Abstract:

In order to study the characteristics of ventilation and smoke exhausting of underwater multiramp interchange tunnel and effectively exhaust the smoke, the smoke spread characteristics of different fire source locations under longitudinal ventilation condition and different longitudinal slopes are studied by CFD method and field measurement, by taking Honggu Tunnel in Nanchang for example. And then the influence of coupling factors, such as slope gradient, fire source, ramp location, etc., on smoke spread characteristics is analyzed. Main conclusions are drawn as follows. (1) The critical wind speed of smoke exhausting should be larger than 2.5 m/s at the east import ramps; and all the jet fans at the import ramps should be turned on when fire occurs, so as to avoid the phenomenon of smoke drops in bifurcation of ramps. (2) Due to the large curvature of east exit ramps and high resistance of the tunnel, the smoke control effect will be better when the critical wind speed of smoke exhausting is 3.0-3.5 m/s and adopting the ramp with smooth flow line and short smoke flow. (3) According to the different smoke spread characteristics of import and exit ramps, and the smoke exhausting time calculated from corresponding test conditions, the smoke exhausting strategy, adjusting operation mode of original design of fan, is proposed to optimize the organization of smoke exhausting flow and improve the efficiency of smoke exhausting.

Key words: Honggu Tunnel, underwater interchange tunnel, smoke spread, field measurement, tunnel smoke exhausting