Investigation on the rate-dependent behavior of sands via DEM

Abstract

A series of drained triaxial compression tests were performed with different loading rates via the Discrete Element Method (DEM) to analyze the rate-dependent behavior of cohesionless sand. In the DEMDiscrete Element Method (DEM) model, the rolling resistance contact was employed to replicate the non-spherical particle shape and interlocking effects of solid grains. To investigate the strain rate sensitivity of sands, four loading rates were adopted, namely, 1.25, 0.125, 0.0125, and 0.0025 %/min, respectively. Meanwhile, parametric studies on five microscopic parameters, namely the internal friction angle (θ), normal stiffness (kn), tangential stiffness (ks), coefficient of rolling stiffness (β), and coefficient of plastic moment (η) have been carried out to consider their influence on the macroscopic rate-dependent behavior of sands. The results of DEMDiscrete Element Method (DEM) simulations reveal that the strain-rate sensitivity of sand samples decreases with the increased internal friction angle of particles, while both normal stiffness and tangential stiffness have minor effects on the rate-dependent behavior for loose samples. However, for dense samples, with the increasing of stiffness, the rate-dependent behavior of sand becomes gradually obvious. It is also demonstrated that the coefficient of rolling stiffness and plastic moment are in non-linear correlation with rate-dependent behavior of sands.