10 - An Introduction to Distinct Element Modeling for Rock Engineering

Abstract

This chapter presents a general view and introduction to the distinct element method and its application in rock engineering projects. Although the distinct element method is not used as extensively as conventional continuum analysis techniques, distinct elements can fill a valuable role by providing a unique tool to evaluate the effect of rock discontinuities on engineering design. In the distinct element method, a rock mass is represented as an assemblage of discrete blocks. Joints are viewed as interfaces between distinct bodies, that is, the discontinuity is treated as a boundary condition rather than a special element in the model. The contact forces and displacements at the interfaces of a stressed assembly of blocks are found through a series of calculations, which trace the movements of blocks. Movements result from the propagation through the block system of a disturbance applied at the boundary. This is a dynamic process, in which the speed of propagation is a function of the physical properties of the discrete system. The dynamic behavior is described numerically by using a timestepping algorithm, in which the size of the timestep is selected. The distinct element method is based on the concept that the timestep is sufficiently small that, during a single step, disturbances cannot propagate between one discrete element and its immediate neighbors.