Modeling Soft Granular Materials Under Compaction: Strain Rate Effect

Abstract Soft granular materials are assemblies of particles that undergo large deformations without breakage under load. Clay aggregates and wet agglomerates are examples of soft particles. In this paper, we study the compaction of such materials for a better understanding of the effect of softness and we focus more specifically on the strain rate effect. We use a numerical approach that is based on a combination of an explicit total Lagrangian formulation of the Material Point Method with the Contact Dynamics method. For different values of the strain rate, we study the compaction of an assembly of soft grains up to very high levels of packing fraction in terms of the global stress, grain shape and coordination number. We show three regimes of compaction: rearrangements without significant shape change, rearrangements induced by shape change, and shape change without significant rearrangements. The transition points depend on the strain rate.