Time-Dependent Propagation of 3-D Cracks in Rocks Under Hydromechanical Coupling

Crack propagation and rock failure under hydromechanical coupling have typical time-dependent characteristics, and the subcritical crack propagation is one of the most important causes of rock instability. Rheological tests based on mortar specimens containing single internal 3-D cracks and the corresponding numerical simulations are carried out to investigate the time-dependent characteristics of the crack propagation, the failure mode of rocks, and the effects of water pressure and crack dip angle. The mortar specimen exhibits a tensile-shear failure mode under the hydromechanical coupling as observed in rheological tests, and a macro-fracture penetrates the upper and lower ends of the specimen. The propagation rate of the crack decreases first and then increases. The crack propagation can be divided into three stages according to the relationship between the propagation rate and fracture parameters. The water pressure significantly reduces the time required for rock failure due to its promoting effect on the crack propagation rate, which has negative effects on the long-term stability of rocks. Cracks with a dip angle of 45° are more likely to cause rock failure under hydromechanical coupling, while cracks with larger dip angles exhibit a better long-term stability.