Capability of discrete element method to investigate the macro-micro mechanical behaviours of granular soils considering different stress conditions and morphological gene mutation

Abstract

Discrete element method (DEM) has been widely utilised to model the mechanical behaviours of granular materials. However, with simplified particle morphology or rheology-based rolling resistance models, DEM failed to describe some responses, such as the particle kinematics at the grain-scale and the principal stress ratio against axial strain at the macro-scale. This paper adopts a computed tomography (CT)-based DEM technique, including particle morphology data acquisition from micro-CT (μCT), spherical harmonic-based principal component analysis (SH-PCA)-based particle morphology reconstruction and DEM simulations, to investigate the capability of DEM with realistic particle morphology for modelling granular soils' micro-macro mechanical responses with a consideration of the initial packing state, the morphological gene mutation degree, and the confining stress condition. It is found that DEM with realistic particle morphology can reasonably reproduce granular materials’ micro-macro mechanical behaviours, including the deviatoric stress–volumetric strain–axial strain response, critical state behaviour, particle kinematics, and shear band evolution. Meanwhile, the role of multiscale particle morphology in granular soils depends on the initial packing state and the confining stress condition. For the same granular soils, rougher particle surfaces with a denser initial packing state and a higher confining stress condition result in a higher degree of shear strain localisation.