Model experimental study on controlled blasting of slit charge in deep rock mass

The ground stress in deep rock masses has a significant effect on directional fracturing during slit charge blasting. In this paper, an experimental system of digital laser dynamic caustics and a static-dynamic combination loading system were used to study crack propagation behavior related to slit charge blasting with different initial compressive stress (simulating the ground stress) and different angles between the slit direction and initial compressive stress. The experimental results show that when the slit direction is perpendicular to initial compressive stress direction, crack propagation is suppressed and the greater initial compressive stress, the more obvious the effect. When the angle between the slit direction and initial compressive stress is 45°, initial compressive stress changes the crack propagation mode, which indicates a transition from mode-I to the mixed-mode I–II fracture. With the increase of compressive stress, the mode II fracture is more obvious, and the propagation direction of the crack in the slit direction is deflected along the direction of initial compressive stress during the crack propagation process. When the slit direction is parallel to initial compressive stress direction, crack propagation is promoted and the length of crack propagation increases, and the larger initial compressive stress, the more obvious promoting effect. •The dynamic caustic method is applied to study blast-induced crack.•The blast-induced crack propagation behavior in deep rock mass is studied.•The slit charge blasting in different slit direction is explored.•The law of crack propagation under different compressive stress is summarized.