Study On Mining Damage And Water Resisting Property Of Coal And Rock Pillars In The Closed Mine Boundary Of HengYuan Coal Mine

In order to ensure the independence of water prevention and control during mine production,to ensure mine safety and not to be threatened by water hazards in the adjacent closed mine,coal and rock pillars in the mine boundary must be left between mines.However,due to the complexity of the geological conditions of the mine and coal and rock pillars in the mine boundary were destroyed by later disturbances,accidents of water bursting from the coal and rock pillars in the mine boundary still occurred from time to time.Therefore,studying the mining damage and water resisting property of coal and rock pillars in the mine boundary after the mine was closed is of great significance for evaluating the impact of the closed mine water on the adjacent production mines and ensuring the safe production of the mine.This paper taken the coal and rock pillars in the mine boundary between the Hengyuan Coal Mine and the adjacent Liuqiao No.1 Coal Mine as the research object,analyzed the mine geological and hydrogeological conditions,and used theoretical calculations,numerical simulations,and drilling exploration methods to analyzed the mining damage of coal and rock pillars in the mine boundary.On this basis,its water resisting property and stability were evaluated,which provided a basis for Hengyuan Coal Mine to prevent and control closed mine water hazards.The main results achieved follow:(1)Based on the limit equilibrium theory and the standard formula,the coal pillar damage width,the maximum damage width of the rock pillar and the height of water flowing fractured zone are calculated.According to the FLAC3D numerical simulation software,the mining damage of coal pillars with different widths was simulated,and the distribution characteristics of plastic failure,vertical stress,vertical displacement,and shear stress of the coal pillars in the mine boundary were obtained.And according to the roof failure characteristics of different coal pillar widths,three types of coal and rock pillars damage are classified:fracture connected type,fracture semi-connected type,and fractured unconnected type.(2)The results of ground drilling exploration showed that the drilling fluid leakage in the exploration hole of the coal and rock pillars were obvious,and the integrity of the drilling core was poor;the development height of the coal roof caving zone and water flowing fractured zone were basically consistent with theoretical calculations and numerical simulations.(3)Based on the monitoring of water inflow in Hengyuan Coal Mine and combined with the research results of coal and rock pillars mining damage,the water resisting property of coal and rock pillars in the mine boundary was evaluated.The results showed that the water resisting property of coal and rock pillars in the mine boundary was poor,and there was a phenomenon that the goaf water in Liuqiao No.1 Coal Mine flowed into Hengyuan Coal Mine along the coal and rock pillars in the mine boundary.(4)According to the calculation results of Terzaghi’s formula,it is concluded that the hydraulic gradient of coal rock pillars in the mine boundary was less than the critical hydraulic gradient required for the occurrence of suffusion,coal and rock pillars in the mine boundary will not suffer from seepage instability as the level of goaf water rises.Figure[32]table[6]reference[113]...