Flexible Pavement Modelling using Kenlayer Dr. Amin Chegenizadeh* Research Fellow, Department of Civil Engineering, Curtin University of Technology, Kent Street, Bentley, Perth, Western Australia 6102, Australia

Corresponding author: [email protected]

Mahdi Keramatikerman PhD Candidate, Department of Civil Engineering, Curtin University of Technology, Kent Street, Bentley, Perth, Western Australia 6102, Australia

Prof. Hamid Nikraz Professor, Department of Civil Engineering, Curtin University

ABSTRACT Road is one of the main infrastructures that play a crucial role in economy development of countries. Pavement engineering is a key factor to design and construct optimum roads. Flexible pavement is one of the most applicable method in road construction that is made in a series of layers. The construction of this type of pavement is very fast and easy to repair and have a greater resistance in a wide range of temperature and additional layer always could be added at any time. There is a various modelling software to analyse flexible pavement structure. Kenlayer is one of the most effective application in analysing flexible pavement engineering. In this paper, the wellknown FEM package of kenlayer was used to evaluate flexible pavement deflection and stress distribution. In this research, the effect of different parameters such as layer moduli and poisson’s ratio were changed and the stress and deflection were compared.

KEYWORDS:

flexible pavement; kenlayer; deflection; stress distribution; layer moduli;

poisson’s ratio

INTRODUCTION In recent years, there has been an increasing interest in flexible pavement engineering studies. For instance, a study on interaction of the expansive soil with repetitive traffic load was carried out. The results showed that the strength of the expansive soil was decreased due to increase in water content of expansive soil [1]. In another study effect of industrial waste such as waste plastics and waste tyre rubber in clay/flyash as a subbase course investigated on a sandy subgrade and results indicated that clay reinforced waste tyre rubber provide the maximum carrying load capacity [2]. In a similar study in using waste materials stabilised with lime as subbase course, the variation of the rutting depth on subgrade layer was investigated the results showed that it leads to increase the lifetime of the asphalt pavement [3]. Degradation of a flexible pavement using CASTEM application as a finite element model by considering different parameters in rutting depth was investigated by another researchers [4]. In another case, a study of application on two types of industrial waste namely bagasse ash and lime sludge revealed that could increase strength of the subgrade and cost effective [5]. In a flexible

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pavement study strength property of the shale was increased using cement and lime [6]. In a numerical study, response of the asphalt cement pavement reinforced with geogrid was investigated and revealed that the highest value of the tension stress absorption increase when the geogrid located between asphalt and base layer [7]. An effective cost analysis of the flyash in constructing rural road revealed in a rigid pavement investigation [8]. Application finite element models in pavement engineering is very common. Kenlayar is a very popular application that has been used in many studies [9-16]. For instance, rutting and fatigue behaviour of the flexible pavement was performed using Kenlayer application [17]. In another study using Kenlayer in a flexible pavement, effect of surface layer thickness and modulus elasticity has been investigated [18]. This study aims to investigate effect of layer moduli and poisson’s ratio and the stress and deflection were compared using kenlayer application.

FLEXIBLE PAVEMENT Generally, pavement structures categorises in two group namely flexible and rigid pavement structures. The flexible pavements usually reflect the deformation to the underneath layers. This sort of pavements usually made with asphalt and does not have reinforcement materials. The design of the flexible pavement design usually stresses distribute based on their characteristics of each layers. The flexible strength of the flexible pavements is so negligible. The vertical stresses transfer to the underneath layers via contact points which are granules. The maximum compressive stresses directly apply to the surface under the wheel’s vehicle and is equal to contact pressure. The stresses decreases in lower layers due to distribution the loads to the larger area. Therefore, the flexible pavement is constructed in a series of layers which the top layer has the highest resistant for compressive stress. The inferior materials such as industrial waste could be applied in lower layers as they do not tolerate the compressive loads directly [19].

KENLAYER Kenlayer is a pavement engineering program which is used to analyse flexible pavement developed by Huang (1993) at university of Kentucky [20]. This program is designated to work in an elastic multilayer system under a circular loaded area. Kenlayer could be applied in multilayer systems under single or dual wheel while each layer have a different response like linear elastic, nonlinear elastic or viscoelastic. This application is designed to perform damage analysis too [20].

