Study on the critical velocity for smoke control in a subway tunnel cross-passage

The critical velocity of subway tunnel cross-passage was investigated since the smoke control mode is different from that of road tunnel and larger blockage effect of train need to be given priority. In order to ensure an effective smoke control and safe evacuation, numerical simulation and experimental study were conducted to investigate the critical velocity of subway cross-passage. On the basis of exiting critical Froude model, the influence of tunnel shape, fire location and train blocking on critical condition were analyzed. The results indicate that the blockage of train has a great influence on the critical velocity. With the shorter distance between train and cross-passage, the ventilation velocity through cross-passage dramatically increases. In addition, critical velocity with rectangular tunnel is obvious larger than that with shield tunnel. As the fire source location is closer to the cross-passage, the critical velocity would be greater and the corresponding Froude number would become smaller.