Significant progresses have been made on the study of mechanical properties and fracture propagation of shale based on Brazilian tests and uniaxial/triaxial compression tests. The study found that the fracturing behavior of shale is controlled by the complicated interactions of bedding planes (joints) and rock matrix. However, how joint properties affect shale fracturing behavior is still unclear. This paper establishes a bonded-particle model with embedded smooth joints to simulate the fracturing behavior of shale under notched three-point-bending tests. Firstly, a bonded-particle model is established for the notched beam specimens embedded with bedding planes. Secondly, this model is validated by our experimental results under notched three-point-bending tests. The load-displacement curves, the peak load and the failure pattern are compared between numerical simulations and experimental results. Finally, the effects of smooth joint strength and shear-to-tensile strength ratio on tensile strength, fracture toughness and failure pattern are comparatively studied at different inclined angles. Numerical results show that joint parameters contribute greatly to tensile strength, fracture toughness and failure pattern. Joint strength mainly contributes to tensile strength and fracture toughness while shear-to-tensile strength ratio plays a more important role in failure pattern.
Keywords: Shale, Joint parameters, Fracturing behavior, Notched three-point-bending test, Discrete element model