ABSTRACT
Discrete element methods (Radjaï & Dubois 2011, O’Sullivan 2011) have become widespread numerical simulation tools in the investigation of the microscopic, grain-level origins of the macroscopic mechanical properties of granular materials. The essential features of the drained behaviour of sands, as classically probed in triaxial compression tests, are thus reproduced by simulations of model materials such as spherical bead assemblies (Thornton 2000, Suiker & Fleck 2004). In particular, the deviator stress maximum and the dilatant behaviour of dense samples, the monotonic deviator increase with axial strain and the contractant behaviour of loose samples, as well as the critical state approached for large strain whatever the initial density, are retrieved (Thornton 2000, Radjaï & Roux 2004). The influence of intergranular (contact) friction was assessed (Lemaître et al. 2009), and, beyond the simplest model materials, that of rolling resistance at contacts (Estrada et al. 2008), wide polydispersities (Voivret et al. 2009), non-spherical grain shapes, either smooth (Antony & Kuhn 2004) or angular (Azéma et al. 2007), have also been investigated. Most studies, however, focus on maximum deviator stress or on critical state properties, and classify initial states by their sole density (with possible, yet limited, effects of inherent anisotropy).
