Simulation Of Floor Failure And Risk Assessment Of Water Inrush Of Pingdingshan No.10 Mine Based On FLAC^3D

The water damage in Pingdingshan No.10 mine is more serious,and it has occurred several water damage accidents since the production.No.10 mine is gas-outburst coal mine,and the gas type is extremely complex.In order to release the coal gas in advance,it is decided that the protective layer should be mined firstly.That is,0.5 m Geng-18 coal and 1.5 m mudstone,below 15 m from Ji-17 coal seam floor,shoud be mined firstly and use the mining fissures which are formed in coal seam's mining process to release coal gas.However,the exploitation of the protective layer will cause the floor water barrier damage and reduce the effective waterproofing's thickness between the coal seam and the strong water layer of the mining area-Cambrian limestone aquifer,which will increase the risk of water inrush from karst water in Cambrian limestone.The Cambrian limestone is the most important watermelon hidden danger of the protective layer in the No.10 mine.The water is rich and the recharge is sufficient.It can enter the mine through the mining fissure,the karst fissure and the fault zone,affecting the safe production of the mine.Therefore,discussing the mining failure law and water inrush mechanism of coal seam under the mining condition and correctly evaluating the risk of water inrush from floor are the urgent problems to be solved in the process of mining the lower protective layer of24130 working face in Pingdingshan No.10 mine.Based on the comprehensive analysis of geological and hydrogeological data of24130 working face in Pingdingshan No.10 mine,the FLAC^3D numerical simulation software is used to simulate the process of mining the lower protective layer of 24130mining face in No.10 mine and also the deformation and failure of the surrounding rock of the roof and floor,then determine the depth of the floor damage.For the later mining of Ji coal,the mining failure of the surrounding rock formed by the formation of Ji coal is simulated at different intervals after the exploitation of the protective layer,and the failure characteristics of the surrounding rock are summarized.In order to simulate the bottom water inrush problem in mining the lower protective layer under the condition of the existence of hidden conductive water,the fluid-solid coupling simulation model is established,which simulates the process of water inrush of karst confined water from fault and mining failure to coal mine.The numerical simulation results are combined with the risk assessment of the limestone confined water inrush of the working face's lower protective layer to calculate the water burst coefficient and comprehensively evaluate the risk of water inrush in confined water.The results show that:?when the protective layer of 24130 working face is mined individually,the maximum stress of the bottom rock mass is continuously increased to 86.89 MPa and then stay stable,the maximum vertical displacement of the roof and bottom rock mass is respectively 40.26 cm,9.48 cm,the depth of the damage of floor is 24.5 m;?Considering the depth of the bottom plate,the water inrush coefficient of the limestone water is 0.12 MPa/m,which exceeds the critical water inrush coefficient of the tectonic fault block;The karst water will break through waterproof floor into the mine through mining fissures or permeable fracture zone.?When the Ji coal group is superimposedly mined,the mining damage cracks of the bottom plate and the roof are penetrated when the protective layer is mined.The depth of destruction of the protective floor is still 24.5 m,and the height of the roof failure is stabilized at 53.8 m with the advance of the working face.?The results of fluid-solid coupling simulation show that the pressure destruction zone of bottom plate eventually penetrates with the pressurized water guide belt and becomes the channel through which karst water enters the mine with the advance of the working face and the passage of time.