Rock Fracture Mechanism and Engineering Application of a Special Cut-Blasting Method with Loading Explosives at the Bottom of an Empty Hole

Abstract

In response to the challenges encountered during deep-hole straight-eye barrel-shaped slot blasting for tunnel excavation, where it is difficult to discharge fragmented rock and achieve high single-cycle footage, an enhanced throwing technique at the bottom of the hole is proposed. This technique builds upon traditional segmented charging technology and is applied at the Xingshan underground iron mine of Shougang. This method, modeled using the smoothed particle hydrodynamics–finite-element method (SPH-FEM), assesses improvements in rock particle dynamics, ejection speeds, and slot volumes compared to conventional approaches. The analysis reveals that traditional segmented charging structures in the slot lead to collisions and compressions of fragmented rocks during the detonation of the upper section, hindering the ejection process and impacting the blasting results of the lower section. The enhanced scheme significantly boosts the ejection speeds of the lower section’s fragmented rocks, with peak velocities increasing by 76.9%–86.6%, and final ejection speeds rising by two to eight times. It also effectively mitigates issues of midsection clogging, resulting in an 11% increase in slot volume. Field tests demonstrate that this innovative method achieves an average slotting advancement of 3.43 m and a borehole utilization rate of 92.7%, marking an 11.6% improvement over traditional methods. These findings provide crucial guidance for optimizing similar mining operations.