METHODOLOGY In this study to investigate effect of poisson’s ratio and pavement deflections flexible pavement parameters such as tolerance for integration, limit of integration cycles, number of period per year, number of load group and computing code were defined and input to the kenlayer application and analysis was performed. Figure 1 illustrates the flowchart of this study.

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Flexible Pavement input parameters are defined

Kenlayer is used a numerical tool to analyse the system

Effect of poison ratio and surface layer are investigated

Results are analysed

Figure 1: flowchart of the study In this study a three-layer flexible pavement has been considered. First layer is 5 cm, the second layer is 10 cm .Also three investigation points were determined to compare the results namely 0.00 cm, 6.00 cm and 14.00 cm. Poisson’s ratio of each layer are 0.5, 0.35, 0.3 and all interfaces has supposed fully bonded. Number of period per year and load group is equal to one. Tolerance for integration is 0.001 and limit of integration cycles is 100. The computing code is supposed as 5 and the radius of contact is 5 and contact pressure is equal to 80. The wheel spacing along x axis is 50 cm and along y axis is 14 cm. Refer to Figure 2 for response points.

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Figure 2: Schematic layering of pavement system with response points

RESULTS AND DISCUSSION Effect of surface layers Variation of the vertical displacement, vertical stress, major stress, minor stress and intermediate stress against changes in vertical coordination for ten different point. Table 1 shows the changes for a surface layer with 3 cm thickness. Variation of these parameters for surface layers with 5 cm and 7 cm thickness was shown in Table 2 and Table 3 respectively. According to Table 1, it could be seen that the rate of vertical displacement in all points is equal to 0.004 cm. The maximum acquired value for major stress amongst 0.00 vertical coordinate in Table 1 belongs to point number 1 and 3 which is equal to 1630.757 and 1623.591 kPa. The maximum rate of minor stress belongs to 0.00 vertical point for point number 1 and 3 which is equal to 43.213 kPa and 31.249. The maximum amounts of intermediate stresses belong to 0.00 vertical coordinate for point number 1 and 3 which is equal to 1503.622 kPa and 1512.714 kPa.

Table 1: Output for surface layer 3 cm Point No. 1

2 3

Vertical Coordinate 0.00 6.00 14.00 0.00 6.00 14.00 0.00

Vertical Vertical Major Minor Intermediate Displacement(cm) Stress(kPa) Stress(kPa) Stress(kPa) Stress(kPa) 0.004 80.000 1630.757 43.213 1503.622 0.004 2.883 2.994 0.207 0.347 0.004 2.145 2.210 0.174 0.264 0.004 80.000 1557.060 27.277 1440.490 0.004 2.962 3.026 0.260 0.351 0.004 2.197 2.247 0.178 0.266 0.004 0.000 1623.591 31.249 1512.714

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5

6

7

8

9

10

6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00

0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004

2471 2.971 2.214 0.000 2.688 2.184 0.000 2.766 2.233 0.000 2.790 2.251 0.000 2.411 2.133 0.000 2.471 2.175 0.000 2.492 2.190 0.000 2.304 2.100

3.021 2.258 1448.346 2.748 2.212 1498.540 2.784 2.246 1561.702 2.793 2.258 1238.820 2.465 2.153 1285.393 2.492 2.180 1282.277 2.502 2.191 1170.174 2.346 2.118

0.285 0.180 17.692 0.186 0.184 17.901 0.219 0.188 20.456 0.234 0.190 9.031 0.155 0.191 9.506 0.172 0.194 9.316 0.178 0.195 7.006 0.145 0.193

0.351 0.267 1357.358 0.491 0.350 1403.870 0.502 0.356 1460.661 0.505 0.358 1080.570 0.562 0.422 1108.579 0.578 0.431 1112.639 0.584 0.434 970.887 0.595 0.451

According to Table 2, the acquired vertical displacement for surface layer with 5 cm thickness is equal to 0.003 cm. The maximum value for vertical stress is 80 kPa and belongs to 0.00 vertical coordinate in point 1 and 2. The recorded maximum and minimum values for major stress amongst 0.00 vertical coordinate for 10 different points is equal to 882.663 kPa and 700.678 kPa. The values for vertical coordinate at 6 and 14 cm are much lesser than the values at 0.00 vertical coordinate.

