Fracture propagation and coalescence at bedding plane in layered rocks

Fracture propagation, fracture coalescence, and their interactions with the bedding plane in layered rocks are of great significance when conducting a stability analysis of structures on or within the layered rock mass. In this work, we developed a numerical model by the inserted cohesive element (CE) method to simulate the evolution of fracture paths in layered rocks, then validated it with modified wedge splitting tests. The results indicate that the fracture penetration/deflection behaviour at the bedding plane is controlled by two strength thresholds of the bedding plane: 1) If the bedding plane strength > threshold I — the fracture directly penetrates the bedding plane; and 2) If threshold I > bedding plane strength > threshold II — first, the fracture deflects along the bedding plane without any daughter fractures or penetration, and then one or two daughter fractures can form. A two-flawed model is used to simulate the fracture coalescence. The fracture coalescence is first determined by the bedding plane's strength thresholds. If bedding plane strength > threshold I, fracture coalescence can occur only if the second flaw is located within a certain range. No coalescence occurs if the bedding plane strength