Elastic–Plastic Fracture Propagation Modeling in Rock Fracturing via Punch Through Shear Test

Abstract

Fracture initiation and propagation from a wellbore within a rock formation exhibit nonlinear and inelastic behaviors. When the rock material undergoes plastic deformation prior to failure, the classical Griffith theory is no longer valid. In this study, a variational phase-field approach is applied to model the inelastic behavior of granite rock in a punch through shear test. The rock failure and the fracture initiation and propagation during the loading was simulated and compared to the corresponding experimental investigations. In this numerical approach, the total local free energy is fully coupled with solid deformation and computes the plastic strain rate. The code is scripted in Multiphysics Object Oriented Simulation Environment (MOOSE). The model is shown capable of reproducing the evidenced phenomena from Punch Through Shear (PTS) test encompassing mixed mode fracture pattern Mode I, and Mode II. The numerical results show a good agreement in the stress–displacement curve with experimental data for the critical energy release rate of $${G}_{c}=600\mathrm{N}/\mathrm{m}$$ . Therefore, the granite sample’s fracture toughness for Mode II is calculated to be 4.85 $$\mathrm{MPa}\sqrt{\mathrm{m}}$$ at no confining pressure.