DEM study of creep and stress relaxation behaviors of dense sand

Abstract

The creep and stress relaxation behaviors under the triaxial shearing of an idealized granular soil were studied using the three-dimensional discrete element method, into which the rate process theory was incorporated to enable simulation of these two time-dependent physical processes by a high-performance computing facility. The model was validated by comparing the simulation results with published experimental data. The study is focused on the effects of deviatoric stress during triaxial shearing of the granular soils on their creep and stress relaxation behaviors. In particular, to gain insights into their micromechanical mechanisms, a careful examination was made of the relationship between the shear-strain localizations occurring during creep and triaxial shearing, and the evolution of the contact number, average contact forces, and shear-induced anisotropies during these two time-dependent processes. The results indicate that the deviatoric stress level strongly affects the rates of creep strain and stress relaxation and dictates whether creep rupture will occur. These two time-dependent processes of the granular soil are also found to be isotach, which is evidenced by a unique normalized stress–strain relationship derived from the creep and stress relaxation tests.