Numerical Investigation of Deformation Response and Stress-Path Evolution in a Multilayer Road System Under Repeated Moving Vehicle Loads

Under the cyclic traffic loading, roads often experience deformation accumulation, which impairs their service performance and shortens their service life. Therefore, investigating such issues is of great importance to road engineering. This study develops a multi-layer finite element model for an unsaturated road system consisting of the pavement, unsaturated base, subbase, and subgrade. The Mohr-Coulomb (M-C) model is used for the pavement, base, and subbase, while the bounding surface model (BSM) is implemented via ABAQUS subroutines for the subgrade. Moving vibratory traffic loads and pavement friction are applied via the DLOAD and UTRACLOAD subroutines. Parametric analyses are conducted to evaluate the effects of base saturation, load amplitude, and friction coefficient on road deformation. The results indicate that under cyclic loading, the subgrade deforms both vertically and laterally. The deformation increases significantly with increasing base saturation and load amplitude. The friction coefficient affects the stress-path distribution of the road system. These findings provide necessary theoretical basis for optimizing road structure design and improving service performance.