Discrete-Element Analysis of Fracture Characteristics for Transversely Isotropic Sandstone with U-Notches

Abstract

Engineering rock mass often involves bedding planes and U-shaped defects. Under the combined influence of bedding planes and defects, the fracture mode of engineering rock mass is more complicated. To better understand the failure law of U-shaped defects in rock mass with bedding planes and better control or predict the crack propagation morphology, three-point bending tests were conducted on semicircular disk specimens with U-shaped notches under three different notch radii. The load variation law, different stages of the load–displacement curve, and fracture characteristics of specimens under five bedding angles were analyzed. Then, numerical models of semicircular three-point bending tests were established in particle flow code 2D (PFC2D). The influence of notch radius and bedding angle on the failure path of semicircular specimens was simulated and analyzed, and the three failure modes were verified again. In addition, the stress at the notch tip of the model was monitored by the measurement circle in the discrete-element method, and the fracture toughness of the model specimen was calculated, which provides a new calculation idea for fracture toughness. The research results help us more comprehensively understand the mechanical behavior and failure characteristics of layered rock mass with notch under external load.