Abstract: Aiming at the double?deck shield tunnel with branch pipe exhaust mode in the lower tunnel, a reduced size model experiment was carried out to systematically study the smoke temperature distribution under branch pipe exhaust mode, and the influence of key factors such as fire source power, smoke outlet opening scheme (number and distance of smoke outlet) and smoke exhaust volume on the fire smoke temperature distribution was discussed. The results show that the ceiling smoke temperature gradually decreases with the increase of smoke exhaust volume, and gradually increases with the increase of the distance of smoke exhaust outlets in the area away from the fire source. The ceiling smoke temperature is the lowest when the two vents closest to the fire source are opened. The temperature below the upper and lower ceiling of the fire source presents an exponential attenuation law along the longitudinal tunnel, and the relative temperature attenuation ∆T_x /∆T _max has little change under different smoke emission and fire source power. Based on the fitting analysis of the experimental data, the longitudinal attenuation prediction model of ceiling smoke temperature of upstream and downstream of the fire source is derived.

Key words: double?deck road tunnel, branch pipe exhaust smoke, scale experiment, temperature distribution