Study on fracture behavior of bedded shale in three-point-bending test based on hybrid phase-field modelling

摘要

In this paper, a hybrid phase field modelling is implemented to investigate the fracture behavior of bedded shale. The model first is compared with the anisotropic phase field model and is validated by a benchmark test. Subsequently, three-point-bending tests are conducted on bedded shale and the corresponding simulations are done by hybrid phase field model. The numerical results are in good agreement with experimental results. Furthermore, the sensitivities of bedding parameters are studied by designed simulation cases. The smaller bedding parameters correspond to the more obvious anisotropy of shale and the more complex crack propagation path. Both Young's modulus ratio and critical energy release rate ratio have vital impacts on the fracture toughness and failure pattern of bedded shale, whereas, their contributions are slightly different. The increase of them results in fracture propagation along the bedding plane when bedding angles are 30 degrees and 60 degrees. The crack propagation across the bedding plane also occurs, which depends on the ratio of parameters between bedding plane and matrix. Overall, the Young's modulus has a greater impact on the peak load and fracture toughness, but the critical energy release rate plays a more significant role in the failure pattern of bedded shale.