Numerical Simulation Of Failure Process Of Transversely Isotropic Layered Pavement Structure By Damage Theory

In recent years, the highway develops rapidly in China. Because of the speed ofvehicles traveling on the highway and heavy traffic, compared with ordinary road, therequirements of highway are higher on the pavement structure. The settlement of the roadis the main controlling factor of the pavement structure, the settlement of pavement undertraffic loads is the problem which is concerned about all along.The subgrade is an important part of the road projects and the main body ofload-bearing, suffering the weight of pavement and vehicle load coming from pavement.Subgrade will produce excessive residual deformation under the traffic loads coming frompavement, performing as larger settlement, differential settlement and cracking, andgradually reflect to pavement. Numerous studies indicate that, the process of traffic loadaccompanies with the occurrence in damage. Damage mechanics has been widely used ingeotechnical engineering. Relation of elastic-plastic of the subgrade which considering thedamage can better reflect its mechanical properties. The large number of experimentalstudies have shown that the subgrade perform as significantly transversely isotropicproperties, Therefor, this paper also considers the transversely isotropic properties ofsubgrade.Based on the results of existing studies, combining elastic damage theory with thefinite element method, a three dimension simulation model of asphalt pavement structure isestablished. Applying transversely isotropic elastic damage on its subgrade, displacementand stress of pavement structure under static load and moving load is analyzed. And theresults are compared with the one which is not considering the damage of subgrade. The chief research is summarized as follows:1. Asphalt Pavement Structure has been selected as the research object and uniformmoving load is used to simulate moving vehicle load. Considering the accuracy and cost ofnumerical calculation, the impact rang of vehicle load is determined and elastic damageconstitutive model of subgrade is established. Time history curves of stress anddisplacement on case of considering damage or not is obtained.2. The vertical displacement at different locations along the depth direction of thepavement structure is calculated in the case of using isotropic constitutive model,transversely isotropic constitutive model of the subgrade and changing transverselyisotropic coefficient of subgrade. The effect of transversely isotropic properties of subgradeon critical design indexes of pavement structure is analyzed.。3. The existing asphalt pavement design standard regards displacement and stress asdesign indexes. So the settlement of surface course, tensile stress of the bottom of basecourse and shear stress of surface course is compared in case of considering the damage ofsubgrade or not. The damage of subgrade led to the decline in whole stiffness of thesubgrade and further lead to deterioration of the mechanical properties of the pavementstructure.