Study on water retention mining of thick coal seams under aquifers of high thickness

In view of the problem that it is easy to cause the fracture of the upper aquifuge in the process of large mining height mining, which leads to the water gushing from the aquifer to the underground and poses a threat to the safety of mine production, taking the 4301 large mining height working face in the third panel of Liuzhuang Coal Mine as the engineering background, the theoretical analysis, numerical simulation and upward hole water injection leakage measurement method are used to analyze the development characteristics of the overlying rock aquifer and aquifuge in the working face, and the main aquifer and aquifuge in the overlying rock layer are determined.In the auxiliary transport roadway, the range of fracture development in the process of coal seam mining is measured by the method of underground inverted hole water injection, and the development height of fracture zone in the process of thick coal seam mining is calculated by empirical formula.The FLAC^3D numerical simulation software is used to simulate the mining process of coal seams with different mining heights under the same geological conditions to determine the height of fracture development and determine whether it is connected with the aquifer.Through the above research, different mining heights lead to differences in the development height of fractures.Under the premise that the fracture-mining ratio of working face is 27.9-31.6, when the mining height less than 5.5 m, the separation zone appears in the overlying strata, and the mudstone of Anding Formation bends and sinks during the mining process, which makes some fractures compacted and closed, and the water retention effect is good.When the mining height is 6.0 m, the overburden fracture runs through the water-resisting layer of Anding Formation and develops to the aquifer of Yijun-Luohe Formation.The water inflow of the working face increases, and the working face has potential safety hazards.Finally, it is determined that when the mining height of Liuzhuang Coal Mine is 5.5 m, it can maximize the mineral benefits and ensure safe production.Through the field application of 4303 working face in Liuzhuang Coal Mine, no water inrush disaster accident occurred, which ensured the safe production of the mine and verified the scientific rationality of this study.