Influence of the Coal Spontaneous Combustion Process on the Hazardous Area of Gas Explosion in the Goaf under High-Level Borehole Gas Extraction

Due to the oxidation and heating effect of coal, the gas environment in the goaf will be affected to a certain extent, which will affect the distribution of gas explosion hazardous areas in the goaf. In this study, based on the multifield evolution law and the dynamic explosion limit of multicomponent flammable gas mixtures in the process of coal spontaneous combustion in the goaf, the determination method of the coupling disaster-causing area is established, and the influence of different conditions on the evolution law of coupling disaster is obtained. The results show that explosion limits of flammable gas mixtures in the high-temperature zone of coal spontaneous combustion increase to varying degrees. There will be a certain degree of oxygen-poor circle and methane accumulation in the high-temperature area, which affects the coupling disaster process. The negative pressure of high-level borehole gas extraction determines the range and evolution direction of the coupling disaster-causing area. With the increase in the negative pressure of a high-level borehole, the risk degree of coupling disaster in the goaf increases synchronously, and the hazardous area will migrate to the deep part of the goaf. However, due to the limitation of porosity in the deep area of goaf on the transmission of gas explosion, the hazardous area of gas explosion in the goaf is mainly distributed near the air inlet and return sides of goaf. The influence of the coal spontaneous combustion process on the multifield distribution of goaf will make some areas at the center of coal spontaneous combustion lose the risk of coupling disaster.