ABSTRACT

This chapter introduces the constitutive models for agricultural soils in three categories: elastic, plastic and dynamic models. It begins with some basic concepts of stress and strain. The incremental stress-strain relations for an elasto-plastic material are established on the basis of three basic assumptions: yield and failure criteria, flow rule and hardening law. Constitutive models refer to the description of the relation between stress and strain with time being considered for dynamic cases. Constitutive models can be classified into several categories on the basis of different criteria: Linear and non-linear models — which depend on the linearity of equation; Elastic, plastic and elasto-plastic models — which depend on whether only elasticity or plasticity or the both are considered in modeling or not. Constitutive models associated to plasticity can generally be divided into two types: Rigid, perfectly plastic models and Elasto-plastic models.