Study Of Deformation Regularity Of Overlying Strata In Goaf Under Different Mining Time?Spatial? Sequence Based On FLAC^3D

Roof cracking,collapse and caving caused by large deformation of wall rock occur frequently in the goaf of coal mine.After a certain degree of ground subsidence caused by the deformation of the goaf,the moving basin will be formed on the surface,which causes the surface cracking,the depletion of ground water,the cracking or collapse of the wall of the surrounding buildings,which seriously endangers the safety of the lives and property of the miners and the surrounding residents.Therefore,it has important practical significance and economic significance to study the influence rule of the surface and roof deformation in goaf.This paper takes 2 coal,4 coal,7 coal,15 coal and 19 coal seam of Bei Bu mining area in LaiWU as an exaIple.Based on the theoretical analysis and FLAC3D numerical analysis software,the deformation law of the goaf under the conditions of different mining order,differentmining method,different groundwater level and overlying strata is simulated,and the typical cross section and surface deformation law of X direction and Y under different influence factors are obtained.The contents and main conclusions of the article are as follows:(1)By summarizing the characteristics of surface deformation caused by different coal seam dip angles,we get the difference of deformation characteristics between horizontal strike coal seam and inclined coal seam.Based on probability integral method,combined with the mining practice of Bei Bu coal mine,we estimate the surface deformation caused by coal mining and its influence area.(2)Through the FLAC3D numerical simulation software,the influence of different mining sequence,different mining method,different overlying strata and groundwater level change on the goaf deformation is analyzed and the surface deformation law under different mining method is revealed,and the optimum mining mode under the condition of mining deformation and mining convenience is obtained by sensitivity analysis.By changing the properties of overlying strata under the same mining conditions,the influence degree of overlying strata properties on the surface deformationisanalyzed.The influence of roof overlying rock properties and surface deformation law is larger than that of the bottom slate,and the quality of the rock layer is negatively related to the most large deformation of the ground surface and the size of the influence range.The influence of pore water pressure on the overlying strata and surface deformation in the goaf under different groundwater level is studied.It shows that the coal seam mining caused by the coal seam mining is bigger when the groundwater level is higher,and the surface deformation caused by the coal mining is smaller when the groundwater level drops,and the influence of the groundwater on the surface deformation is also obtained.(3)Based on the finding the influence of different mining sequence,different mining method,different overlying strata and the change of groundwater level on the deformation of the goaf,the corresponding control optimization measures are put forward in order to ensure the safe mining of coal resources according to the four factors.