Effect of Particle Shape on Constitutive Relation: DEM Study

The influence of particle shape was evaluated under drained and undrained (constant volume) condition using three-dimensional (3D) cubical assemblies of spheres, ellipsoids, and cluster of spheres (a combination of seven spheres with two different degrees of overlap) with same particle size distribution. It was found that the peak deviatoric stress, the minimum dilatancy (d=dϵvp/dϵqp), corresponding stress ratio (dmin), the bounding surface dilatancy model, and the location of the critical state line (CSL) both in the e-log(p′) and the q-p′ space were influenced by particle shape. Therefore, four corresponding sets of constitutive parameters for four different particle shapes were implemented in a bounding surface model to predict both drained and undrained (constant volume) discrete element method (DEM) simulation. Good prediction, irrespective of particle shape, indicates that the observed DEM behavior can be adequately captured by the theories of continuum mechanics. Importantly, the majority of the constitutive parameters were influenced by particle shape and can be correlated with simple shape descriptor of sphericity.