Fire Combustion Model Test of High Altitude Highway Tunnel and Empirical Model of Maximum Temperature Rise of Vault

In order to explore the fire combustion characteristics and temperature rise law of high-altitude highway tunnels, a 1∶16 scale model test of highway tunnel fire was carried out at an altitude of 3 460 m and 500 m, the effects of altitude, pool area, fuel composition and pool length-width ratio on the heat release rate of fire source and the maximum temperature of vault are systematically analyzed. The results show that: With the increase of altitude, the heat release rate of tunnel fire decreases, and the heat release rate of high altitude tunnel fire is about 75.3% of that of low altitude tunnel fire; With the increase of the area of the oil pool, the increase of the gasoline content in the fuel, and the decrease of the length-width ratio of the oil pool, the ratio of heat release rate increases exponentially; When the pool area is 70.56 cm²,100 cm² and 139.24 cm², the corresponding heat release rates are 8.01 kW, 10.43 kW and 21.12 kW, respectively; the heat release rate of gasoline fuel is about 4 times that of diesel fuel, when the fire source area is the same, the heat release rate of square fire is 1.3 times that of rectangular fire and 1.6 times that of linear fire. Based on the experimental date, an empirical model of the maximum temperature rise below the vault of high and low altitude tunnel fire considering the heat release rate of fire source and environmental parameters is established, it is verified that the model can be safely used to predict the maximum temperature rise of tunnel fire vault.