The deformation of granular materials under repeated traffic load by discrete element modelling
The deformation of the gravel soil is an important component of the total settlement of the pavement under traffic load. The traffic load induces a heart-shaped stress path in the deviatoric stress space characterised by the rotation of principal stress. However, cyclic triaxial tests are usually carried out to investigate the deformation of gravel soil, which cannot account for the effect of principal stress rotation. In this study, discrete element method (DEM) is used to investigate the response of granular soil subjected to a heart-shaped stress path, and the results are compared with cyclic simple shear tests and biaxial tests. The results indicate that the accumulated volumetric strain of the soil increases with increasing cyclic stress ratio and initial confining pressure. Meanwhile, the accumulated volumetric strain changes from contractive to dilative when the cyclic stress ratio increases from 0.3 to 0.7. At the particulate level, the degree of fabric anisotropy increases and the principal direction of the fabric rotates accordingly in the cyclic loading. The results also show that the accumulated volumetric strain under heart-shaped stress path is much larger than that in cyclic biaxial tests, indicating the significance of principal stress rotation in soil deformation.
Keywords: Granular soil, accumulated deformation, traffic load, principal stress rotation, discrete element method, micromechanics