Spontaneous coal combustion was proved to cause methane accumulation and methane explosions in coal mine goafs. To avoid possible methane explosions, the empirical engineering measure, ventilation dilution, is proposed in coal mines though its disaster prevention mechanism has not been well understood. Through experimental and numerical simulations, the superposition effect of the air leakage and coal combustion-induced chimney effect was studied to reveal disaster prevention effect of ventilation dilution. Research results show that the high temperature area of coal combustion is steady and can provide continuous buoyancy force to form upward airflow even under ventilation dilution; the drifting methane accumulation is observed under the superposition effect of air leakage and upward airflow; ventilation dilution can weaken and even eliminate methane accumulation by overcoming chimney effect, but an increase in coal combustion temperature will enhance the upward airflow of chimney effect to cause methane accumulation again. The competitive relationship between the coal combustion-induced chimney effect and air leakage provides a new insight to study methane migration for the disaster formation and prevention mechanism.

煤自燃被证明会导致煤矿采空区的甲烷积累和甲烷爆炸。为避免可能发生的甲烷爆炸，煤矿提出了经验性工程措施——通风稀释，但其防灾机制尚未得到很好的理解。通过实验和数值模拟，研究了漏风与燃煤烟囱效应的叠加效应，揭示了通风稀释的防灾效果。研究结果表明，煤燃烧的高温区稳定，即使在通风稀释的情况下也能提供持续的浮力形成向上的气流；在漏气和向上气流的叠加作用下观察到漂移的甲烷积累；通风稀释可以通过克服烟囱效应减弱甚至消除甲烷的堆积，但煤燃烧温度的升高会增强烟囱效应向上的气流，再次引起甲烷堆积。燃煤烟囱效应与漏风之间的竞争关系为研究甲烷迁移的灾害形成和预防机制提供了新的见解。