Investigating the Effect of Speed on Critical Failure of Flexible Pavement with the Creep Compliance Function and Layer Theory Analysis

Speed of vehicles may affect performance and pavement distress. Two major factors of a flexible pavement distress due to traffic loading are fatigue cracking and rutting. Tensile strain below the surface layer and compressive strain on subgrade because of fatigue and rutting depend on various factors such as vehicles’ loading properties like speed and amount of passing load and contact pressure. In the present study, we studied the impact of the traffic speed on the maximum amount of tensile strain at the bottom of asphalt layer and the maximum compressive strain on the subgrade by changing the value of creep softening strain in a constant temperature of asphalt. Then, the impact of the strain obtained from changing the factor of vehicles’ traffic speed on pavement life was examined by using the elasticity modulus values resulted from the varying Creep compliance function. The pavement analysis was carried out by Ken-Pave layered software which enables us to make an elastic analysis of pavement under loading effect. The analyses were made in nine various sections with three different thicknesses of the asphalt layer on three different subgroups in five various speeds under standard axle loading traffic. The results indicated that the critical tensile strain of the asphalt layer decreased by speed increase. Therefore, fatigue, age was increased at high speeds because of the Creep compliance function reduction at these speeds. The effect of loading time on the speed of surface rutting growth was depended on the pavement geometry. The models’ analyses showed that the cracking decreased by 14% through 10 km/hr. increasing loading speed. In the statistical models with the decision tree and the neural network, the results were also discussed.