Research On Surrounding Rock Control Technology Of Underlying Roadway In Remaining Coal Pillar Of Jushan Coal Mine

The resource of remaining coal pillars left from the thick coal seam is rich and precious,becoming a hotpot development issue for the recovery and utilization of resource-exhausted coal mines.Recovering the resource of coal pillars and controlling the deformation of surrounding rock not only are of great significance for improving the quantity of coal recovery,but also for ensuring production safely and efficiently.In this study,based on the local geological condition of No.3 coal seam in Jushan Coal Mine,from the overall perspective of recovering remaining coal pillars and controlling the stability of surrounding rock on the underlying roadway,some measurements were applied to researching the technologies about recovering coal pillars and controlling surrounding rock of the roadway,such as the theoretical analysis,simulation testing and field measurement.The specific research results are as follows:(1)The No.3 coal seam of Jushan Coal Mine is complicated in occurrence condition,while is simple relatively in geological structure and hydrological condition.On this basis,through collecting the samples of coal and rock in the area of main haulage roadway under residual coal pillars in ZF302 mining face and testing the physical and mechanical parameters of coal and rock,the uniaxial compressive strength,tensile strength,shear strength and other physical and mechanical characteristics of coal seam and roof strata were mastered.(2)The rock formation detection drilling camera system was used to carry out field test of the surrounding rock loose circle on the ZF302 remaining coal pillar working face under the transportation roadway.And the test result indicated that the loose circle in left side and right side of the underlying main haulage roadway surrounding rock ranged from 0.55 to 0.65 m and 0.45 to 0.60 m,respectively,as well as from 1.20 to 1.35 m in roof.Therefore,it basically belongs to a small loose circle that provides parameters for supporting the roadway.(3)The form of pillar load was determined in accordance with the influence distance of abutment load being 35.14 m in ZF302 coal pillar,to analyze the transfer characteristics of coal pillars acting on the floor.The results show that the underlying main haulage roadway in ZF302 mining face with residual coal pillars could be strongly affected by mining-induced stress,reaching the maximum coal pillar floor damage depth of 15.22 m.Therefore,these results are beneficial for reinforcing theunderlying main haulage roadway surrounding rock in ZF302 mining face with residual coal pillars.(4)The numerical calculation model of remaining coal pillar recovery and surrounding rock deformation of the underlying roadway was established.The results show that the peak of advanced stress was about 20 m,as well as the peak of vertical stress and horizontal stress were 20 MPa and 5 MPa,respectively,in the mining process of ZF302 coal pillar mining face.Besides,the vertical stress peak of the two sides and the roof in the underlying main haulage roadway of ZF302 mining face were 19 MPa and 13.6 MPa,respectively.The left-right side and roof-floor convergences of the underlying main haulage roadway were 180 mm and 150 mm,respectively.After mining production,the area of plasticity was two times larger than that of before mining.(5)The roadway layout of ZF302 coal pillar mining face and corresponding mining technological parameters were determined.Some technical schemes of surrounding rock for the underlying haulage roadway was proposed,such as backfilling and bolt-cable supporting,to strengthen the support of underlying haulage roadway surrounding rock with the different vertical distances from the floor of ZF302 mining face.The actual results indicate that the maximum yield load of supports in ZF302 coal pillar mining face was 28.59 MPa.Eventually,the left-right side and roof-floor convergences of the underlying main haulage roadway were 135 mm and 80 mm,respectively,as well as the top separation distance of the roof was about 30 mm.That can control efficiently the deformation of underlying haulage roadway in process of recovering the coal pillar.