Instability features of mining roadway in deep-thick coal seam and progressive bolt-mesh-cable-grouting support technology
With the increase of coal mining depth,the problems of large deformation,supporting diffi-culties,and repeated repairing of mining roadway are prominent.An investigation of loose-broken zones of surrounding rock in mining roadway was conducted using borehole scopes to assess the supporting problem of deep-thick coal seams,the loose-broken range of the mining roadway was 2.8-3.7 m,which belonged to a large loose circle with unstable surrounding rock.The similar material modelling test and the FLAC3D numerical simulation analysis were carried out to investigate the mining stress distribution law and roadway instability characteristics in deep-thick coal seam.The transfer law of the mining-induced stress,the deformation field of surrounding rock,and the stress field and plastic zone of mining roadway were revealed.The stopping line of the working face in the deep coal seam was about 50 meters away from the roadway,allowing the mining-induced stress to reduce its effects on the roadway stability beneath the coal seam.As a result of theoretical analysis and model testing on the bearing char-acteristics of the supporting structure,a bolt-mesh-cable-grouting progressive support system was devel-oped to support mining roadways in deep-thick coal seams,and it was successfully applied to the Guotun Coal Mine's main roadway with mining level of-808 meters.The mining pressure monitoring in the field indicated that the deformation of surrounding rock tended to be stable after about 60 days.The max-imum subsidence of roof,the maximum floor heave,and the maximum rib-to-rib convergence were 71-75 mm,63-69 mm,and 94-118 mm,respectively.There were no accidents,such as roof collapse or rib spalling,and good supporting effects were obtained.
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