Classification of safety zones for T-shaped roadway fire in deep coal mines

The flow and diffusion of high-temperature smoke in mine fires is an important cause of safety accidents. In response to the unclear relationship between fire hazard zones and time in typical mine roadways, a safety zone classification method for T-shaped roadway fire in deep coal mines is proposed. A three-dimensional numerical model is established using Pyrosim software to simulate the high-temperature smoke flow in the T-shaped roadway during the fire development stage under high temperature and humidity conditions. The variation law of temperature field and CO, CO₂ concentration field with time and spatial location in the T-shaped roadway during the fire development stage are revealed. Based on the simulated data of the height of the human mouth and nose (i.e. the height of 1.6 meters in the roadway), the relationship between the horizontal length of the roadway and temperature, CO concentration and CO₂ concentration is obtained. The airflow mixes high-temperature smoke through the roadway and spreads downwards along the top of the roadway. As the distance from the fire source increases, the temprature gradually decreases, and the longitudinal distribution of CO and CO₂ concentration contour lines becomes denser. On this basis, safety zones are classified based on the temperature of the smoke and the harm degree of CO and CO₂ concentration to human health. The smoke diffusion area is divided into four categories: safety zone (hazard level 1), mild hazard zone (hazard level 2), moderate hazard zone (hazard level 3), and severe hazard zone (hazard level 4). The analysis results show that in the temperature classification results, the measurement points in roadwayⅠare mainly concentrated in the severe hazard zone. In the toxic gas classification results, the safety zone range of CO₂ in roadway Ⅰ is larger than that of CO. The risk factors for CO are greater, mainly concentrated in mild and moderate hazard zones. In roadway Ⅱ, it is mainly concentrated in mild hazard zones. The range of hazard level 1 in roadway Ⅰ gradually decreases over time, while the range of hazard level 4 gradually increases over time, with the maximum change rate occurring at 40 seconds. The rates of change for hazard levels 2 and 3 are very small. The regional range changes of the two classification methods in roadway Ⅱ are similar, with the maximum change rate of hazard levels 2 and 3 occurring at 60 seconds.