Phase-field modeling for dynamic cracking behavior in bedded shale

Abstract

The bedding plane with the special structural characteristics may have a significant influence on the cracking behavior induced by stress wave in bedded shale. This study proposes a novel phase-field model to predict the dynamic crack propagation path in bedded shale. The bedding plane is assumed to be the thin elastic layer with the certain thickness and independent mechanical parameters. Because its thickness is tiny compared with rock matrix, the lower-dimensional interfacial element is employed to discretize it together with rock matrix within finite element framework. The fractures within bedding plane and rock matrix share a phase-field variable. However, the governing equations of the phase-field evolutions in bedding plane and rock matrix have different driving forces, and such operation greatly increases the robustness of the model. Based on this model, the dynamic cracking behavior of bedded shale is investigated numerically. The results indicate that the mechanical properties of bedding planes are the key factors affecting the overall cracking behavior of bedded shale. Our research provides a valuable insight in cracking behavior of bedded shale in dynamic fracturing for shale gas development.