Spatial-Temporal Evolution Mechanism And Control Technologies Of Surface Mining Cracks In Shallow Thick Coal Seam Mining

The occurrence conditions of shallow burial depth,thin bedrock and thick coal seam in the western mining area and the characteristics of fragile surface ecology,the instability movement of overlying rock strata in the coal mining process has a large influence range,and the surface movement and destruction are quite severe in the mining process,resulting in a large number of surface mining fractures in the mining process.Mining ground cracks in coal mining subsidence areas are easy to cause soil erosion and soil erosion,which seriously affects the problems of mining land reclamation and ecological restoration.Based on the field investigation and theoretical analysis,numerical calculation,the combination of the shallow thick coal seam mining stope surface crack evolution mechanism,the dynamic development process and the main influence factors are studied,based on the damaging to crack control of the shallow thick coal seam security green mining technology,for shallow buried deep thin bedrock mining thick coal seam mining provides a theoretical basis for the safety of the green.Based on the theory of key stratum of strata movement,the east of typical coal mine rock god makes a statistic analysis on the geological occurrence conditions,determine the thickness of coal seams in the study area,the critical layer thickness,ratio of key layer of the deep and thick coal with key layer of the scope of the ratio of the distance from the coal seam,and the shallow thick coal seam occurrence characteristics of overburden rock classification.Based on the actual engineering geological conditions,a 3DEC numerical model was established by using the orthogonal experiment method to simulate and analyze the instability deformation of overburden and surface in the mining process of shallow and thick coal seam,and the instability movement and fracture law of overburden strata were obtained.By analyzing the range of overburden subsidence and horizontal displacement,the influence degree of different factors on the overburden deformation at different strata is obtained.According to the displacement data at different propulsion distances,the opening and dislocation of the surface cracks of the model are obtained.Based on the analysis of the openfault data,the effects of various factors on the ground fracture are obtained.According to the model displacement cloud map,the evolution law of mining-ground fractures under shallow burial is obtained.The distribution range of surface fractures is determined by calculating the mining fracture Angle of shallow and thick coal seam.By analyzing the displacement cloud map of the surface view Angle,the law of the movement and change of the surface fracture zone is obtained.Based on the morphology and distribution characteristics of surface mining fractures,the formation conditions and evolution rules of destructive fractures are obtained.From the perspective of preventing damaging fractures,the controlling mining techniques such as filling mining,partial mining,intermittent mining and out-of-bed grouting are introduced.Control mining technology can ensure the occurrence of safety accidents such as roof slide and unstable pressure frame in thick coal seam mining and effectively reduce the surface subsidence,which provides technical guarantee for safe production.From the perspective of the treatment of damage type ground fracture,the concept of new material ground fracture filling treatment technology is introduced,which provides a certain theoretical basis for the green mining of thick coal seam in shallow buried deep thin bedrock mining area.