Research On Instability Law And Control Of Surrounding Rock Of Roadway Under Repeated Mining Of Close-range Coal Seam Groups

Aiming at the technical problem of roadway surrounding rock stability control under repeated mining of short distance coal seam group,taking Shengan coal mine in Jinsha County of Guizhou Province as the background,this paper studies the law of roadway surrounding rock instability under repeated mining of short distance coal seam group by combining field measurement,theoretical analysis,numerical simulation,similar simulation and field engineering practice,Finally,the supporting scheme is put forward to support the roadway.The main conclusions are as follows:Through on-site sampling and data observation,combined with indoor test and borehole observation,it is determined that the overall roof of 10905 return air roadway is not broken,but the overall bearing capacity is weak,the roadway roof and coal pillar side are obviously broken in different zones,the surrounding rock of the roadway presents the characteristics of asymmetric evolution of surrounding rock cracks,and the deformation of the left and right sides of the roadway is asymmetric.Through the elastic-plastic theory and slip line field theory,the floor failure depth caused by the upper coal seam mining is analyzed,and the floor failure depth caused by the mining of No.6 coal seam is 4.56 m.Through numerical simulation,it is concluded that the deformation mechanism of surrounding rock of roadway under goaf without residual coal pillar in close coal seam is different from that with residual coal pillar.The stress concentration caused by no residual coal pillar in No.9 coal seam working face and roadway makes No.9 coal seam under goaf in a low stress environment,and the mining height of No.9 coal seam working face is small,The influence of adjacent working face on overlying follow-up strata is less than that of thick coal seam.After mining in the adjacent working face and this roadway,the overall vertical stress of the reserved roadway and the coal pillar roof has little change,and the deformation of the surrounding rock of the roadway increases with the increase of mining times,especially the horizontal displacement of the coal pillar side of the roadway changes greatly,and the actual damage degree is the largest.According to the similar simulation test,the strata behavior law of the lower coal seam is different from that of the overlying strata movement.Affected by the boundary coal pillar of the goaf of the upper coal seam,under the disturbance of the next mining of the lower coal seam,the overlying strata of the lower coal seam are more likely to be unstable and broken in a small range,with smaller weighting step and frequent weighting.Through the above research,the asymmetric bolt mesh cable + i-steel support scheme is proposed.The feasibility of the support scheme is verified by numerical simulation and field engineering practice.The maximum displacement of roof is 326 mm,the maximum displacement of coal pillar is 225 mm,and the maximum displacement of solid coal wall is 201 mm.The deformation on both sides of the roadway is asymmetric distribution.However,the deformation of the whole surrounding rock is within the controllable range,and the deformation and instability of the surrounding rock are not occurred.