ABSTRACT
For many years the study of the mechanical behaviour of geomaterials and their description by constitutive relationships has been developed in a framework characterized by isotropic linear elasticity (Hooke’s law) and by solid friction (Coulomb’s law). However, since the end of the 1960s the development of more powerful numerical methods such as the finite element method and the use of high-performance computers has brought to the fore of the scene the question that is becoming a crucial one: what constitutive relationships for geomaterials must be introduced into computer codes? Twenty years later, the choice is large and the state of affairs confused; we will try in this chapter to classify the various existing constitutive relations into some general classes with respect to the structure of the relationships.
