Analysis of explosion wave interactions and rock breaking effect in dual initiation

In blasting engineering, the location and number of detonation points, to a certain extent, determine the propagation direction of the explosion stress wave and blasting effect. In this study, the explosion wave field and rock-breaking effect are investigated on three aspects: shock wave collision, stress change of the blast hole wall in the collision zone, and crack propagation in the collision zone. The intensity of the resulting shock wave on the collision surface exceeded the sum of the intensities of the two colliding explosion shock waves. At the collision location, the kinetic energy was converted into potential energy with a decrease in the particle velocity at the wave front, and the wave front pressure increased. The expansion form of the superposed shock wave was dumbbell-shaped, the shock wave velocity in the collision area was higher than the radial shock wave velocity, and the average propagation angle of the explosion shock waves was approximately 60°. Accordingly, the relation between the blast hole wall stress and the explosion wave propagation angle in the superposition area was fitted. Under the experimental conditions, the superimposed explosion wave stress of the blast hole wall was approximately 1.73 times the single-explosion wave incident stress. The model test and numerical simulation results showed that large-scale radial fracture cracks were formed on the blast hole wall in the superimposed area, and the crack width increased. The width of the large-scale radial fracture cracks formed by a strong impact was approximately 5% the blast hole length. Based on the characteristics of blast hole wall compression, the mean peak pressure of the strongly superimposed area was approximately 1.48 and 1.84 times those of the weakly superimposed and nonsuperimposed areas, respectively.