Table 2: Output for surface layer 5 cm Point No. 1

2

3

4

5

Vertical Coordinate 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00

Vertical Displacement(cm) 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003

Vertical Stress(kPa) 80.000 1.378 1.099 80.000 1.397 1.115 0.000 1.398 1.127 0.000 1.320 1.129 0.000 1.343 1.144

Major Stress(kPa) 845.405 1.419 1.117 882.663 1.425 1.130 843.794 1.423 1.140 783.760 1.336 1.136 788.030 1.347 1.147

Minor Stress(kPa) 23.826 0.261 -0.434 25.736 0.283 -0.452 18.461 0.296 -0.457 12.301 0.269 -0.434 11.601 0.282 -0.453

Intermediate Stress(kPa) 814.204 0.294 -0.316 854.735 0.294 -0.328 812.858 0.300 -0.330 743.383 0.361 -0.285 740.769 0.365 -0.292

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7

8

9

10

0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00

0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003

2472 0.000 1.348 1.149 0.000 1.246 1.123 0.000 1.265 1.136 0.000 1.272 1.141 0.000 1.220 1.118

838.169 1.349 1.151 751.991 1.259 1.127 771.667 1.269 1.138 778.809 1.272 1.141 700.678 1.232 1.122

15.377 0.287 -0.460 8.762 0.266 -0.420 9.179 0.272 -0.438 9.316 0.275 -0.445 6.312 0.265 -0.412

787.591 0.366 -0.295 682.125 0.384 -0.227 695.648 0.391 -0.230 700.671 0.393 -0.232 641.069 0.391 -0.199

Similar to two previous tables, Table number 3 with 7 cm surface layer have an almost similar trend. Vertical displacement for this tested specimen is equal to 0.002 cm. Major stress for 0.00 vertical coordinate amongst 10 different points is equal to 546.822 kPa and belongs to point number 3. The maximum recorded values for intermediate stress values belongs to 0.00 vertical coordinate at point number 3 that is equal to 526.768 kPa.

Table 3: Output for surface layer 7 cm Point No. 1

2

3

4

5

6

7 8

Vertical Coordinate 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00

Vertical Vertical Major Minor Intermediate Displacement(cm) Stress(kPa) Stress(kPa) Stress(kPa) Stress(kPa) 0.002 80.000 505.552 13.687 485.548 0.002 5.901 6.081 -396.850 -378.960 0.002 0.665 0.675 -0.114 -0.070 0.002 80.000 507.432 13.249 484.876 0.002 4.409 4.468 -398.682 -385.880 0.002 0.673 0.681 -0.119 -0.073 0.002 0.000 546.822 18.461 526.768 0.002 1.619 1.648 -392.617 -386.589 0.002 0.679 0.686 -0.123 -0.077 0.002 0.000 498.201 11.012 481.010 0.002 0.775 1.407 -363.845 -322.082 0.002 0.682 0.686 -0.116 -0.058 0.002 0.000 487.200 9.417 467.623 0.002 0.648 1.120 -372.136 -329.120 0.002 0.690 0.692 -0.121 -0.060 0.002 0.000 489.065 8.925 469.876 0.002 0.545 0.918 -372.857 -330.994 0.002 0.693 0.694 -0.123 -0.060 0.002 0.000 468.585 6.717 443.382 0.002 0.695 0.832 -330.531 -272.640 0.002 0.678 0.681 -0.112 -0.039 0.002 0.000 478.725 7.029 451.398 0.002 0.704 0.817 -339.523 -276.505

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14.00 0.00 6.00 14.00 0.00 6.00 14.00

0.002 0.002 0.002 0.002 0.002 0.002 0.002

2473 0.684 0.000 0.708 0.686 0.000 0.687 0.676

0.685 482.423 0.812 0.686 474.500 0.722 0.678

-0.117 7.131 -342.764 -0.119 6.312 -319.828 -0.110

-0.039 454.360 -277.978 -0.040 441.606 -257.331 -0.030

Effect of Poisson’s ratio Passion ratio is an important parameter in analysis of the elasticity of the materials in pavement engineering. The Poisson’s ratio is the ratio of transverse to longitudinal strains of a loaded specimen. The value for firmer materials is lower in compare with softer materials. Table 4, 5 and 6 illustrate the variation of the Poisson’s ratio with vertical displacement, vertical stress. According to Table 4, the value of vertical displacement for a surface layer with a Poisson’s ratio of 0.5 (surface layer thickness = 5cm) is calculated as 0.003cm. The maximum rate of vertical stress for 0.00 vertical coordinate amongst 10 different points is equal to 80 kPa and belongs to point number 1 and 2. The maximum value for major stress is 882.663 kPa and belongs to 0.00 cm vertical coordinate at point number 2. The maximum value for minor stress and intermediate stress at the same vertical coordinate and at point number two is equal to 25.736 kPa and 854.735 kPa respectively.

