Modeling of elastoplastic damage behavior of a claystone

This paper is devoted to the constitutive modeling 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 damage is due to initiation and growth of oriented microcracks and manifested as directional deterioration of elastic properties. Influences of mineral compositions and water content on the mechanical behaviour are also investigated. A constitutive model is then proposed for the description of plastic deformation and induced damage. The plastic behaviour is described by a typical cohesive-frictional model. The material damage is represented by a second rank symmetric tensor. The damage evolution rate is related to both elastic and plastic 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 tested for different loading paths by comparing numerical simulations and experimental data.