Abstract:
The air leakage network of goaf groups in shallow-buried extremely close coal seams is highly complex, and the "breathing" phenomenon induced by external atmospheric pressure disturbances poses great challenges to the prevention and control of coal spontaneous combustion in goafs. At present, the internal dynamic connectivity of this leakage network is not fully understood. When there are no through-going fractures between the goaf and the surface, the relationship between atmospheric parameter variations, the "breathing" phenomenon, and air leakage intensity remains unclear. To address this issue, taking the working face 83103 of Tangshangou Coal Mine as the engineering background, surface fracture observation, energy potential measurement, and tracer techniques were comprehensively used to investigate the dynamic air leakage patterns of the goaf groups in extremely close coal seams. The driving mechanism of the "breathing" phenomenon induced by dynamic changes of atmospheric parameters under different weather conditions and its influence on air leakage intensity of the goaf groups were revealed in the absence of through-going fractures between the goaf and the surface. Coordinated prevention and control measures for goaf groups in shallow-buried extremely close coal seams were proposed. The results showed that surface fractures did not form effective connections with the goaf of the working face 83103. A three-dimensional air leakage network of "horizontal convection–vertical downward leakage" was formed among the goaf of the working face 83103 and the adjacent and overlying goaf groups. The "breathing" phenomenon was driven by the pressure difference. Surface temperature and surface atmospheric pressure were positively and negatively correlated with the pressure difference, respectively. Under sustained positive pressure difference, harmful gases from adjacent and overlying goaf groups were released in large quantities. Based on these findings, coordinated control measures focusing on pressure equalization regulation, fracture sealing, grouting reinforcement, and extraction–replacement were proposed. After treatment, the volume fraction of CO in the return air corner of the 83103 working face decreased by 48.6%, and the volume fraction of O
2 recovered to about 20%, effectively controlling the downward leakage of harmful gases.