Table 4: Output for Poisson’s ratio changes (0. 5 for surface layer) Point No. 1

2

3

4

5

6

7

8

Vertical Coordinate 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00

Vertical Vertical Major Minor Intermediate Displacement(cm) Stress(kPa) Stress(kPa) Stress(kPa) Stress(kPa) 0.003 80.000 845.405 23.826 814.204 0.003 1.378 1.419 0.261 0.294 0.003 1.099 1.117 -0.434 -0.316 0.003 80.000 882.663 25.736 854.735 0.003 1.397 1.425 0.283 0.294 0.003 1.115 1.130 -0.452 -0.328 0.003 0.000 843.794 18.461 812.858 0.003 1.398 1.423 0.296 0.300 0.003 1.127 1.140 -0.457 -0.330 0.003 0.000 783.760 12.301 743.383 0.003 1.320 1.336 0.269 0.361 0.003 1.129 1.136 -0.434 -0.285 0.003 0.000 788.030 11.601 740.769 0.003 1.343 1.347 0.282 0.365 0.003 1.144 1.147 -0.453 -0.292 0.003 0.000 838.169 15.377 787.591 0.003 1.348 1.349 0.287 0.366 0.003 1.149 1.151 -0.460 -0.295 0.003 0.000 751.991 8.762 682.125 0.003 1.246 1.259 0.266 0.384 0.003 1.123 1.127 -0.420 -0.227 0.003 0.000 771.667 9.179 695.648 0.003 1.265 1.269 0.272 0.391 0.003 1.136 1.138 -0.438 -0.230

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0.00 6.00 14.00 0.00 6.00 14.00

0.003 0.003 0.003 0.003 0.003 0.003

2474 0.000 1.272 1.141 0.000 1.220 1.118

778.809 1.272 1.141 700.678 1.232 1.122

9.316 0.275 -0.445 6.312 0.265 -0.412

700.671 0.393 -0.232 641.069 0.391 -0.199

Table 5 illustrates the variation of the vertical displacement, vertical stresses for Poisson ratio of 0.45. Vertical displacement value for a Poisson’s ratio with rate for 0.45 is equal to 0.003cm. The maximum values for major, minor and intermediate stresses belong to 6.00 com vertical coordinates point number 2 amongst 10 different points which are equal to 768.591 kPa, 25.736 kPa and 734.594 kPa.

Table 5: Output for Poisson’s ratio changes (0.45 for surface layer) Point No. 1

2

3

4

5

6

7

8

9

10

Vertical Coordinate 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00

Vertical Vertical Major Minor Intermediate Displacement(cm) Stress(kPa) Stress(kPa) Stress(kPa) Stress(kPa) 0.003 80.000 736.203 23.826 697.635 0.003 1.510 1.556 0.273 0.310 0.003 1.190 1.210 -0.498 -0.364 0.003 80.000 768.591 25.736 734.594 0.003 1.531 1.562 0.298 0.311 0.003 1.208 1.224 -0.520 -0.378 0.003 0.000 733.966 18.461 695.963 0.003 1.530 1.558 0.312 0.317 0.003 1.220 1.235 -0.525 -0.381 0.003 0.000 682.072 12.301 631.048 0.003 1.437 1.456 0.280 0.386 0.003 1.220 1.228 -0.498 -0.327 0.003 0.000 687.167 11.601 627.287 0.003 1.463 1.468 0.295 0.391 0.003 1.237 1.241 -0.521 -0.336 0.003 0.000 732.697 15.377 668.480 0.003 1.470 1.470 0.301 0.391 0.003 1.243 1.246 -0.529 -0.340 0.003 0.000 659.430 8.762 569.513 0.003 1.349 1.365 0.276 0.413 0.003 1.212 1.217 -0.482 -0.259 0.003 0.000 678.092 9.179 580.254 0.003 1.370 1.375 0.283 0.420 0.003 1.227 1.229 -0.503 -0.263 0.003 0.000 684.840 9.316 584.286 0.003 1.378 1.379 0.286 0.423 0.003 1.233 1.233 -0.510 -0.265 0.003 0.000 611.153 6.312 534.705 0.003 1.318 1.332 0.275 0.421 0.003 1.206 1.210 -0.472 -0.226

