Investigation on stress-seepage variation characteristics around coal mine goaf

To investigate stress-seepage change characteristics around goaf area, a theoretical damage-based model on gas flow was established. Distribution characteristics of stress and fractures during coal mining and damage-based gas flow properties were analyzed. Results reveal that coal mining leads to a symmetrical distribution of stress field about the middle of working face, while stress concentration occurs at both ends of goaf. As the mining working face advances, stress concentration degree at both ends increases. Meanwhile, stress-relief range above and below working face increases significantly, with a better stress-relief effect observed within 30m from goaf floor. Stress release rate is mostly above 85%. As coal mining progresses, plastic damage surrounding goaf area also expands and intensifies, resulting in formation of a plastic damage zone with a 'saddle' shape once the working face advances to 160 meters. Due to significant impact of damage, coal permeability within 10 meters from the floor of goaf increases sharply. Permeability near the floor of goaf could rise by about 830 times, leading to a substantial rising in gas emission rate in stress-relief floor layer. These results could provide effective theoretical reference for preventing and controlling gas-related incidents around goaf.