Mechanism of asymmetric coal bursts on the working face in steeply inclined and extra-thick coal seam

In view of coal bursts that occur on the horizontal section of top-coal caving mining working face in the steeply inclined and extra-thick coal seam, based on the engineering background of Yaojie No. 3 Coal Mine, the evolution of roof fractures and structures during horizontal section mining in the steeply inclined and extra-thick coal seam is studied using UDEC numerical simulation. The asymmetric coal burst on the working face under the action of mining-induced seismicity is reproduced. The characteristics of asymmetric stress distribution in the bottom coal are theoretically analyzed. The mechanism of asymmetric coal bursts is proposed based on the superposition principle of dynamic and static loads. Finally, prevention measures are proposed. The results show that under the action of asymmetric peak-staggered mining-induced stresses of the working face in the steeply inclined and extra-thick coal seam, the stress in coal shows regional differences along the inclination—compression on the roof side, shear on the middle, and tension-shear on the floor side. A spoon-shaped pressure relief area in shallow and an asymmetric stress concentration area in deep are formed in the bottom coal. And the peak value of vertical stress and shear stress of the coal on the roof side is 5 times that of the floor side. As the mining depth increases, the length of the hard roof increases, and the possibility of rotation, slipping, and the toppling of the key rock blocks in goaf also increase, leading to an increase in mining-induced seismicity. When the superposition of the static stress and the dynamic stress is greater than the ultimate stress of the coal body+hydraulic support system, asymmetric coal bursts occur on the horizontal section top-coal caving mining working face in the steeply inclined extra-thick coal seam. The research results are consistent with the field measurements. © 2023 China University of Mining and Technology. All rights reserved.