STUDY ON DYNAMIC PROPAGATION CHARACTERISTICS OF BLASTING CRACKS IN DIFFERENT COUPLING MEDIA

The uncoupled charging structure can effectively improve the blasting effect. In order to explore the impact of different coupling media on the blasting effect, the transmission digital laser caustics experimental system is used to carry out the uncoupled blasting test of polymethyl methacrylate (PMMA) specimens in three coupling media, i.e., water, air and sand, to study the crack morphology after blasting in different coupling media, calculate the fractal dimension of the crack, and quantitatively evaluate the degree of rock damage. The dynamic mechanical behavior of crack initiation under different coupling media is compared by analyzing the change law of crack growth speed and dynamic stress intensity factor. Through combining numerical simulation for auxiliary analysis, it explains the influence of different coupling media on the range of blasting damage, the time curve of hole wall pressure, and the total energy curve of the rock model in numerical simulation. Results show that after water coupling explosion, the crack analysis dimension is the largest, and there are many cracks around the blast hole. Mhe main crack propagation length is the largest, and the blasting effect is the best. Sand soil coupling blasting requires more energy to make the crack tip crack, and its dynamic stress intensity factor is the largest. The simulated damage contour is consistent with the experimental results. The water coupling damage range is the largest, followed by air coupling. The sand soil coupling damage range is concentrated around the borehole. The time history curves of hole wall pressure and energy validate the results of blasting experiments, indicating that water coupled blasting can better utilize blasting energy and improve the failure effect of the specimen.