Modelling of Anisotropic Elastoplastic Damage in Claystones

ABSTRACT: This paper is devoted to the constitutive modelling of coupled elastoplastic damage in a hard claystone. A summary of experimental data, obtained from triaxial compression tests including unloading cycles, is first presented. These results show an important plastic deformation which is coupled with an induced anisotropic damage. The latter is due to initiation and growth of oriented microcracks that lead to directional deterioration of elastic properties. A constitutive model coupling plastic deformation and induced anisotropic damage is then proposed. The plastic behaviour is described by a typical cohesive-frictional model. Damage is represented by a second rank symmetric tensor. The damage evolution rate is related to tensile strains. The damage effect on plastic flow is also considered. A simple procedure for the determination of model parameters from standards tests is proposed. The validity of the model is checked against experimental data in various loading conditions and water contents.