Study on retaining technology of retracement channel in large mining height working face of thick coal seam with shallow-buried depth

In view of the problem of retaining the retracement channel in large mining height working face of thick coal seam with shallow-buried depth, the range of plastic zone, elastic zone and the stress distribution in the zones under the influence of abutment pressure in front of the coal wall of the working face are analyzed theoretically based on the comparison of the advantages and disadvantages of the three methods. During the extension process from the surface layer of the coal wall to the deep part of the coal body, the value of the abutment pressure in the leading region firstly increases to the peak value in the exponential function form, and then it finally decreases to the stress state of the original rock in the form of negative exponential function, and the pressure attenuation area in front of coal wall is the best position to arrange the retracement channel. Field application shows that the peak value of advanced abutment pressure is 10.02 m in the front of coal wall at Daliangwan Coal Mine. A further 5 m is extracted to pass the pressure duration after the last periodic weighting of the working face before the designed stop-mining line, and the self-cutting retracement channel process with two-machine coordination is adopted in the abutment pressure attenuation area. The stability of channel roof could be effectively maintained by using the combined support structures of the high pretension and intensive bolts and cables combines with the guard plates of the hydraulic support, and the space for the equipment retracement would be ensured. They could provide engineering references for the layout of the retracement channel under similar conditions.