Study on the coupling evolution of air and temperature field in coal mine goafs based on the similarity simulation experiments

In order to prevent the occurrence of the coupling disaster between coal spontaneous combustion and gas explosion, the similarity simulation experiments for coal mine goaf were carried out with or without heat source on the scaled-down experimental platform. Results show that the O2 diffusion speed in strike direction at the air inlet side is significantly greater than that on the air return side, especially under the condition of high ventilation velocity. The higher the ventilation velocity, the greater the risk of coal spontaneous combustion. O2 consumption and thermal convection in the coal spontaneous combustion area make it difficult for O2 to migrate to the deeper goaf. Part of the O2 in air is affected by the chimney effect, rose into the spaces formed by the caving rocks and continuously mixes with the CH4 accumulated in these spaces. Meanwhile, high-temperature area tends to expand in the direction of fresh air leakage in the process of coal spontaneous combustion in the goaf. The formed explosive gases may explode during the migration of high-temperature area, resulting in disaster accidents. Therefore, the temperature change at the location where the air leakage is serious in the goaf should also be monitored in time to prevent the coal spontaneous combustion hazards.