Model experimental study on the effects of in situ stresses on pre-splitting blasting damage and strain development

In the process of drilling and blasting in deep underground engineering, in situ stress is usually considered as an essential factor for blasting parameter design. To explore the effect of the in situ stress value and direction on pre-splitting blasting (PSB), the blasting failure characteristics of a rock mass under different stress conditions are experimentally simulated by applying vertical and horizontal uniaxial pressures and blasting load to gypsum specimens. First, fractal theory is implemented to study the influence of uniaxial pressure on crack propagation and distribution. Second, based on the digital image correlation method, the development of strain in the surrounding rock is revealed. Finally, the damage distribution characteristics of the specimens after blasting are studied by using the acoustic wave detection. The results indicate that the value and direction of uniaxial pressure have a significant influence on PSB. Hence, when the direction of uniaxial pressure is parallel to the blasthole layout, the crack path is relatively straight. The damage of gypsum specimens decreases with the increase in uniaxial pressure. The attenuation amplitude of the peak strain in the parallel direction with the distance is much smaller than that in the vertical direction. When the direction of the uniaxial pressure is perpendicular to the direction of blasthole layout, the damage of specimen after blasting is substantial and is not conducive to the formation of cracks.