Numerical simulation of mixed mode (I and II) fracture behavior of pre-cracked rock using the strong discontinuity approach

The existence of macroscopic flaws in geomaterial structures profoundly influences their load-carrying capacity and failure patterns. This paper is devoted to the numerical investigation of mixed–mode fracture propagation in a cracked Brazilian disk (CBD) specimen by means of the embedded strong discontinuity approach (SDA). A recently modified nonassociated, three-invariant cap plasticity model with mixed isotropic/kinematic hardening is used to predict the continuum response for the intact part of the specimen. In addition, this constitutive model adopts bifurcation analysis to track the inception of new localization and crack path propagation. For the post-localization regime, a cohesive-law fracture model, able to address mixed-model failure condition, is implemented to characterize the constitutive softening behavior on the surface of discontinuity. To capture propagating fracture, the Assumed Enhanced Strain (AES) method is employed. Furthermore, particular mathematical treatments are incorporated into the simulation concerning numerical efficiency and robustness issues. Finally, the results obtained from the enhanced FE simulations are analyzed and critically compared with experimental results available in the literature.