Energy accumulation characteristics and rockburst mechanism of surrounding rock at heading face of extra-thick coal seam

Taking the extra-thick coal seam heading face in Liuhuanggou Coal Mine as the engineering background, the energy accumulation characteristics and rockburst mechanism of the surrounding rock at heading face of extra-thick coal seam are studied using field investigation, expriment of rock mechanics and theoretical analysis. The following results are obtained: (1) According to the exprimental results of rock mechanics of 9-15 coal seam and rock in Liuhuanggou Coal Mine, when the burial depth is between 100 and 1000 m, the energy density of coal and rock is proportional to the burial depth, and the energy density ratio of coal to rock is between 1.8 and 2.3. (2) Under the same depth conditions, the elastic energy accumulation of the surrounding rock at heading face of extra-thick coal seam is much larger than that of thin and medium-thick coal seam, and the structure of the surrounding rock with high elastic energy accumulation is one of the reasons that the heading face of the extra-thick coal seam is more prone to rockburst. (3) The accumulated elastic energy of the surrounding rock is proportional to the thickness of coal seam and the radius of roadway within the influence range of tunneling. Under the same radius of roadway, the greater the thickness of coal seam, the greater the accumulated elastic energy of the surrounding rock. When the radius of roadway is 3.0 m, the accumulated elastic energy of the surrounding rock is 1.4 times and 2.0 times that of the roadway radius when it is 2.5 and 2.0 m. (4) An evaluation method for impact hazard considering thickness and impact tendency of coal seam is proposed. This method is more scientific and reasonable than the current evaluation method for impact hazard, and the evaluated results are more in line with the actual situations. The research results can be used for reference in the prevention and control of rockburst at the heading face of the extra-thick coal seam.