Effect of charge coefficient on directional fracture of slotted charge

Abstract

The transmission dynamic caustics test system was carried out for blasting comparative experiments, considering varied apertures and the same charge for the same slit (symmetrical slit), investigating the effect of uncoupled charge blasting of the in-slotted charge on the propagation direction of blasting cracks. The test findings indicate that the uncoupling coefficient between the hole wall and the slit cartridge significantly affects the crack propagation direction. When the uncoupling coefficient is 1.42, the left and right main cracks form a near-horizontal angle, and reach a length of 15.5 cm. When the uncoupling coefficients are 1.71 and 1.28, the deviation angle of the main fracture is great, the propagation distance is short, and the number of secondary cracks is high, there is a trend of oscillation attenuation. Therefore, the combined action of the detonation gas and the blast stress wave has the greatest influence on fracture propagation. The appropriate uncoupling coefficient increases the quasi-static effect of the detonation gas in the direction of the slit, decreasing the impact of the detonation wave on the blast hole. The initial stress wave peak value of the wall reinforces the energy-focused directional jet effect of the slit pipe, increasing the fracture propagation distance in the slit direction. Under conditions of energy conservation, the crack propagation in the non-slit direction is inhibited.