Research on optimization of blasting parameters and control measures for underground metal mine access mining

In response to the problems of poor cross-section formation quality, severe overbreak/underbreak, low borehole utilization rate, and high specific explosive consumption encountered in the drift mining of a fractured underground metal mine, on-site experiments and comparative analyses were conducted on key blasting parameters including the cutting method, borehole layout, borehole depth, charge structure, and initiation network based on an investigation of the engineering geological conditions and existing blasting practices. An optimized scheme combining the double-stage same-depth sequential cutting technology with a detonating cord relay clustered initiation network was proposed. By reducing the spacing of perimeter holes and employing decoupled charging and smooth blasting techniques, damage to the surrounding rock and roadway overbreak/underbreak were effectively controlled, and a larger advance per cycle was achieved under safe conditions. The application results show that after the blasting parameter optimization, the overall specific explosive consumption decreases from 2.93 kg/m³ to 1.876 kg/m³, a reduction of 35.9 %; the total charge quantity decreases by 42.5 %; the borehole utilization rate increases from 82.1 % to 95.0 %, representing an overall improvement of 15.7 %; the daily cycle advance increases by 5.5 %; the half-wall hole trace rate remains stable above 76 %; the cross-section overbreak/underbreak is controlled within 10 cm. The research findings provide a referential engineering case and technical basis for blasting parameter design and on-site control in drift mining under similar geological conditions in underground metal mines.