Influence of quasi-static loading rates on crushable granular materials: A DEM analysis

Abstract

Does granular material show strain rate dependent response, especially with quasi-static loading condition? The answer is both yes and no since it depends on various factors like particle shape, size and crushability. In the present study, a micromechanical analysis is carried out using discrete element modelling (DEM) to explore the effects of variation in the loading rates, within/near the quasi-static regime, on the stress-strain response of crushable and non-crushable granular assemblies. The study considers monotonic loading at two different strain rates and a sudden strain rate shift condition. The numerical simulation of one-dimensional (1D) compression shows quasi-static loading, which usually produces rate-independent response, can demonstrate rate-dependent features during particle crushing. The variation in the contact force distribution within the granular assembly at different loading rates, dictates the stress response and the crushing events. Relatively low strain rate compression favors homogeneous crushing involving a large number of particles that consequently reduces the strength via fragments rearrangement. Conversely, high strain rate promotes localized crushing within fewer particles, and thus strain hardening is observed. Sudden strain rate shift within the granular assembly creates a discontinuous velocity profile that hampers the crushing events.