A new design criterion of fire ventilation for transversely ventilated tunnels

摘要

Smoke propagation is one of the key features of fire safety design in tunnels. For longitudinally ventilated tunnels, the critical velocity at which the smoke is prevented from propagating upstream of the ventilation air is a main criterion for fire safety design. However, since the transversely ventilated tunnels cannot confine smoke to one direction, it is a main interest how effectively to extract the smoke by fresh air supply and exhaust. Although the current guidelines by ASHRAE and PIARC recommend the critical ventilation rate for the transverse system, the scientific principle for the selection of these rates is difficult to find to date. Smoke stops to propagate after a certain distance because it is extracted via the ceiling space in the transversely ventilated tunnels. The smoke propagating distance is an important design parameter for transverse ventilation because the smoke under the ceiling can be dangerous for evacuating people.