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Crushed coal pillars on both sides of isolated Island working face will form multiple goafs in series, resulting in complex air leakage in goafs. Therefore, it is crucial to explore the law of coal spontaneous combustion in the goaf of the isolated Island working face. Taking the W3 2 25 isolated working face of Qianyingzi Coal Mine as the engineering background, a reliable numerical model was established and different porosity ratios of adjacent goafs and coal pillars were set. Oxygen and methane concentration distributions in goaf were calculated to identify the zones with spontaneous combustion hazards. The following conclusions were drawn. Spontaneous combustion hazards exist in the multiple goafs, and the areas of the zones with spontaneous combustion hazards in the goaf of the working face account for a large proportion of total areas of spontaneous combustion hazards. When the porosities of adjacent goafs within 10 m on the coal pillar sides or the porosities of coal pillars are reduced, the risk of spontaneous combustion hazards of multiple goafs is reduced. When the porosities of both is reduced simultaneously, the risk of spontaneous combustion hazards in multiple goafs and coal pillars is greatly reduced. According to the simulation results, the porosities of adjacent goafs and coal pillars on both sides of the isolated working face can be reduced by means of shotcrete and grouting, which can reduce the series air leakage channel between each goaf, thus the fire prevention and extinguishing ability of the working face will be improved. Ultimately, the pressure on working face advancement can be relieved.

combustion science and technology

Identification of zones with coal spontaneous combustion hazards in the three goafs surrounding an isolated Island working face: A case study on Qianyingzi Coal Mine