Research and application of surrounding rock support technology for roadways in extremely close range coal seam goaf

In response to the difficult problem of deformation control in the extremely close range coal seam roadway of Wuhushan Coal Mine, the distribution of rock structure and in-situ strength of surrounding rock, as well as the distribution law of in-situ stress field, are analyzed. The deformation characteristics and influencing factors of the surrounding rock in the extremely close range coal seam roadway are studied. Theoretical calculation and numerical simulation analysis are used to determine the depth of floor failure and stability of surrounding rock after upper coal seam mining. The deformation and failure mechanism of the extremely close range coal seam roadway is revealed, and corresponding deformation control techniques and schemes are proposed. Industrial tests are carried out underground. The results show that the deformation of the extremely close range coal seam roadway in Wuhushan Coal Mine is mainly manifested as roof subsidence and shoulder compression of the roadway. The maximum horizontal principal stress of the mine is at an angle of 43.0°-76.1° with the roadway, which is not conducive to the stability of the roof and floor rock layers. The content of expansive clay minerals in the lower coal seam roof rock layer is over 50%, which exacerbates the expansion deformation of the roof rock layer. The maximum depth of damage to the floor after upper coal seam mining is 28.1 m, which is much greater than the spacing between coal seams. The coal seam roadway is located very close to the overlying residual coal pillar high stress zone, and the surrounding rock is in a stress reduction zone as a whole. The lower coal seam roof rock layer still has good integrity and anchoring characteristics. Improving the initial support strength of the roadway and maintaining the stability of the surrounding rock is the key to controlling the deformation of the surrounding rock in extremely close range coal seam roadway. Based on this, reasonable pre tensioning parameters for anchor bolts are determined, and a high prestressed anchor bolt support and active passive support scheme for scaffolding are developed. After the application of underground engineering, the deformation of the surrounding rock of the roadway is significantly reduced compared to the original support roadway, with a maximum displacement of 70.8 mm for the two sides and 104.5 mm for the roof and floor. This indicates that the use of high prestressed anchor bolt support and active passive support for scaffolding can effectively control the deformation of the extremely close range coal seam in Wuhushan Coal Mine.