Numerical Studies on Smoke Spread in Urban Underground Tunnel with Horizontal Junctions

Urban underground tunnels usually have lager traffic volumes and complex structures comparing with other kinds of tunnel. This can give higher fire risk and also make smoke control to become more difficult once the fire occurs. The effect of the fire size and intersection angle on the smoke spread and smoke mass flow distribution in underground urban tunnel with horizontal junctions are studied by the numerical simulation in this paper. The results show that the power size can affect the smoke spread heavily, but it has little effect on the smoke mass flow distributions between the downstream main tunnel and the branch tunnels. Variation of the intersection angle almost have an effect on the smoke spread in upstream main tunnel, but its effect on the smoke spread and smoke mass flow distributions in branch tunnel cannot be neglect. The results are expected to be useful for the smoke control system design in these kinds of tunnels.