Permeability enhancement performance and its control factors by auger mining of extremely thin coal seams

Abstract

In order to improve both the pressure relief in deep coal mining and the permeability of coal seams for gas drainage, the auger mining (AM) method was proposed for mining extremely thin coal seams underneath a major coal seam to enhance its permeability and improve its pressure relief for subsequent major mining. The method was applied to Chiyu Coal Mine in China as a case study. Based on the geological conditions of the mine, the influences of AM parameters such as AM width, intermediate coal pillar width and distance between adjacent temporary wide pillars on the pressure distributions and permeability enhancement were studied in detail and the optimal set of parameters for the mining operation were obtained. Based on our simulations, it was found that using the proposed method with the optimal parameters derived, the permeability of the upper protected coal layer will increase by more than 671 times the initial permeability. This demonstrated that the proposed new AM method is effective for the purposes of pressure relief and permeability enhancement in the protected major coal layer.