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Table 6 illustrates the variation of the vertical stress, major, minor and intermediate against various vertical coordinates at different point numbers for a Poisson’s ratio of 0.35. It could be seen from the below table that the maximum rate of vertical stress is 80 kPa for 0.00 vertical coordinate and at point number of 1 and 2. The maximum rate of major, minor and intermediate stresses which is located at 0.00 vertical coordinate at the first point are equal to 849.123 kPa, 111.578 kPa and 799.503 kPa respectively.

Table 6: Output for Poisson’s ratio changes (0.35 for surface layer) Point No. 1

2

3

4

5

6

7

8

9

10

Vertical Coordinate

Vertical Displacement(cm)

Vertical Stress(kPa)

Major Stress(kPa)

Minor Stress(kPa)

Intermediate Stress(kPa)

0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00 0.00 6.00 14.00

0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003

80.000 1.510 1.190 80.000 1.531 1.208 0.000 1.530 1.220 0.000 1.437 1.220 0.000 1.463 1.237 0.000 1.470 1.243 0.000 1.349 1.212 0.000 1.370 1.227 0.000 1.378 1.233 0.000 1.318 1.206

849.123 1.556 1.210 814.648 1.562 1.224 809.740 1.558 1.234 704.967 1.456 1.228 710.121 1.468 1.241 711.800 1.470 1.246 617.736 1.364 1.217 643.773 1.375 1.229 656.122 1.379 1.233 600.106 1.332 1.210

111.578 0.273 -0.498 63.983 0.298 -0.520 45.555 0.312 -0.525 13.456 0.280 -0.498 -5.101 0.295 -0.521 -5.915 0.301 -0.529 -3.545 0.276 -0.482 -0.848 0.283 -0.503 3.280 0.286 -0.510 0.972 0.275 -0.472

799.503 0.310 -0.364 780.707 0.311 -0.378 764.674 0.317 -0.381 577.299 0.387 -0.327 569.054 0.391 -0.336 575.004 0.391 -0.339 420.810 0.413 -0.259 430.069 0.420 -0.263 438.271 0.423 -0.265 390.462 0.421 -0.226

COMPARISON SELECTED POINTS Figure 3 compares the major, minor and intermediate stresses for 0.00 vertical coordinate at point number one. It could be clearly seen that the maximum values belong to major stress and intermediate stress of the specimen with 3 cm thickness with 1630.757 kPa and 1503.622 kPa respectively and the lowest values belong to the specimen with 7 cm thickness with 505.552 kPa and 485.548 kPa for major and intermediate stresses respectively. The rest of specimens have stresses in range of 690.00 to 850.00. The minor stresses have much lower value in compare with major and intermediate stresses. The highest value belongs to the Poisson’s ratio of 0.35 with 111.578 kPa and the lowest belong to specimen with 7 cm thickness with a minor stress of 13.687 kPa.

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1800 1630.757 1600

1503.622

1400

1200

1000 845.405

845.405

814.204

849.123

814.204

800

736.203

600

505.552

799.503

697.635

485.548

400

200

111.578 43.213

23.826

Thickness 3 cm

Thickness 5 cm

13.687

23.826

23.826

Thickness 7 cm

PR 0.5

PR 0.45

0 Major Stress

Minor Stress

PR 0.35

Intermediate Stress

Figure 3: Comparison of the major, minor and intermediate stresses for 0.00 vertical coordinate at point number one Figure 4 illustrates the major, intermediate and the minor stresses of the 0.00 vertical coordinate at point number six. Similar to Figure 2, the maximum values of major and intermediate stresses belong to the specimen with 3 cm thickness which 1561.702 kPa and 1460.661 kPa respectively and the lowest values belong to specimen with 7 cm thickness with 489.065 kPa and 469.876 kPa respectively.

