Study on Optimization of Waterproof Coal Pillar in High Angle Normal Fault Floor

In order to avoid the waste of resources and reserves caused by excessive width of waterproof coal pillar, the method combining theoretical analysis and Flac 3D numerical simulation is used to theoretically calculate the width of coal pillars along the floor and along the seam of a F 14 high angle normal fault in a mining face, and the mechanical model for fault layer activation is established and analyzed. In order to optimize the width of coal pillar, the fault zone and the top of Ordovician limestone aquifer are transformed by grouting through the construction of ground area treatment. The results show that the F 14 high-angle normal fault does not conduct (contain) water, but there is a possibility of fault activation. With the continuous advance of the working face, activation occurs in the fault zone. When the width of the coal pillar is less than 40m, cracks in the fracture zone of F 14 fault continue to develop and finally connect with each other to form a good water diversion channel. The Ordovician limestone water in the lower wall of the waterproof fault on the roof and floor of the coal seam rises along the fault fracture zone, threatening the safe mining of the working face. Meanwhile, the theoretical formula is verified, and the width of the waterproof coal pillar is initially determined to be 40 m. The grouting transformation of the fault zone and the top of the Ordovician limestone has improved the integrity of the fault water barrier and relieved the threat of floor water damage to the working face during mining. It is considered that F 14 is feasible to liberate the fault waterproof coal pillar. The research results have important reference significance for the liberation of coal resources in the hanging wall working face of high angle normal faults, avoiding waste of resource reserves, improving economic benefits and mining efficiency in mining areas, and provide countermeasures for the tension in coal mine production areas.