Study On The Evolution Law Of Water Inrush From Mining Floor

Coal mining gradually develops into the deep part.Under the conditions of high groud stress and high water pressure,the safety of coal mine floor faces huge challenges.In some mining areas in North China and South China,the thick Ordovician limestone Karst buried deep below the floor raises higher requirements for confined water mining safety technology.Based on the production conditions and hydrogeological conditions of the Tunlan Coal Mine in Shanxi,this paper uses theoretical analysis,physical tests and numerical simulation methods to deeply study the evolution rules of rock fractures and water inrush in the coal seam floor.The following tasks were carried out:The hydrogeological conditions of 8~#coal seam in Tunlan Coal Mine are summarized,and the engineering geological environment of 1132 working face of 8~#coal seam is determined.The softening effect of water pressure on the rock mass is analyzed,and the fracture surface expansion height under water pressure is calculated using the theory of fracture mechanics.Using the elastoplastic mechanics method,the mining failure depth of the floor is 23.8m,and the safe thickness of the floor is19.41m.It was further calculated that the remaining effective water-tight layer thickness t'of the floor was 8.79m,and thus the risk of water inrush from the water-proof floor of the 1132 working face was evaluated as basic safety.Seven groups of rock and soil triaxial stress-strain seepage tests were carried out.The test results fully reflected the rock deformation and deformation process under the seepage condition and the permeability change law in the high pressure environment.The test control under different conditions gave different controls The effect of factors on rock mass fracture deformation and permeability.According to the actual engineering geological conditions and similar test theory of mine production,select similar simulated materials reasonably,establish a similar model of coal mining engineering geomechanics,and simulate the generation,expansion and penetration of cracks in the floor of high-pressure water mines under deep conditions,The test simulates the real situation of mining well,and summarizes the formation and evolution characteristics of the water-conducting channel of the floor aquifer.The finite element software FLAC3D is used to simulate the mining of the 1132working face of the 8~#coal seam in Tunlan Coal Mine,and the software fluid-solid coupling module is used to establish an analysis model of large deformation in mining.The simulation results reflect the changes in the stress,strain,and plastic zone of the floor rock mass during mining,as well as the changes in pore pressure and flow velocity under the action of seepage,The dynamic changes of stress-strain and permeability of the aquifer of the mining floor are summarized.Hazard sources have a wide range of scientific meanings,and their three characteristics are also the focus of research on floor water inrush disasters.Based on the analysis of the meso-rock rock rupture risk and the macro-crack evolution law,the danger level of the water-conducting channel of the coal floor on the confined aquifer is divided into different levels,and the influence of the rock mass rupture and the dynamic changes of the fracture evolution process are used to divide the water conductivity.The dynamic danger level of the aisle realizes the comprehensive evaluation of the water inrush disaster of the mining floor.The main conclusions of the paper include:The thick alumina ash aquifer in Tunlan Coal Mine poses a great threat to the floor.The water-proof layer of 8~#coal seam in 1132 working surface is 67m thick.After the coal seam is excavated for 180m,the bottom water barrier layer is not formed,and the effective water barrier thickness is about 21m;Different indexes affecting the water inrush from the floor control the fragility of the rock mass;The stress field,displacement field,and seepage field in the bottom rock mass have changed due to mining activities.The interaction between different fields has finally led to the evolution of the bottom channel.The comprehensive analysis of the formation process of the aqueduct can effectively evaluate and predict the risk of flooding.