Unified soil behavior of interface shear test and direct shear test under the influence of lower moving boundaries

Based on a detailed analysis of DEM simulation data,this paper provides new insights into the effects of boundary surface topography on the mobilized stress ratio and stress-displacement behavior in the interface shear test and the direct shear test. The soil mechanics observed in the two types of tests are unified under a novel perspective of boundary-induced soil behavior. It is shown that the principal direction of the contact force anisotropy developed at the soil-surface boundary has an exclusive control over the peak stress ratio measured both at the boundary and inside the sampling window. However, a subtle change in the roles of the principal direction and the magnitude of contact force anisotropy is found as the contact force chains extend from the surface into the interphase soil.