Traffic Analysis and Design of Flexible Pavement With Cemented Base and Subbase

Traffic Analysis and Design of Flexible Pavement With Cemented Base and Subbase

Ravinder Kumar

M-TECH Scholar NIT Kurukshetra, Haryana

Dr. S.N. Sachdeva,

Professor Civil Engineering Department NIT Kurukshetra, Haryana.

Abstract: The National Highways are the backbone of the road infrastructure and the major roads in India. They carry most of Indias freight and passenger traffic. National highways (NH) presently totalling to a length of about 77000 km, carry nearly 40 per cent of the traffic, and are the most important category of roads. Flexible pavements are those, which on the whole have low or negligible flexural strength and are rather flexible in their structural action under the load. The service life of a flexible pavement is typically designed in the range of 15 to 20 years. Required thicknesses of each layer of a flexible pavement varies widely depending on the materials used, magnitude and number of repetitions of traffic loads, environmental conditions and the desired service life of the pavement. The latest design method of IRC: 37- 2012 is mechanistic approach of design and incorporates the use of non conventional kinds of materials also in the base and sub-base. The stretch of NH-1 between Karnal to Kurukshetra is taken for the study. The required data are collected from NHAI office Ambala which include previous years traffic data, CBR value and VDF. Using the data, the cumulative design traffic in standard axles is calculated for the design life. The traffic data have been analyzed to find annual and monthly variation of traffic. Finally using the cumulative standard axles and effective CBR value, the pavement has been designed for period of 15 years, using IRC 37:2012 guidelines of flexible pavement design.

Keywords: Design; Flexible pavement; traffic; standard axles; thickness of pavement; CBR.

1. INTRODUCTION

   Flexible pavements are so named because the total pavement structure deflects, or flexes, under loading. Each layer receives the loads from the above layer, spreads them out, and then passes on these loads to the next layer below. The purpose of design is to provide a pavement structure which is capable of withstanding the traffic loads which would be coming onto it during the design life of a pavement. The design involves determining the thickness

   of component layers based on the strength characteristics of the pavement materials. India is now a total about 33 lakh km is colossal. It requires not only adequate resources but also proper planning and innovative way of maintenance.

   National highways (NH) presently totalling to a length of about 77000 km, carry nearly 40 per cent of the traffic, and are the most important category of roads. NH 1 is a National Highway in Northern India that links the national capital New Delhi to the town of Attari in Punjab near the IndiaPakistan border. This was a part of Grand Trunk Road of Sher Shah Suri that ran from Lahore to Bengal, built on earlier roads that existed from time immemorial. This is one of the longest and oldest highways of India. The NH 1 passes through Amritsar, Jalandhar, Phagwara, Ludhiana, Rajpura, Ambala, Kurukshetra, Karnal, Panipat, Sonepat and Delhi. It runs for a distance of 456 km. The DelhiLahore Bus travels on NH 1 in India. It does not have a uniform laning. From the Wagah Border (between India and Pakistan) through Amritsar up to Jalandhar it is 4-laned. From Jalandhar up to the border between Haryana's Sonepat and the national capital Delhi, it is 6- laned. Its entire stretch in Delhi is 8-laned. This stretch comes under the northern highway i.e. Karnal to Kurukshetra (NH1), data available from Karnal toll plaza. Road Distance or driving distance from Karnal to Kurukshetra is 38 kms. The total travel time is approximately 35min(s); which may vary depending upon the road and traffic conditions.

2. OBJECTIVES OF STUDY

   1. Collecting traffic data for the study stretch which would be used in the design

   2. Analyzing the data to extract meaningful estimates of yearly and monthly variation of traffic.

   3. Finding pavement composition from available data based on the IRC: 37-2012 guidelines [1].

3. METHODOLOGY

   Indian Roads Congress Method: Indian Roads Congress Method is based on an empirical method where the thickness value of a pavement used was read from the CBR value of the sub-grade. From the design chart the total pavement thickness could be read for a given CBR value and cumulative standard axle load. The design procedure of the pavements based IRC: 37-2012 guidelines [1].

   1. Selection of a trial pavement including the number of layers and thicknesses of all layers overlying the sub grade.

   2. Selection of design loading (traffic) and determination of vertical stress (i.e., tire contact pressure) and radius of the tire contact area.

   3. Determination of the elastic parameters of asphalt which include flexural modulus and Poisson's ratio.

   4. Determination of the cemented base and cemented sub base elastic parameters of the sub grade elastic modulus and Poisson's ratio.

   5. Determination of the elastic parameters of the granular sub-layer as mentioned in step (IV) and which include elastic modulus and Poisson's ratio.

   6. Using the IITPAVE software to calculate the Actual Horizontal Tensile Strain in Bituminous layer and Actual Vertical Compressive Strain on sub-grade.

