Study On Prevention Mechanism And Application Of Water Inrush From The Floor Of Fully Mechanized Coal Mining With Paste Filling In Coal Seams With High Confined Water In Short Distance

With the development of coal resources going deep,the distance between the coal seam and the confined aquifer of the Ordovician limestone formation gradually decreases,making the water inrush from the coal seam floor increasingly frequent.In order to utilize solid wastes as resources,better protect the ecological environment of the coal mine,and further improve the safety production conditions of the mine,the paste filling mining is now widely used in China,because the filling body formed by mining can well support the upper overburden,forming a complete support system.This system can improve the resource recovery rate without removing the coal,and can also control the surface subsidence during mining.For coal mining above confined water,this system can well protect groundwater resources from being damaged.This thesis adopts the method of combining theoretical analysis,numerical simulation and field measurement to carry out the basic theoretical research on the engineering background of safe mining of coal resources under the conditions of close proximity and high confined aquifers in typical mining areas,and has achieved the following main research results:(1)This thesis studies the distribution and propagation law of the stress in the floor of the filling coal mining on the close high confined aquifer,analyzes the failure characteristics of the floor rock mass under the participation of the paste filling,and calculates the failure depth of the floor of the paste filling working face on the basis of the equivalent mining height theory and the equivalent roadway theory.(2)The interaction relationship between the filling body and the composite waterproof key layer of the floor of the working face is explored,the structural mechanics and seepage dynamics model of the waterproof key layer of the fully mechanized mining floor filled with paste in the coal seam with close high confined water is constructed,the mechanical characteristics of the waterproof key layer of the floor are analyzed,and the mechanical criterion of water inrush from the floor of the coal seam is given based on the filling body,seepage stress coupling,The criterion of nonlinear seepage instability in the key waterproof layer is obtained,and the quantitative relationship between the filling rate and the structural stability of the key waterproof layer of the floor and the stability of the seepage system is studied in combination with a typical mining area project case.(3)The beam mechanical model of the key waterproof layer in the bottom of the fully mechanized mining face with paste filling in the seam above the high confined water is constructed,the filling process parameters and the formula for checking the safety thickness of the key waterproof layer in the bottom are determined,the formula for evaluating the safety factor of the bottom of the paste filling working face is given,and the safety evaluation method and evaluation process of the key waterproof layer in the bottom of the paste filling working face are proposed.(4)The FLAC3D numerical calculation model of paste filling in fully mechanized mining of coal seams with high confined water is established.The effects of filling step distance,filling strength and filling ratio on stress transfer and plastic failure during coal seam mining are studied,as well as the failure characteristics of upper floor under confined water.According to the geological conditions of 11607 working face in Daizhuang Coal Mine,the paste filling material ratio,filling system technology and filling system capacity are designed.By using the floor drilling subsection water injection method,the floor damage depth of the filling face was measured to be 3-5 m,which realized the safe mining of the coal seams above the confined water in short distance.This thesis has 82 figures,24 tables and 141 references.