Rolling resistance as a surrogate for angularity in DEM: Macromechanical potentials and micromechanical limitations

In this study, a calibrated DEM model of biaxial shearing tests was used to simulate polygon-shaped particles with varying corner numbers, representing different degrees of roundness (R). Simultaneously, rolling resistance (μ r ) was applied to conventional circular particles as a surrogate for shape angularity. The μ r values were systematically calibrated to reproduce the stress–strain behaviour of the polygonal particles. Comparative analyses were then conducted at both macro- and micro-scales to evaluate the validity of the μ r -based approximation. At the macroscopic level, the rolling resistance approach successfully captures the critical state stress ratio for all polygonal particles. At the microscopic scale, the μ r approach reasonably reproduced key features such as particle rotations, coordination numbers, and contact force distribution for particles with moderate roundness (R > 0.5). However, for more angular particles (R ≤ 0.5), the μ r approach failed to replicate the micromechanical behaviours inherent to angular shapes, despite aligning well in macroscopic stress–strain response. This limitation is primarily attributed to the absence of microstructural mechanisms unique to angular geometries, such as interlocking and the eccentric contact force paths, that inherently both induce and resist particle rotation. In contrast, rolling resistance solely resists rotation. This study highlights the importance of recognizing the limitations of rolling resistance in representing the micromechanics of angular particles. Careful interpretation is necessary to avoid misrepresenting underlying behaviours when modelling particle shape effects using this simplified approach.