Experimental study on the interaction mechanism of two dynamic cracks under blasting loading

In this study, dynamic photomechanical blasting experiments were conducted to investigate the interaction mechanisms of dual cracks induced by explosions at different relative positions. The experimental results demonstrate that both cracks penetrate when the actual relative vertical distance at which the crack tips begin to interact is within 10 mm in the experimental group; however, when it exceeds 10 mm, the dual cracks finally expand in a relatively parallel manner. The relative horizontal distance has a weaker impact on the final fracture mode. When the dynamic cracks begin to interact, both the propagation speed of the crack tips and the stress intensity factor increase, the crack propagation angle increases, and the crack propagation path exhibits curved characteristics. Based on the final fracture states of the specimens, the interaction results of the crack tips can be classified into three categories: deflection without merging, curvilinear merging, and parallel overlapping without merging. Based on the results of dynamic photomechanical experiments and the relative verification theory of the crack-tip stress field in previous studies, an expression for the stress-field distribution between dynamic crack tips during interaction was proposed. During the interaction of dynamic blast-induced cracks, the stress intensity at crack tips increases to 1.3–1.5 times that at the onset of mutual interaction. The cracks initially repel each other. As the relative positions of the crack tips increased, the local stress weakened, and the repulsion phenomenon diminished accordingly. Consequently, after crack interaction, the cracks exhibited a spindle-shaped pattern.