Air leakage control at the working face end corner in shallow-buried spontaneously combustible coal seams using inflatable bag sealing

Shallow-buried, closely spaced coal seams are significantly affected during mining-induced disturbance. The mining faces in such conditions are commonly characterized by multiple air leakage pathways and interconnecting leakage channels, posing a substantial risk of spontaneous combustion of residual coal in the goaf. Air leakage sealing in the goaf is a key measure for preventing coal spontaneous combustion. Therefore, this paper investigates air leakage control technologies at the working face end corner in shallow-buried, easily spontaneously combustible coal seams. By combining surface crack morphology observations with numerical simulation methods, the study identifies the working face end as a critical zone for air leakage sealing. Based on the simulated evolution of leakage fractures, a prism-shaped inflatable sealing bag is designed. A novel method for long-distance transportation and deployment of high-water-content material-based inflatable bags is proposed for goaf sealing applications. The proposed technique is applied to the 22525 working face in the Halagou Coal Mine of Shendong. The effectiveness of the inflatable bag sealing method in controlling air leakage from the goaf is evaluated by monitoring changes in O₂ concentration and leakage volume. Experimental results demonstrate that the inflatable bag sealing effectively alleviated the low-oxygen issue at the corner of the return airway. The O₂ concentration in the return corner increases from the initial range of 14.8%-17.5% to 17.8%-20.0%. Before the sealing operation, the air leakage volume at the 22525 working face is 160.79 m³/min. After implementing the inflatable bag sealing on the return side of the goaf, the leakage volume decreases to 94.72 m³/min, indicating a reduction of 66.07 m³/min or 41.09%. The findings of this study provide technical reference for controlling air leakage at the corner of the working face and offer practical guidance for the prevention of coal spontaneous combustion.