Abstract: In order to study the smoke movement characteristics under the condition of metro train obstruction in rectangular tunnel, this paper uses FDS to analyze the smoke spread, temperature distribution and critical velocity change in rectangular tunnel under the two working conditions. The results show that when there is no train blockage, the distance between the fire source and the tunnel ceiling is large, the effect of space height on flame combustion is not obvious, and the plume affected by buoyancy appears; When there is train blockage, there will be linear plumes on both sides blocked by the car roof. When there is no train blockage, the maximum smoke temperature is located above the fire source, and the two sides of the fire source decrease in turn; When the train is blocked, the high temperature zone is always located on both sides of the tunnel roof, and the temperature on the left side of the tunnel roof is slightly higher than the temperature on the right side of the tunnel roof due to the arc structure. When the heat release rate is not greater than 7.5 MW, the critical wind speed is positively correlated with it; When the heat release rate is greater than 7.5 MW, the influence of the critical wind speed on the heat release rate gradually decreases; The critical wind speed will decrease with the increase of blocking ratio. Therefore, the best effect can be achieved by accurately detecting the train stop position and optimizing the ventilation and smoke exhaust mode.

Key words: rectangular tunnel, train blockage, smoke flow characteristics, numerical simulation