Spontaneous Combustion Hazard Zone in the Goaf and Collaborative Prevention and Control Technique under Dynamic Evolution of Coal Pillar Air Leakage

Spontaneous combustion of residual coal in goafs is one of the most severe disasters in coal mines. In China, coal spontaneous combustion (CSC) results in an annual loss of about 20 million tons of coal and the release of pollutants, such as carbon dioxide and suspended particles, severely degrading the environment and triggering frequent secondary disasters. The air leakage behavior of coal pillars, which functions as the supporting structure at the boundary of goaf areas, enhances the risk of a CSC through seepage channels formed by fracture networks. This problem is particularly prominent in the high-ground-stress environment of deep mining. Current research primarily focuses on the mechanical properties of coal pillars, such as stress–strain and reasonable dimensions, as well as sealing materials for coal pillar air leakage, yet there is still a lack of systematic study on the collaborative prevention and control of the coal pillar-goaf system. In view of the above fact, this study investigated the mechanism of coal pillar fragmentation and air leakage and further delineated the CSC hazard zone in the goaf under coal pillar air leakage conditions. The results disclosed that coal pillar air leakage is adjusted dynamically in response to mining activities. Simultaneously, coal pillar air leakage can lead to an expansion of the CSC hazard zone in the goaf and intensify the risk of residual coal ignition. Therefore, based on multifield coupled numerical simulations, a collaborative prevention and control technique combining wind pressure matching and zonal blocking was proposed here. By regulating the dynamic equilibrium between the seepage field in the coal pillar and the oxygen distribution field in the goaf, the area of the CSC hazard zone affected by coal pillar air leakage shrinks by 52.82%. This research can provide new insights into effectively preventing mine fire accidents caused by coal pillar air leakage.