Study On Fracture And Permeability Evolution Law Of Overlying Rock At Stope Boundary

Gob water will threaten the safety of adjacent working face or mining area.In this paper,aiming at the problem of lateral leakage of water in gob of Bofang coal mine,the formation conditions of water in gob of Bofang coal mine are analyzed by using the methods of theoretical analysis,numerical simulation and field measurement.The development characteristics of lateral cracks and the evolution law of permeability in overlying rock of stope boundary are studied,and the scheme of preventing and controlling lateral leakage of water in gob is put forward,The main conclusions are as follows(1)Based on the analysis of the characteristics of aquiclude in the working face of the first panel,it is determined that the source of water in the goaf of the first panel is the sandstone fractured aquifer in the roof of the coal seam,and the amount of water in the goaf of the first panel is calculated.It is determined that the main water source of the main roadway in the third panel area is the water accumulated in the goaf of the first panel area,the secondary source is the water stored in the roof sandstone itself,and the main seepage channel is the roof sandstone itself.(2)This paper analyzes the distribution characteristics of stope boundary stress,and expounds the influence of coal seam thickness and buried depth on the development width of stope lateral fractures.The development characteristics of the lateral fractures at the stope boundary are studied.The width of the lateral fractures increases first and then decreases from the top of the coal seam roof.The maximum width is at the highest position of the shear failure area,and the minimum width is at the two ends of the working face.The development width of lateral fracture in working face is 31 m,which is 5.45 times of mining height.(3)Based on the "cube law",the fracture seepage stress equation is derived.The evolution law of overburden permeability at the stope boundary is analyzed by using the pore water pressure and seepage velocity parameters in the FALC3 D numerical simulation software.The influence of the elastic modulus of rock layer and the mining height and buried depth of coal seam on the overburden permeability at the stope boundary is studied.(4)This paper puts forward a scheme to prevent and control the lateral leakage of the gob water in the first panel,determines the parameters of the main roadway grouting in the third panel,and determines that the distance between the stoppage line of the working face in the third panel and the main roadway in the third panel is 50 m.There are 58 figures,10 tables and 156 references in this paper.