ABSTRACT
Numerical geotechnical modelling combines uncontroversial laws of equilibrium and of compatibility-continuity of displacement fields-through so-called constitutive relations which relate the changes in loads applied to elements of geotechnical materials to the deformations or gradients of displacement that develop in those elements. In this chapter we are concerned to describe some of the characteristics of the mechanical behaviour of geotechnical materials, primarily soils, which make them interesting and challenging materials to model. A hierarchy of possibilities for constitutive models that attempt to reproduce some of these characteristics is presented in Chapter 3 (see §3.4.1, for example). An extensive discussion of soil behaviour in the context of so-called 'critical state soil mechanics' is given by Muir Wood (1990) and that book will provide a complement to the descriptions of soil behaviour in this chapter.
