Abstract: When the fire occurs near the slope change point of the underwater tunnel, the tunnel structure can be simplified into a single slope V-shaped tunnel. The smoke movement of the single slope V-shaped tunnel is affected by the stack effect. In this study, FDS numerical simulation research method is used to study the equivalent longitudinal velocity and tunnel temperature field in the single slope V-shaped tunnel fire under natural ventilation and establish a prediction model. The results show that the equivalent longitudinal wind speed generated by fire is related to the tunnel slope height and heat release rate, and its value is proportional to the 1/3 power of the heat release rate and the dimensionless slope height. The maximum temperature rise of smoke under the roof of a single slope V-shaped tunnel decreases linearly with the increase of slope. The temperature distribution of smoke downstream of the entire fire shows an exponential decay, and the steeper the slope, the more obvious the temperature decay of longitudinal smoke around the fire source, and the steeper the decay curve.

Key words: single slope V-shaped tunnel； stack effect, maximum smoke temperature rise, smoke temperature distribution