Research on the Technology of Long-span and Open-cut Hole Support in Secondary Excavation

In view of the problems such as the increase of coal mining depth, the increase of open-cut hole, the complex and changeable geological conditions, and the increasingly difficulty in surrounding rock support, by using FLAC^3D numerical simulation software, the long-span and open-cut hole support in 8702 fully mechanized working face in Nanyangpo Coal Mine was studied, the variation law of surrounding rock stress and displacement of the open-cut hole during the secondary excavation were analyzed. The results show that the displacement of the open-cut hole is 50% greater than the displacement of the brush-enlarged open hole, the displacement of the left side of the open-cut hole is larger than that of the right side and the right side of the brush-enlarged open hole, the displacement of the left side of the open-cut hole is greater than that of the right side. The failure mode of open-cut hole is roof tension crack, and the failure mode of brush-expanded open hole is extrusion failure of side. Based on the theory of suspension and the successful experience of other mining areas, the scheme of bolt-mesh-cable combined support is determined. Through the analysis of the monitoring results, it can be seen that the deformation of surrounding rock basically coincides with the deformation of numerical simulation under the supporting conditions. The supporting scheme can effectively control the deformation of surrounding rock and ensure the stability of the open-cut hole.