Numerical simulation analysis of pressure relief effect under the combined action of horizontal slotting and roof fracturing

For the large coal pillar stress concentration degree and the large roadway deformation in the process of mining in multi-lane layout face, to reduce the stress level of coal pillar, change the stress distribution ratio and transfer the stress concentration area to the deep part of solid coal, a dual method of horizontal slotting and roof fracturing is used to weaken the pressure relief of coal pillar and roof in the process of multi-roadway mining. Based on the analysis of the fracture structure and stress distribution of the side roof of the coal pillar retaining roadway and the pressure relief mechanism of the coal pillar under the combined action of horizontal cutting and roof fracturing, the numerical simulation analysis is carried out for the No.2 well of Nalinhe Coal Mine. The results of analysis indicate that when the slotting spacing is 2 m and the coal pillar near the roadway is reserved at 5 m, the pressure bearing range of coal side is mainly in the range of 1-15 m, which is about 30% lower than that without any pressure relief measures; after adopting the scheme of ultra-high pressure hydraulic cutting + fracturing and roof breaking, the stress on the side of protective coal pillar is greatly reduced, which is basically in the original rock stress state, without stress concentration, and the stress is 47% lower than that without any pressure relief measures.