Modelling granular fragmentation in compacted systems*

The jamming of hard particles in the zero-pressure limit has been well studied, however many applications are far from this limit. As pressure increases, granular rearrangement is no longer the only mechanism for densification as grains deform and fracture. This breakdown of granular matter, or comminution, produces irregular shapes and sizes and changes macroscopic properties including rheology. We explore the compaction of brittle granular systems using large-scale discrete element simulations. Each grain is composed of many small, fundamental particles. These particles are interconnected by bonds which break under sufficient stress allowing grains to fragment into smaller grains. During loading, we monitor the evolution of stress, porosity, and distributions of grain size and shape. We characterize trends and explore the effect of strain rate and material properties. We also identify the pressure at which individual grains fracture and compare to theoretical models.