Study on the mechanism and preliminary application of efficient directional rock breaking using a coal-based solid waste non-explosive expansive agent

In search of a safe and efficient method for fracturing coal and rock masses without using explosives and with controllable crack propagation direction，this study proposedan efficient directional rock-breaking technology utilizing a coal-based solid waste non-explosive expanding agent，i.e.，instantaneous expander with a single fracture surface(IESFS). First，directional rock-breaking experiments with an IESFS were performed with the aid of a self-developed experimental system. Besides，the damage-displacement evolution in the rock-breaking process of the IESFS was studied through numerical simulation. Furthermore，the IESFS was applied to directional roof fracturing in an underground coal mine. The research findings are as follows：(1) The IESFS utilizes an electrical current to activate the fuse，which in turn triggers the coal-based solid waste expanding agent to generate high-pressure gas within 0.05–0.5 seconds. Such high-pressure gas serves to efficiently break the rock. (2) Conventional blasting generally induces rock fracturing in a “line-to-plane-to-solid” pattern. In contrast，the IESFS fractures the rock in a “point-to-line-to-plane” pattern，that is，it exerts forces at a point，initiates rock fracturing on a line，and complete rock fracturing on a plane. (3) When used to fracture concrete specimens，the IESFS induces the formation of a high-pressure gas jet with concentrated energy at points，enabling precise control over the direction of fracture propagation and the number of fractures. (4) The damage in the cutting direction is significantly greater than that in the non-cutting direction，the former being 7.92 times greater than the latter. (5) After the IESFS is applied to in-situ fracturing of the roof，the directional roof cutting effect was superior. Additionally，its cutting rate is 11% higher than that of conventional shaped charge blasting，which is indicative of its more powerful performance. The research findings are expected to provide valuable insights and references for exploring novel non-explosive directional rock-breaking methods.