Numerical Study on the Influence of Altitude on Roof Temperature in Mine Fires

The temperature distribution of the roadway roof in a mine fire is closely related to the internal environment of the mine, which changes by the mine's altitude. In order to accurately reveal the distribution of roof temperature in mine fires at different elevations, altitude should be considered as avariable. Using FDS (Fire Dynamic Simulator), six fire sources of different scales are designed to simulate fire scenarios at five different altitudes from 0 to 4,000 m (equal diversion point). The roof temperature distribution along the longitudinal centerline of the tunnel is obtained. At the same time, the influence of high temperature on the roof support of the roadway is analyzed when the mine's altitude changes. The results show that when the fire heat release rate is relatively small, the combustion belongs to fuel-controlled combustion, and the roof temperature rises with altitude. As the heat release rate continues to increase, the roof temperature decreases with increasing altitude, which is mainly due to the low-oxygen environment in plateau areas. In addition, mine fires at normal altitudes (altitude < 3,000 m) are less affected by altitude changes, and the roof temperature is always positively related to fire heat release rate. However, high altitude has an inhibitory effect on fire. In the initial stage of continuously expanding the heat release rate, There is still a positive correlation between the roof temperature and the heat release rate. When the heat release rate increases to 100 MW, the roof temperature distribution does not continue to increase. Instead, it remains stable, and the higher the altitude, the lower the stable value. Finally, based on the combination of dimensional analysis and dimensionless analysis, a correlation for predicting the longitudinal distribution of roof temperature in mine fires at different altitudes is established. The predicted data of this empirical model is highly consistent with the measured data.