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1800

1600

1561.702 1460.661

1400

1200

1000 838.169

838.169 787.591

800

787.591 732.697 668.48

711.8 575.004

600 489.065

469.876

400

200 20.456

15.377

8.925

15.377

15.377

Thickness 3 cm

Thickness 5 cm

Thickness 7 cm

PR 0.5

PR 0.45

0 -5.915 PR 0.35

-200 Major Stress

Minor Stress

Intermediate Stress

Figure 4: Comparison of the major, minor and intermediate stresses for 0.00 vertical coordinate at point number six

CONCLUSION Road is one of the most important infrastructures in each country. Pavement engineering is a crucial part of road design and construction that directly deals with efficiency and cost effectiveness of these vital veins. In this study, Kenlayer as a finite element application was used to examine the effect of surface layer change and position ratio in the displacement and stress distribution of a given pavement system. The results were compared and analysed. According to analysis, the rate of vertical stresses for 0.00 vertical coordinates at all ten points have been the same. Generally, the results showed that the values of major and intermediate stresses at 0.00 vertical coordinates for specimens with 3 cm thickness have the highest values and the specimens with 7 cm thickness showed the lowest values of the major and intermediate stresses. Acquired rates of minor stresses showed much lesser values in compare with major and intermediate stresses.

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[3] Khabiri, M. M., “The Effect of Stabilized Subbase Containing Waste Construction Materials on Reduction of Pavement Rutting Depth.” Electronic Journal of Geotechnical Engineering, 2010(15): 1211-1219. Available at ejge.com. [4] Tchemou, G., et al., “Prediction of Flexible Pavement Degradation: Application to Rutting in Cameroonian Highways.” Electronic Journal of Geotechnical Engineering, 2011(16): 13011319. Available at ejge.com. [5] Sabat, A.K., “Utilization of bagasse ash and lime sludge for construction of flexible pavements in expansive soil areas.” Electronic Journal of Geotechnical Engineering, 2012 (17): 10371046. Available at ejge.com. [6] Joel, M. and I. Agbede, “Cement stabilization of igumale shale lime admixture for use as flexible pavement construction material.” Electronic Journal of Geotechnical Engineering, 2010 (15): 1661-1673. Available at ejge.com. [7] Moayedi, H., et al., “Effect of geogrid reinforcement location in paved road improvement.” Electronic Journal of Geotechnical Engineering, 2009(14). Available at ejge.com. [8] Basak, S., A.K. Bhattacharya, and S.L. Paira, “Utilization of fly ash in rural road construction in India and its cost effectiveness.” Electronic Journal of Geotechnical Engineering, 2004. 436. Available at ejge.com. [9] Ziari, H. and M.M. Khabiri, Interface condition influence on prediction of flexible pavement life. Journal of Civil Engineering and Management, 2007. 13(1): p. 71-76. [10] Loulizi, A., et al., Measurement of vertical compressive stress pulse in flexible pavements: representation for dynamic loading tests. Transportation Research Record: Journal of the Transportation Research Board, 2002(1816): p. 125-136. [11] Gedafa, D.S., Comparison of flexible pavement performance using kenlayer and hdm-4. Midwest Transportation Consortium, Ames, Iowa, 2006. [12] Ameri, M. and A. Khavandi, Development of Mechanistic-Empirical Flexible Pavement Design in Iran. Journal of Applied Sciences, 2009. 9(2): p. 354-359. [13] Wang, J.-N., C.-K. Yang, and T.-Y. Luo, Mechanistic analysis of asphalt pavements, using superpave shear tester and Hamburg wheel-tracking device. Transportation Research Record: Journal of the Transportation Research Board, 2001(1767): p. 102-110. [14] Parker, N.A. and S. Hussain Ph D. Pavement damage and road pricing. In Transportation Research Board 85th Annual Meeting. 2006. [15] Zuo, G., R. Meier, and E. Drumm, Effect of temperature averaging on predicted pavement life. Transportation Research Record: Journal of the Transportation Research Board, 2002(1809): p. 119-125. [16] Ayan, V., Assessment of recycled aggregates for use in unbound subbase of highway pavement. 2011, Kingston University. [17] Abdel-Motaleb, M., Flexible pavement components for optimum performance in rutting and fatigue. Zagazig Univ J, 2009. [18] Srikanth, M.R., Study on Effect of Surface Course Thickness and Modulus of Elasticity on Performance of Flexible Pavement using a Software Tool. International Journal of Engineering Research & Technology, 2015. Volume. 4 (Issue. 08, August - 2015).

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