4. TRAFFIC GROWTH RATE (r)

   As per Clause 5.5.4 of 4 laning Manual of Specifications and Standards IRC SP 84 2009 (Published by Planning Commission of India) [2], it is said to adopt a realistic value of growth rate for pavement design provided that the annual growth rate of commercial vehicles shall not be less than 5%. Considering this clause 5% growth rate is adopted for calculating the design traffic as given in [1].

5. VEHICLE DAMAGE FACTORS (F)

The Vehicle Damage Factor values for the commercial vehicles like LCVs, Bus, 2-Axle trucks, 3-Axle trucks and Multi Axle Vehicles (MAV) have been mentioned in Table

1. The VDF values for the Panipat-Jalandhar route have been adopted for the calculations in the study according to available NHAI data [3].

   Table 1 Vehicle Damage Factors for different vehicle types

   Vehicle Type	Vehicles Damage Factors
   	Panipat- Jalandhar	Jalandhar-Panipat
   Bus	0.975	1.12
   LCVs	0.480	0.31
   2-Axle Trucks	4.48	3.50
   3-Axle Trucks	5.97	5.80
   MAV	8.11	2.67

   1. LANE DISTRIBUTION (D)

      The Lane distribution is a realistic assessment of distribution of commercial traffic by direction as it affects

      the total equivalent standard axle load. It is taken as 0.45 from clause 4.5.1 of IRC 37-2012.

   2. TRAFFIC VOLUME

      Yearly Variation in Commercial Traffic

      400000

      350000

      300000

      250000

      200000

      150000

      No. of Vehicles

      The previous year traffic data for Karnal Toll Plaza was collected from the NHAI office. This data was analyzed and following observations were made. Figure 1 shows the yearly variation in commercial traffic. The figure 1 shows that the minimum commercial raffic was observed in the year 2009-2010 and the maximum in the year 2010-2011.

      Years

      no. of

      vehicles

      100000

      50000

      0

      Figure 1 Yearly variation of commercial vehicles (May Apr)

      No. of Vehicles

      Figure 2 shows the yearly variation in LCV. The figure 2 shows that the minimum LCV were observed in the year 2009-2010 and the maximum in the year 2010-2011.

      Yearly variation in LCV

      1400000

      1200000

      1000000

      800000

      600000

      400000

      200000

      0

      no. of

      vehicles

      Years

      Figure 2 Yearly variation of LCVs (May – Apr)

      Figure 3 shows the yearly variation in Truck/Bus. The figure 3 shows that the minimum Truck/Bus were observed in the year 2009-2010 and the maximum in the year 2010- 2011.

      1800000

      1600000

      1400000

      1200000

      1000000

      800000

      600000

      400000

      200000

      0

      Yearly Variations in Truck/Bus

      Figure 6 shows the monthly variation in LCV. The figure 6 shows that the minimum LCV were observed in the month of February and the maximum in December.

      No. of Vehicles

      Monthly Variation in LCV

      no. of

      vehicles

      Years

      Figure 3 Yearly variation of truck (May – Apr)

      Figure 4 shows the yearly variation in Heavy Construction Machine/Earth Moving Equipment. The figure 4 shows that the minimum HCM/EME was observed in the year 2009- 2010 and the maximum in the year 2012-2013.

      120000

      No. of Vehicles

      115000

      110000

      105000

      100000

      95000

      90000

      85000

      Months

      no. of vehi

      Yearly Variation in HCM/EME

      Figure 6 Monthly variation of Jeep/Car

      1000000

      800000

      600000

      400000

      Figure 7 shows the monthly variation in Truck/Bus. The figure 7 shows that the minimum Truck/Bus were observed in the month of February and the maximum in December.

      no. 0f

      vehicles

      No. of Vehicles

      Monthly variation in Trucks and Buses

      200000

      0

      Years

      Figure 4 Yearly variation of HCM/EME (May – Apr)

      Figure 5 shows the yearly variation in Car. The figure 5 shows that the minimum Cars were observed in the year 2009-2010 and the maximum in the year 2012-2013.

      140000

      120000

      100000

      80000

      60000

      40000

      20000

      0

      no. of vehicles

      Yearly Variation in Car

      8000000

      6000000

      4000000 no of

      2000000 vehicles

      0

      Years

      No of Vehicles

      Figure 7 Monthly variation of Truck/Bus

      Figure 8 shows the monthly variation in Car. The figure 8 shows that the minimum Car was observed in the month of

      September and the maximum in June.

