Modified Shear Spring Formulation for Discontinuous Deformation Analysis of Particulate Media

Ke and Bray (1995) presented the formulation of the discontinuous deformation analysis method (DDA) for a particulate medium consisting of two-dimensional disks. This original DDA formulation calculated the shear force at each contact by considering the incremental displacement of the shear contact spring. Other approaches that model particulate materials discretely generally use the cumulative spring displacement at each contact to calculate the shear contact force. The modifications required to implement a cumulative spring formulation in DDA are presented. A simple, single disk validation example demonstrates the improved performance of the modified algorithm. An analysis of a biaxial compression test highlights the sensitivity of the response of disk assemblies to the shear spring formulation.