Study on reasonable advancing speed of fully-mechanized top-coal caving face in mining contugous  extra-thick coal seams in rockburst mine

In view of the rock burst problem caused by too fast advancing speed of the working face, taking the mining of W1123 fully mechanized top coal caving face in contugous  extra-thick coal seam in Kuangou Coal Mine as the background, the comprehensive analysis method of numerical simulation and theoretical analysis is adopted. By studying the mining stress and energy evolution characteristics of coal and rock under the influence of different advancing speeds, the characteristics of overlying strata movement and breaking at different advancing speeds are analyzed, and the burst risk of coal and rock mass under the influence of different advancing speeds is evaluated. The reasonable advancing speed of the working face is determined by comprehensive research. The results show that the peak stress of front abutment pressure caused by mining in the working face shows an obvious nonlinear increase trend with the increase of advancing speed, and its increase rate gradually increases. The mining stress level under solid coal is obviously higher than that under goaf, and the front abutment pressure shows an obvious double peak shape. With the increase of advancing speed, the initial breaking distance of overburden and the elastic energy accumulated in overburden obviously increase, and the strain energy density also gradually increases. The displacement of overlying strata increases sharply with the advancing speed, and the damage range is large, showing obvious discontinuous deformation characteristics. At the same time, the faster the advancing speed, the larger the influence range of overlying strata breakage, and the more severe the migration evolution. With the increase of advancing speed, the burst risk index of coal and rock in working face increases obviously, and the risk of mining under solid coal is far greater than that under goaf. The burst risk index of 100 m behind the setup room of overlying coal seam rises sharply with the increase of advancing speed, which is a high-risk area with bursts. According to the results of numerical simulation, it is considered that the relative suitable advancing speed of W1123 working face should be no more than 6.4 m/d on the premise of ensuring safe and efficient production. The research results provide scientific guidance for safe and efficient mining of rock burst prone mines in coal seams occur in close proximity.