Why modeling particle shape matters: significance of particle-scale modeling in describing global and local granular responses

The applicability of particle-scale modeling using the discrete element method (DEM) is typically evaluated by comparing simulation results with stress-strain responses observed in elementary tests. This validation at the global level may not guarantee that the simulation can capture realistic particle-level motion. Thus, this study investigated the applicability and limitation of two types of DEM models, through the comparison with experimental results of biaxial shearing tests on bidisperse granular assemblies comprising circular (round) and hexagonal (angular) particles under various confining pressures. Experimental data wherein particle rotations were identified by novel image analysis technique is used to evaluate whether the DEM models could accurately reproduce macroscopic stress-strain relationships and microscopic particle responses. Experimental findings suggested that particle rotations play a crucial role in granular deformation and are influenced by the particle shape. A detailed DEM model with precise particle shapes effectively replicates both macroscopic stress-strain relationships and microscopic responses, including particle rotation and interlocking at global and local levels. Conversely, a simpler ad hoc DEM model, which incorporates rolling resistance for circular particles, can imitate the stress-strain relationships of hexagonal particles but falls short in replicating microscopic responses accurately