Experimental research on fire smoke exhausting of super large cross-section urban tunnel

In order to investigate the fire smoke diffusion and migration characteristics of super large cross-section urban tunnel, a 1/15 scaled tunnel model was established based on Xintang interchange with covered, and experiments were carried out under the longitudinal smoke exhaust mode. The morphological characteristics of the smoke layer and the smoke temperature distribution in the tunnel under different longitudinal air velocity under the longitudinal smoke exhaust mode are obtained, the critical air velocity of the actual project is determined. Results indicated that, during the initial stage of fire in large cross-section road tunnel, the fire scale and air velocity are important factors, which affect the temperature field and smoke diffusion. The hot smoke from the fire in tunnel tends to diffuse to the vault. Therefore, the high temperature region occupied the upper space of the tunnel, while the temperature of lower part was lower. Larger inner space of large cross-section road tunnel is conductive for fire smoke spreading. The longitudinal smoke exhaust wind velocity that controls the smoke not to produce countercurrent is about 3.0 m/s. Due to the elimination of the diaphragm in the same direction, the heat generated by the fire source has an impact on the downstream of the adjacent ramp. The temperature in the downstream area of adjacent ramps increased, which is lower than 30 ℃.