Incremental response of granular materials: DEM results

TL;DR

This study uses DEM simulations to analyze how dense 2D granular materials respond incrementally under biaxial compression, revealing elastoplastic behavior with coupled shear responses and contact friction effects.

Contribution

It provides a detailed DEM-based analysis of incremental elastic and irreversible strains in granular materials, highlighting the coupling effects and friction mobilization.

Findings

Response follows elastoplasticity with Mohr-Coulomb criterion

Nonelastic shear strains occur for shear stress increments

Shear and in-plane responses are coupled due to contact friction

Abstract

We systematically investigate the incremental response of various equilibrium states of dense 2D model granular materials, along the biaxial compression path (\sigma 11 < \sigma 22, \sigma 12 = 0). Stress increments are applied in arbitrary directions in 3- dimensional stress space (\sigma 11, \sigma 22, \sigma 12). In states with stable contact networks we compute the stiffness matrix and the elastic moduli, and separate elastic and irreversible strains in the range in which the latter are homogeneous functions of degree one of stress increments. Without principal stress axis rotation, the response abides by elastoplasticity with a Mohr-Coulomb criterion and a non-associated flow rule. However a nonelastic shear strain is also observed for increments of \sigma 12, and shear and in-plane responses couple. This behavior correlates to the distribution of friction mobilization and sliding at contacts.