Investigation on cracking behavior and influencing factors of jointed rock masses under the coupling effect of confining pressure and blasting

Propagation features of blast-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, an explicit dynamics numerical method incorporating the ALE algorithm and fluid-solid coupling technology was adopted, which allows for precise simulation of the fracture process within jointed rock mass under the combined effects of confining pressure and blasting load. Based on the time-domain recurrence theory, the transmission and reflection coefficients of the stress wave were calculated, and the propagation process and features of the stress wave were then analyzed by the explosion photoelasticity test using an epoxy resin plate. Additionally, the Riedel-Hiermaier-Thoma (RHT) damage model was used to investigate the influence of different 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 as well as the dynamic stress intensity factors (DSIFs) of the joint tip. The results show that both the joint and the anisotropic pressure have a guiding effect on crack extension, and the effect of the anisotropic pressure will be weakened by the presence of the joint. For the anisotropic pressure condition, the stress wave transmission and reflection coefficients tended to decrease and increase, respectively, with increasing pressure in the horizontal direction. 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. An analysis of the DSIFs reveals that tensile cracks predominantly contribute to damage at the joint tip during the initial phase of blasting, with shear cracks becoming the dominant form of damage in the later stages.