Cracking behavior and damage mechanism for jointed rock mass under the coupling effect of confining pressure and blast

Propagation features of explosion-induced stress waves undergo substantial alterations as they traverse heterogeneous interfaces. In rock engineering, the prevalence of discontinuous structural planes, such as joints and fissures, becomes increasingly pronounced with increasing burial depth. To gain a comprehensive insight into the dynamic response and damage mechanism, this paper adopted an explicit dynamics numerical method that integrates the ALE algorithm and fluid-solid coupling technology, which enables precise simulation of the fracture process within jointed rock mass under the combined effects of confining pressure and blast. Based on the time-domain recurrence theory, the transmission and reflection coefficients of stress wave were calculated respectively, and then propagation process and features of stress wave were analyzed by the explosion photoelasticity test. Additionally, Riedel-Hiermaier-Thoma (RHT) damage model was employed to investigate the influence of varying joint angles and confining pressures on cracking behavior. Furthermore, the cracks were quantitatively assessed using the FracPaQ program. Finally, the damage mechanism of the jointed rock mass was revealed by analyzing the principal stress distribution and displacement change of the joint tip. The results showed that both the joint and the maximum pressure have a guiding effect on crack extension, and this effect will be weakened by the presence of the joint. When the maximum pressure is perpendicular to the joint surface, the coefficients of transmission and reflection tend to increase and decrease with the pressure increasing, respectively. From the change rule of normal and tangential displacement on both sides of the joint surface, it is found that shear stress is the main cause of tip-wing crack expansion. And judging from the dynamic stress intensity factors (DSIFs), tensile cracks dominate the damage of the tip at the early stage of the blasting, while shear cracks dominate at the later stage.