Analysis of explosion wave interactions and rock breaking effects during dual initiation

In blasting engineering, the location and number of detonation points, to a certain degree, regulate the propagation direction of the explosion stress wave and blasting effect. Herein, we examine the explosion wave field and rock breaking effect in terms of shock wave collision, stress change of the blast hole wall in the collision zone, and crack propagation in the collision zone. The produced shock wave on the collision surface has an intensity surpassing the sum of the intensities of the two colliding explosion shock waves. At the collision location, the kinetic energy is transformed into potential energy with a reduction in particle velocity at the wave front and the wave front pressure increases. The expansion form of the superposed shock wave is dumbbell-shaped, the shock wave velocity in the collision area is greater than the radial shock wave velocity, and the average propagation angle of the explosion shock waves is approximately 60°. Accordingly, a fitted relationship between blast hole wall stress and explosion wave propagation angle in the superposition area is plotted. Under the experimental conditions, the superimposed explosion wave stress of the blast hole wall is approximately 1.73 times the single-explosion wave incident stress. The results of the model test and numerical simulations reveal that large-scale radial fracture cracks were generated on the blast hole wall in the superimposed area, and the width of the crack increased. The width of the large-scale radial fracture cracks formed by a strong impact is approximately 5% of the blast hole length. According to the characteristics of blast hole wall compression, the mean peak pressures of the strongly superimposed area are approximately 1.48 and 1.84 times those of the weakly superimposed and nonsuperimposed areas, respectively.