Computational procedure for long-term settlement of layered medium under cyclic dynamic loads

The formulations of some variables were presented for two essential problems of long-term settlement of traffic infrastructures, which were dynamic stresses under the moving strip load, residual stresses, permanent strain and residual settlement induced by traffic loads. The analytical solutions of the dynamic stresses were given for the plane problem of layered medium under the moving strip load by using Fourier integral transform and transfer matrix method, and these solutions were derived from the dynamic differential equation, boundary conditions and continuous conditions between each two layers. A new empirical formulation of permanent strain was proposed by incorporating the influences of stress level and stress path. Then the expressions were offered for the residual stress and long-term settlement of layered medium under cyclic dynamic loads, which was derived from solving an elastic boundary value problem without any dynamic load but with the permanent strain. The variations of long-term settlement on the surface of layered medium were investigated for some cases of circular track tests for semi-rigid base asphalt pavement. The reasonability and the reliability of the method were verified by the comparison between the test results and the predicted results under three types of subgrade soils.