The use of numerical modelling has begun a revolution in the available tools and methods with which to study geomechanics. This involves the analysis of geomaterials : materials whose mechanical behaviour depends on the pressure to which they are subjected. These are mainly concrete, soils and rocks. This publication extensively covers numerical modelling which makes possible the application of numerical methods to a range of materials and topics. These include brittle and ductile materials, water saturated and partially saturated geomaterials, large and samll strains, steady state and transient problems, soil dynamics, strain localization, and applications related to natural hazards. The various contributors to this volume cover not only the theoretical aspects of the subject, the main emphasis of the contents, but also practical examples of the effects of such factors as chemical degradation, rock weathering, and debris flows and flow slides.