Evolution of blasting cracks in different static compression fields

The blasting-induced fracture of deep underground rock is the main problem in rock blasting, which is commonly subjected to the dynamic loads induced by blasting under high in-situ static stresses. The high static stress fields have great influences on the fracturing behaviors of propagating cracks. The digital-laser dynamic caustics system is utilized in the blasting fracturing tests, in which the PMMA specimen undergoes three kinds of vertical static stresses (0, 2 and 4 MPa, respectively) with the same total charges. Using the theory of fracture mechanics, the mechanism of fracture and propagation behaviors of cracks is analyzed. The results indicate that the propagation direction of the main crack gradually deflects to the direction of the principal stress, the total propagation time of the main crack decreases gradually, the type II test failure is more remarkable, and the maximum deflection angle of the main crack also significantly increases along with the increase of the initial static compression. The relationship between the static compression stress field and the blast-induced cracks behavior is revealed, and the studies on rock blasting fragmentation theory are enriched.