Micromechanical investigation of the effect of an imposed stress state change during drained cyclic loading using DEM

Abstract

This study investigates the effect of a stress state change at an intermediate stage during cyclic loading on the drained cyclic deformation of soil using Discrete Element Method (DEM) simulations. Drained cyclic triaxial simulations were conducted on an assembly of irregularly shaped particles, with the stress state shifting along different stress paths at an intermediate stage of cyclic loading. The analysis of the macro- and microscopic responses reveals a link between the cyclic stress–dilatancy behaviour and the anisotropy of the granular assembly. In the simulations without the stress state change or with a stress ratio increase, the strain accumulation direction aligns with the prediction of the Modified Cam Clay (MCC) flow rule; and the strain accumulation is faster at higher stress ratios when the contact distribution is more anisotropic. However, when the particle assembly experiences a stress ratio decrease during cyclic loading, the subsequent strain accumulation direction deviates from the MCC flow rule, and strains accumulate more rapidly at lower stress ratios when the contact distribution is nearly isotropic. A tentative explanation is proposed to explain the altered strain accumulation direction after the stress ratio decrease.