Abstract
This chapter presents general numerical methods for treating dynamical problems involving unilateral contact and dry friction. Some examples of applications related to the structural response of rigid or deformable geomaterials, such as rocks, soils, collections of blocks, granular materials, are illustrated. The chapter explains the Coulomb's dry friction law. This law is relevant for a large class of applications to geomaterials. It accounts for the main features of dry friction. It may be easily improved without drastic changes in the proposed methods. The frictional problems appear to be strongly non linear, and call for the techniques of nonsmooth mechanics. Convex analysis is widely used to formulate friction equations and numerical algorithms.