Study On The Roof Safe Thickness Of Thallow Buried Room Pillar Goaf Treated By Open Pit Stripping In Guojiawan Coal Mine

Before the Shenfu Guojiawan coal mine was.consolidated,it was mined by a number of private enterprises.Due to the backwardness of the early coal mining methods,a large number of shallow-buried house pillar goafs were left in the mining area.The existence of these goafs seriously affected the healthy development of the mining area.In order to completely solve hidden dangers in the goaf area,actively respond to the environmental policies of the national and local governments,and effectively use residual coal resources,the miners decided to use the open-pit stripping technology to control the goaf.With the operation of open strip and the continuous rolling of mechanical equipment,the rock mass of the roof of the goaf often produces varying degrees of deformation and destruction.When the deformation and failure extends to a certain extent,it is very likely to cause the overlying strata to fall and collapse,which is safe to the personnel and equipment of the open air operation.The word is a great threat,so it is often necessary to determine the safety thickness of the roof,which is of great practical significance to the technology of strip stripping treatment in the goaf.The detailed geological data of GuoJiaWan coal mine is collected,and the spatial characteristics of the span and depth of the room column type goaf in the area are analyzed through data analysis and survey,and the roof stability of the room column goaf is analyzed,and the safety thickness of the roof is compared with the different theoretical analysis methods,and the rational mathematical geological model is established by using the FLAC3D software.The safety thickness of the roof of the goaf is simulated,and the reasonable safety thickness of the roof of the shallow buried house in the GuoJiaWan coal mine is finally obtained.The main research results are as follows:(1)The factors affecting the roof stability of room-bay goafs are summarized and divided into four categories:geological factors,mining factors,external factors and time factors.(2)The main failure modes of the roof of the goaf are expounded and the failure mechanism of the roof is analyzed in detail.The results show that the roof failure in the near horizontal and gentle dip goaf is mainly tensile failure,and the roof failure in the steep angle goaf is mainly shear failure.(3)Three kinds of theoretical analysis methods are used to compare the roof stability of the goaf during the strip stripping process,and the recommended value of the roof safety thickness is obtained.The safety thickness of the roof is 5.3m,the span 7m thickness is 6.1m,the span 8m thickness is 7m,the span 9m thickness is 8m,and the span 10m thickness is 9m.(4)Based of FLAC3D software,using tensile stress as the failure criterion of the top plate and establishing a void model for peeling simulation study,the results show that the safe thickness of the top plate in the 6m span empty area is 6m;the safe thickness of the top plate in the 7m span empty area is 8m;8m span The safe thickness of the top plate in the empty area is 10.5m;the safe thickness of the top plate in the 9m span empty area is 12.5m;the safe thickness of the top plate in the 10m span empty area is 15m.The above research not only has important application value for comprehensive treatment of hidden dangers in goaf of Guojiawan coal mine and safe production of mines,but also provides a very important theoretical basis and reference value for the open strip treatment of room and pillar goafs in similar mines.