Formulation and application of a short-term strength criterion for isotropic rocks

Abstract

This paper deals with failure of low-porosity rocks and with a multiaxial representation of the corresponding surface in stress space. The proposed failure criterion is based on a mathematical modification of the MSDP function recently developed by the same group. This three-dimensional criterion has been reformulated so that it can be expressed in a unified manner, without having to resort to a transition condition between the curved portion (referred to as the Mises-Schleicher portion) and the linear portion (referred to as the Drucker-Prager portion). The new failure surface has the following characteristics: a forced passage through the uniaxial strength in tension (σt) and in compression (σc), a continuous influence of the minor principal stress for the entire range of behavior considered, a strength under high confining stress that is controlled by the basic friction angle ϕband a loading-geometry effect expressed in the π plane. This new expression of the criterion is presented in the paper. Its main characteristics are also shown, together with its application to various low-porosity rocks using a number of testing results taken from the literature. In the discussion that follows, other attributes of the criterion are highlighted using a qualitative comparison with the Hoek-Brown criterion. Key words: rock mechanics, failure surface, failure criterion, laboratory testing.