A study of the second hole sealing method to improve gas drainage in coal seams

Gas concentrations drop, and the effective gas drainage period of holes is shortened, because pores and cracks in the coal seam become completely developed after gas drainage. The'second hole' sealing method is proposed as a solution to this problem. The principles are described and a mathematical model is formulated to describe the movement of fine expansion particles within the pores and cracks of the coal seam. An industrial scale test of this method was carried out over a period of six months at the Sihe mine of the Jincheng Mine Industry Group. The gas drainage concentration was improved by 25 to 50% after application of the method and the period of effective gas drainage was extended for three months.