In recent years, highway tunnel fire accidents have occurred from time to time. Because of its closeness and narrow length, once a fire occurs, it is more likely to cause mass casualties. In order to explore the evacuation safety of highway tunnel and the strategy to improve its evacuation efficiency, Nanjing Fugui mountain double line highway tunnel is selected as the research object. The simulation model is established by using pyrosim, and FDS is used to carry out the numerical simulation of fire under typical working conditions (fire source power is 3MW, 15MW, 20MW and 30MW respectively). The temperature, CO concentration and visibility in the tunnel are analyzed to determine the available safe evacuation time. The required safe evacuation time is obtained through the evacuation simulation by Pathfinder, and then the judgment and evacuation strategy optimization verification are carried out according to the safe evacuation criteria. The results show that: The greater the power of the fire source, the shorter the time to reach the dangerous state, and the fire conditions of 15MW and above can not meet the safety evacuation requirements, indicating that the safety evacuation requirements are not met in case of large fire. The safe evacuation can be ensured by increasing the longitudinal wind speed, adding smoke exhaust devices and optimizing the evacuation route. The research results can provide reference for emergency evacuation of highway tunnel fire.

In order to explore the low-temperature oxidation characteristics and evolution law of oxidized coal, this paper adopted a temperature-programmed experiment system. Firstly, the low-temperature oxidation temperature-programmed experiment was carried out on the oxidized coal formed by N₂ anaerobic cooling after the coal samples were pre-oxidized to 60 ℃, 90 ℃, 120 ℃, 150 ℃, 180 ℃ and 210 ℃ respectively. At the same time, in order to further reveal the characteristics of low-temperature oxidation behavior of oxidized coal formed under different fire extinguishing conditions, the low-temperature oxidation temperature programmed test was carried out on the oxidized coal formed after fire extinguishing with three different volume fractions of N₂ when the coal sample was pre-oxidized to 120 ℃. This reveals the changes of oxygen consumption rate, production rate of signature gases (CO, CO₂) and heat release intensity of these two kinds of oxidized coals during low temperature oxidation process. The results show that the oxygen consumption rate, signature gas generation rate and heat release intensity of oxidized coal are all lower than those of raw coal. Furthermore, the spontaneous combustion characteristic parameters of coal samples pre-oxidized to 90 ℃ are closer to that of raw coal, indicating that coals pre-oxidized to critical temperature are more likely to reignite. When pre-oxidized to 120 ℃, the higher the volume fraction of N₂, the closer the spontaneous combustion characteristic parameters of this oxidized coal are to the original coal, indicating that the coal with higher volume fraction of N₂ has stronger recrudescence ability. Therefore, it is necessary to prevent the recurrence of coal when mining the coal body in the near coal seam group, the recrudescence working face and the unsealing fire area.