Capturing nonspherical shape of granular media with disk clusters

In discrete numerical modeling of granular materials, idealization of individual particles is required, as it is not practical to model a large number of particles, each with its actual shape and size. To minimize computation times, researchers often use two-dimensional, circular elements. However, biaxial and direct shear tests on such specimens result in low strengths compared to granular materials, due, in part, to excessive rolling of the perfectly circular particles. In this paper, a new particle type, disk clusters, is presented. A disk cluster is a group of circular disks permanently connected to form an irregularly shaped particle that more closely represents the shape of granular materials and has less tendency to rotate. Development and implementation of disk cluster particles into a discontinuous deformation analysis program is presented. Validations of the mechanics of a single disk cluster, biaxial shear, and anchor pullout simulations illustrate the usefulness of this new particle type.