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Large-scale coal mining has created many goaf areas, which have become one of the most frequent sources of mine hazards. Investigations on the stress–fracture–seepage characteristics around goafs could help with identifying and controlling goaf-area hazards. Scholars have conducted theoretical analyses, similar simulation experiments, numerical simulations, and field measurements to analyze the multifield coupling development of mining stopes, including the stress variations, fracture advancement, and permeability-change characteristics. In the longwall-mining process, a stress-relief zone is formed above the goaf area, while a stress-concentration zone is formed in the adjacent coal seams. Mining-stope fracture goes through a process of stress-relief expansion, stress-recovery closure, and end-fracture expansion. The permeability of coal rock in mining stopes rises in all directions with the increase in the fracturing ratio. Further studies could concentrate on the distribution characteristics of the abutment pressure around the goaf area. A permeability model based on the coupling of the coal stress, damage, gas adsorption, and desorption is expected to be established to improve the accuracy of the permeability prediction and seepage analysis at the boundary of the goaf area. Relevant studies could provide better theoretical guidance for preventing hazards, such as gas-related incidents and coal spontaneous combustion in the goaf, as well as for the stability control of the goaf boundary.
Gong et al. (Sun,) studied this question.