Study on the seepage diffusion characteristics and sealing mechanism of water-based foam in loose media

Goaf air leakage is the primary cause of spontaneous combustion in loose residual coal, which not only poses serious threats to the safe production of coal resources but also contributes to environmental pollution. Sealing air leakage in goafs is a critical measure in the prevention of coal spontaneous combustion. Owing to the excellent diffusion capability of aqueous foam, dynamic foam injection into goafs can be employed to seal leakage channels in real time, thereby mitigating spontaneous combustion in loose residual coal. This study investigates the seepage, diffusion, and sealing mechanisms of foam in loose media through liquid drainage and injection diffusion experiments. Results show that foam decay is primarily influenced by liquid film interaction, medium support, and gravitational effects. The medium's support mitigates gravity-induced decay, while uniform liquid film and bubble distribution enhance foam stability. Foam seepage and diffusion in loose media create a more uniform system, improving sealing effectiveness. The foam half-life can reach 43 min, more than twice that in an atmospheric environment. The foam injection sealing process in loose media can be divided into three stages: foam injection stage, stable seepage stage, and low-seepage stage. Furthermore, the seepage diffusion and sealing mechanisms of foam in loose media were discussed, along with the engineering application of foam for goaf air leakage sealing and coal spontaneous combustion prevention during mine stoppages. The findings of this study provide new insights and a theoretical foundation for applying foam in the prevention of spontaneous combustion in loose residual coal within goafs.