Blasting Parameter Optimization of Underground Fan-shaped Medium-deep Holes based on Crater Test

Under the deep geostress environment, ore-rock masses exhibit distinct mechanical properties and fragmentation characteristics that markedly differ from those observed in shallow deposits. To optimize the blasting parameters for fan-shaped medium-deep holes in the deep stope of Tonglushan Copper-Iron Mine, crater blasting tests were conducted at the 9428 stope of the-485 level, following a comprehensive analysis of the ore-rock mechanical properties at this depth. Optimized medium-length hole blasting parameters were systematically derived from a thorough analysis of crater morphology and specific explosive consumption characteristics, with subsequent industrialscale trials confirming their technical validity and operational feasibility. The research findings demonstrate that the rock mass integrity coefficient of the skarn in the 9428 stope of the-485 level at Tonglushan Mine measures 0.39, classifying it as relatively fragmented according to the Standard for Engineering Classification of Rock Mass. Singlehole carter blasting tests revealed optimal parameters including: charge center burial depth（0.400 m）, critical burial depth（0.898 m）,strain energy coefficient (1.69 m/kg^1/3),optimal burial depth ratio（0.445）, optimal crater radius（0.461 m）, and optimal crater volume（0.014 m）. Subsequent double-hole and inclined bench crater tests determined an optimal hole spacing of 0. 809 m and a minimum crater burden of 0.740 m. Applying blasting similarity theory to production-scale fan-shaped medium-deep holes（64 mm diameter）, recommended parameters include: hole bottom spacing（1.3 ~ 1.6 m）, hole mouth spacing（0.8 ~ 1.3 m）, and row spacing（1.1 ~ 1.4 m）.