      Figure 5 Yearly variation of Jeep/Car (May – Apr)

      Monthly Variation in cars

      70000

      60000

      50000

      40000

      30000

      20000

      10000

      0

      no. of

      vehicles

      Figure 8 Monthly variation of Car

   3. DAILY TRAFFIC VOLUME

      The initial traffic survey data was available for the year 2014. Estimate of initial daily average traffic flow for any road should normally be based on at least 7 days, 24 hour classified traffic counts. Table 2 shows the daily traffic count observed at the Karnal Toll plaza in the year 2014. For this study only the counts for bus, Trucks (2 and 3 axles) and MAV were considered.

      Table 2: Daily Traffic Volume Counts observed at Karnal Toll Plaza (Km 98)

      Year	Bus		Truck
      	Mini	Sta nda rd	LC V	2-A	3-A	M A V
      2014	380	257 0	457 0	432 0	1970	73 0

      1. Design Traffic Cumulative Million Standard Axles

         Based on the above said parameters the design traffic in terms of CMSA is computed for a design period (n) of 15 years.

         N = 365× (1+) 1 × × × (1)

         D: Lane distribution factor.

         F: Vehicle Damage Factor (VDF). n: Design life in years.

         r: Annual growth rate of commercial vehicles (for 5% annual growth rate r=0.05).

         Table 3 Design Traffic MSA

         Location	Design Traffic for 15 Years
         Karnal Toll Plaza (KM 98)	149.23 (Says 150)

      2. Design Thickness of Conventional Layer

         A sub grade effective CBR of 7.3% is adopted for the design. If soil having an effective CBR of 7.3% is not available, suitable stabilization techniques shall be adopted to improve the sub-grade strength. Crust Composition is obtained from Pavement Design Catalogue of IRC: 37- 2012 for 7.3% CBR and for Design Traffic in MSA. Crust Composition is given in Table 4.

         Table 4 Crust Composition for Conventional materials

         Design Period	15
         Effective CBR	7.3
         BC (mm)	50
         DBM (mm)	140
         WMM (mm)	250
         GSB (mm)	230
         TOTAL (mm)	670

      3. Design Thickness of Non-Conventional Layer

         In place of conventional layers of GSB and WBM/WMM in sub-base and base course of the pavement, cement treated base and cement treated sub-base layers can also be provided. A crack relief layer of wet mix macadam of thickness 100 mm sandwiched between the bituminous layer and treated layer is much more effective in arresting the propagation of cracks from the cementitious base to the bituminous layer, given in Table 5.

         Table 5 Crust Composition for Non-conventional materials

         Design Period	15
         Effective CBR	7.3
         BC (mm)	50
         DBM (mm)	50
         Aggregate Inter-layer (mm)	100
         CT-Base (mm)	120
         CT-Sub-Base (mm)	250
         Total (mm)	570

         Where,

         N: The cumulative number of standard axles to be catered for in the design in terms of MSA A: Initial traffic in the year of completion of construction in terms of number of commercial vehicles per day.

      4. Cross Check for Safety

      The actual values of strain as calculated using IITPAVE software. The comparison of these values is tabulated below:

      Table 6 Horizontal and Vertical Strains

      Location/Type of Strain	Allowable Strain	Actual Strain From IITPAVE	Remarks
      Horizontal Tensile Strain in Bituminous Layer	187.78*10- 06	132.6*10- 06	Safe
      Vertical Compressive Strain on sub- grade	291.70*10- 06	222.1*10- 06	Safe
      Tensile Strain in Cementitious Layer	57.12*10- 06	54.0*10- 06	Safe

   4. CONCLUSION

      We can conclude that the design of Flexible Pavement using non-conventional layer requires less thickness of pavement and less quantity of bitumen (which is one of costlier material of pavements, saving of bitumen layer up to 47 %) which leads to less usage of material specially the aggregate which is good for environmental point of view. Saving o bitumen and more usage of cement is a better practice as cement is abundantly available which bitumen depends on the imports. The traffic and sub-grade soil characteristics are necessary in order to design a pavement. The IRC method of design can be used to find the total pavement thickness due to its simple approach. A decline in the yearly variation of commercial vehicles like bus, truck and HCM/EME was observed from the data analysis of traffic volume data. An increase in the yearly volume of cars was also observed from the analysis. The volume of commercial traffic has decreased in 2013 as compared to previous years probably due to imposition of heavy toll tax and construction work of widening of road from 4 to 6 lanes going on the road.

   5. REFERENCES

1. IRC: 37-2012 Guidelines for the Design of Flexible Pavements, New Delhi, 2012.

2. IRC: SP: 84 Manual of specifications & standards for Four Laning of Highways through Public Private Partnership New Delhi, 2009.

3. National Highways Authority of India, 2007. Feasibility for 6- laning of NH-1 from Panipat Jalandhar in the State of Haryana/Punjab on DBFO basis. New Delhi.