Analysis Of Surface Deformation In Thick Coal Seam Mining Under Super Thick Conglomerate Strata

In order to study the law of surface movement of coal mine with gravel and to do a good job in mine safety production and the protection of surface buildings in mining area,the monitoring of surface deformation should be carried out in mining area.This paper is based on the following four aspects of a coal mine in Shandong.in view of the problem of obtaining the parameters of surface rock movement in a coal mine in Shandong province,through the design of the ground surface of 107105109103113 fully mechanized mining face and the installation of rock displacement monitoring station,The Trimble 5800 ? GPS receiver is used for static relative positioning in ground control survey.After field survey,the coordinates of ground control points are obtained by baseline calculation with HGO data processing software.There are three trending lines and four inclination lines on the surface of the earth surface.The plane coordinate transfer is carried out by Nikon DTM-352N total station and the elevation survey is carried out by Trimble DIN103 electronic level.According to the measured data,the surface movement parameters are calculated.According to the monitoring data,the subsidence curve of the monitoring points is plotted with MSDFVS software to get the surface movement angle values of the mining face,including the upper and lower comprehensive moving angles,the maximum subsidence angle and the upper one.The comprehensive boundary angle of the downhill provides a reference for the calculation of the breaking distance of the next rock strata.In this paper,on the basis of conventional observation methods,the deformation analysis of surface subsidence in mining area is carried out by using D-InSAR technology,and the deformation monitoring of surface subsidence in mining area is carried out.In other words,11 SAR images of November and April were selected and 10 interferometric pairs were formed.The SAR images used are SLC images of VV polarization in wide-amplitude mode measured by Sentinel-1 A satellite lift-orbit interferometry,and DEM are SRTM-3 DEM with resolution of 90m and POD precise orbit ephemeris with positioning accuracy less than 5cm.The phase unwrapping and geocoding of 10 interferograms in SARscape were carried out,and the corresponding surface deformation maps were obtained by changing the apparent line direction value to the vertical direction value.In order to compare the surface subsidence above each working face,the surface deformation map is imported into the Google Earth software,which contains the information of the surface observation line and the information of the underground working face,and the subsidence value is extracted.Through the comparison,it is found that the surface settlement of the coal mine tends to increase abruptly at the H13-H27 monitoring point on the H-line for a period of time.According to the data of TD-1#,TD-2?,TD-3?and other data,the existence of key strata in this mine stratum is determined and analyzed,and the fracture and stress of key strata are analyzed based on the theory of key strata.The position of the key layer of the coal mine is judged by the stiffness condition and the strength condition,and the breaking distance of the gravel rock is obtained by combining the surface movement angle obtained by the conventional monitoring method.The numerical model of five working face excavation is established by using FLAC3D numerical simulation software through the steps of meshing,defining Mohr-Coulomb criterion,defining material parameters,loading boundary conditions,and solving the equilibrium of model initialization.In the process of excavation,the load on the gravel rock,the plastic damage to the model and the change of subsidence are analyzed for each 100 m excavation.The results show that the critical layer of conglomerate begins to fracture but not broken when only one working face is excavated.When two working faces are excavated,the critical layer of conglomerate appears to break and the breaking distance is consistent with the calculated value.When mining three working faces,the broken range of gravel strata increases,when mining four working faces,the range of rock failure reaches 80%of the model,and when five working faces are mined,the degree of failure of conglomerate rock is basically unchanged.Through studying in this paper,it can protect the mining design and production of mining area,prevent the sudden subsidence of gravel rock,make full use of the key layer of conglomerate to control the deformation of the surface,and provide the theoretical basis for solving the problem of coal pressure under the village.