Niloufar Salehipour Bavarsad - M.S. in Road and Transportation Engineering, Payameh Nour University,Tehran, Ira
Parham Hayati - Ph.D. in Road and Transportation Engineering, Iran University of Science and Technology(IUST), Tehran, Iran
Shahin Shabani - Assistant Professor, Faculty Member of Payameh Nour University, Tehran, Ira

A flexible pavement should be designed based on an understanding of behavioral characteristics of materials used in different layers of the pavement. The performance and strength of materials in the sub-base and base layers in transferring traffic load directly depends on the behavior of their materials. In this paper, using Kenlayer, by analyzing the linear and nonlinear behavior of the sub-base and base layers, which were constructed on a compacted subgrade soil layer with invariant linear behavior and a viscoelastic asphalt layer, sensitivity of pavement design results was examined in the following three models in terms of pavement lifetime, damaging factors, and effects of layer thickness and material type (granular/fine-grained) to economies the plan: a sub-base layer with linear behavior and a base layer with nonlinear behavior (model 1); a subbase layer with nonlinear behavior and a base layer with linear behavior (mode 2); both layers with nonlinear behavior (model 3). The longest pavement lifetime was 24.24 years, which belonged to Model 2, while the shortest pavement lifetime was 5.1 years, which belonged to Model 3. Depending on the arrangement of material behavior and layer thickness, the pavement damaging factor varies between ratio of damage with horizontal tensile strain bottom the asphalt layer and vertical compressive strain top the subgrade soil. By a change in thickness of layers different results are obtained from models. With an increase in the sub-base thickness in Model 1 and Model 3, and a decrease in the base and sub-base thicknesses in Model 2 it is possible to improve the lifetime and costs of the plan. However, use of fine-grained materials in Model 3 has no effects.

flexible pavement, linear behavior, nonlinear, viscoelastic, Kenlayer software