Constitutive models for compressive loading of geologic materials

This paper addresses some aspects of the theory of plastic straining which unify the constitutive equations for geologic materials under compressive loading. Existing models are generalized with particular emphasis on ascertaining the minimum number of phenomenological coefficients required to adequately represent these models. Results show that both single- and multiple-mode plasticity models may be generalized to the same form. Five phenomenological coefficients are adequate to describe the response of strain-hardening materials to compressive loading.