then 5 Rainfall = Low rainfall (less then 1300) Commercial vehicle per day = 786 Design life (years) = 10 Growth rate 7.5 Terrain = Rolling Vehicle damage factor = 3.5 Two lane road traffic in both directions Existing road surface = Thin surfacing of premixed carpet Type of road = major district road For two lane single carriageway roads initial traffic = 0.75x786 = Providing sub base of thickness 150 mm Table 5.3 Deflection values at typical section 1161 S. No. Initial Dial Gauge Reading Final Dial Gauge Reading Rebound Deflection (mm)

64 Ns- 365A[(1+ 1]F, Where, Ns = cumulative number of standard axles to be catered for in the design A = Corrected initial traffic r = Traffic growth factor x = Design period from present date F = Vehicle damage factor Ns 365 x590[( )1 1]x = msa 54

65 Table 5.4 Design Results for overlay by Benkelman Beam method Result obtained by S. No. Parameters Manual Calculation Software 1 Mean Deflection (mm) Standard Deviation (mm) Moisture correction factor Temperature correction Corrected Characteristic Deflection (mm) Overlay thickness (mm) in terms of BM Overlay Design by CBR Method [27] The overlay design is performed using the software by taking the input data from Nabawgang block of Bareilly district in Uttar Pradesh, and design life 10 years + 1 year period is taken between last count and completion of construction. Annual rainfall is taken as 900 mm. Existing crust thickness = 190 mm Width of existing road = 3.0 m Required width of new pavement = 3.75 Number of commercial vehicles per day at last count (P) = 79 Annual growth rate of commercial traffic (r) = 6 % Design life in years (x) = 10 years Motorized vehicle per day = 60 CBR value = 5.8 % Number of commercial vehicles per day for design, A = [P (1 r 55

66 = 79 x ( )10+1 = CVPD From CBR curves [9] for 150 CVPD and 5.8 % CBR, Total thickness = 330 mm Projected motorized vehicles/day = 60 x ( )10+1 = ,===, 114 Type of surfacing as per table 5.1 [9] for 900 mm rainfall and 114 motorized vehicle per day = "Single Coat Surface Dressing" ' r :',, :65*. Cross Sctional::VieW. of Road ss-stissiisv s,-szaat New Construction Existing Construction Fig 5.1. Form showing graphical view for overlay design by CBR method Table 5.5 Design Results for overlay by CBR method for existing Result obtained by S. Parameters Manual Calculation Software No. Calculated Proposed Calculated Proposed 1. Sub base Thickness Base G-2 Layer Thickness G-3 Layer Surfacing Single Coat Surface Single Coat Surface Dressing Dressing 56