Control mechanism of strata behavior for ultra-thick coal seam mining

• 1、Department of Mining Engineering, Shanxi Institute of Technology,Yangquan 045000
• 2、School of Mines, China University of Mining and Technology, Xuzhou 221116

Abstract：In the process of multi-layer mining of ultra-thick coal seam under thick and hard roof strata, there is a problem of strong strata behavior. In this study, the stability mechanism of different roof bearing structures was examined, based on the breakage movement characteristic of roof strata and the evolution process of roof bearing structure. The change characteristic of support load and its control measures were systematically studied using theoretical analysis and numerical simulation. The results indicate that: (1) the mechanical model of roof bearing structures is established and the separation breakage movement classification system of thick and hard rock stratum is proposed; the breakage movement mechanism of thick and hard rock stratum at different mining thickness is explained, which is "stratum fractures as a whole firstly, then moves independently - thickness of bearing stratum decreases and secondary breakage - slicing thickness increasing leading to hinge weakening"; (2) the calculating method of support load is put forward under different roof bearing structures, and the load on support shows the change characteristic of "first decrease and then slowly increase under the near-stope roof bearing structure, increases suddenly and tend to stabilize under the far-stope roof bearing structure"; (3) the technical measures for controlling strong strata behavior are put forward, such as pre-splitting roof in first layer mining, reducing the top coal recovery rate and increasing the advance speed of working face at the later stage of mining, and grouting into goaf in whole mining process; upport load can be reduced by a maximum of 37.71%.

Keywords： ultra-thick coal seam roof bearing structure separation breakage support load multi-layer mining