Induced anisotropic damage and plasticity in initially anisotropic sedimentary rocks

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This work is devoted to the description of plastic deformation and induced damage in sedimentary rocks with structural anisotropy. Due to oriented growth of microcracks, the damage leads to an induced anisotropy in materials. The emphasis is put on the coupling between the inherent and induced anisotropies. A fabric tensor is first defined in order to characterize the inherent orientation-dependent properties of materials. A discrete thermodynamic approach is then extended. Macroscopic plastic deformation and material damage are considered as the result of frictional sliding along weakness planes randomly distributed in spatial orientations. Local plastic flow rule and damage evolution law are formulated for each family of weakness planes. The mechanical properties in each orientation depend on the inherent anisotropic structure. The coupling between the inherent and induced anisotropies is properly described using the fabric tensor and discrete approach. A series of numerical simulations are performed in order to verify the predictive performance of the proposed model. Comparisons between numerical results and test data show the present model is able to describe the main mechanical behaviors of anisotropic geomaterials, by taking into account the coupling between the inherent and induced anisotropies.