A microcrack-based continuum damage model for initially anisotropic sedimentary rocks

In present work, a new microcrack-based anisotropic damage model is proposed for initially anisotropic rocks, such as sedimentary rock. A second-order damage tensor is adopted to represent the density and direction of the microcracks. The anisotropic mechanical damage evolution law is determined by the propagation of microcracks. Local tensile stress and linear elastic fracture mechanics are used to describe the propagation of microcrack. The orientation of bedding plane is also taken into account in damage evolution equation. The constitutive equations are developed by considering the coupling effects between the inherent and induced anisotropies. The model parameters can be determined by triaxial compression tests of rocks with different bedding orientations. The proposed model is applied to describe the mechanical behavior of a typical sedimentary rock. The experimental and simulated results are in good agreement. The model can capture the general anisotropic behavior and damage properties of the initially anisotropic rocks. Due to the crack-controlled model, snap-back behavior in the early softening regime is also captured.