Experimental Research on Cutting Blasting into Cavity from Blind Raise

In order to solve the problem of high labour intensity, low work efficiency and poor safety in the drilling of blind shafts using hydraulic rock drills in the Dahongshan Iron Ore Mine, it is proposed to adopt the one-time well-forming technology of blind shaft deep hole blasting. A trenching test was carried out on the test blind patio, and the compensation factor for the area to be blasted was calculated and the trenching hole layout was designed based on the mechanism of rock breaking action and cavity formation theory for undercutting. The detonator was used on site to initiate the detonation and a 3D laser scanner was used to scan the post-detonation cavity to study the variation of its area with depth. The test results show that: after detonation of all the rocks to be blown out of the slot cavity, the cross-section is lotus-shaped, the wellhead area is flat, the wall is clear; after the explosion of the slot depth of 9.64 m, in the near hole 0 ~ 2.5 m, the slot cavity cross-sectional area of more than 0.3 m², in 3 m ~ 8.5 m from the hole between the slot cavity cross-sectional area of 0.2 m² fluctuations, the bottom of the slot cavity cross-sectional area of 0.04 m²; the overall pattern of change in the area of the cavity is from the near orifice to the bottom of the cavity, with the increase in depth of the cavity, the area first gradually decreases, then tends to fluctuate above and below a certain value, and finally decreases rapidly until the bottom of the cavity. This provides reference for the subsequent blasting of the blind shaft in one pass.