Study on the novel technique of straight hole cutting blasting with a bottom charged central hole exploded supplementally

To improve the cutting efficiency in the deep hole blasting of rock roadways, a straight hole cutting blasting technique with supplemental blasting of the central hole was developed. First, the blasting mechanisms of the traditional and novel cutting methods were analysed theoretically. For the novel cutting method, the upper uncharged part of the central hole still acted as empty hole. Cutting hole blasting could eject most of the rock mass in the cutting cavity and hence produce a new free face to weaken the clamping effect of central hole blasting. Then, the residual rock mass could be fully removed after central hole blasting. Second, simulation of the new cutting mode was conducted, which visualized the stress wave forming process. Simulation results showed that the rock mass at the bottom of the cutting cavity could be predamaged by the stress wave caused by cutting hole blasting, and the high-intensity stress field generated by central hole blasting would lead to further damage to the residual rock mass. Thus, the residual rock mass could be thrown out readily. Finally, the auxiliary roadway of an iron mine was selected for the blasting experiments. After statistical analysis, due to the supplemental blasting of the central hole, the average blasting footage was increased by 0.35 m, and the average specific charge was reduced by 0.43 kg·m −3 , which validated the predominance of the novel cutting method in the deep hole blasting of rock roadways.