Research On Mining Failure Law And Mining Upper Limit Of Overlying Strata Under Thick Topsoil

The failure deformation law of overlying rock and soil under thick loose layer is directly related to the determination of mining upper limit,which is of great significance for safe and stable production.Based on the failure deformation of roof overlying rock and soil by short-range coal seam under the thick loose layer,taking the third coal seam in the first mining area of Lilou Coal Mine as a case study,the following conclusions are obtained through the lithology,structural characteristics and water-bearing conditions of overlying rock and soil.(1)Based on the analysis of the height development law of water-conducting fissure zone by means of empirical formula,measured comparison and multi-factor analysis,the failure deformation law of roof and overburden rock(soil)of the 3rd coal seam under the mining condition of Lilou mine field is studied.The height and development range of the water-conducting fissure zone is estimated to be about 8～19times thick.(2)The failure and settlement law of overburden rock and soil in the area are studied and analyzed by means of physical model test of similar materials and numerical simulation analysis.The results show that the failure tendency of overburden rock and soil in coal seam mining shows the same tendency and the coincidence degree is high.During the mining process of the 3rd coal seam in the research area,the greater the advancing distance of the working face,the higher the development height of the mining fissure,to about 350 m in the working face,and the fracture height reaches stable,with the guide height of 130.2m above the roof and the final fracture ratio of 18.6 times.(3)Based on the prediction of the development height of the fracture zone,the relationship between the 3rd coal seam and the occurrence elevation of bedrock surface is analyzed.The vertical height of the coal seam roof waterproof coal pillar is 158.0m.Considering the infiltration zone and the thickness of the protective layer,the upper limit of coal seam exploitation in the north of the first mining area is-601.27 m.Figure [45] Table [19] Reference [72]...