Quantification of the Leakages into Exhaust Ducts in Road Tunnels with Concentrated Exhaust Systems

Published:  19 April, 2010

In recent years many countries have changed their requirements for ventilating road tunnels in an emergency. Traditional linear exhaust systems are no longer permitted; the smoke has to be exhausted from the tunnel close to the fire. The design of this new ventilation system requires different treatment in many ways.

One aspect is the leakage flow into the exhaust duct away from the exhaust point. The leakage generated by the under-pressure in the exhaust duct causes a leakage flow through the closed dampers and through the structure (drainage, cabling between road level and exhaust duct, doors and manholes, joint and cracks in the concrete structure). This additional flow can have a significant impact on the efficiency of the ventilation system and therefore must be considered in the design (e.g. [1]). The main difficulty today is to quantify the expected leakage flow into the exhaust duct because very few established bases are available.

In 2007 the Swiss Federal Road Authority ASTRA initiated a research project to extensively investigate leakages into exhaust ducts in road tunnels. The principal objective of the research work is to create a comprehensive basis for a better understanding of the leakages into smoke exhaust ducts. The research work has been articulated in five phases: 1) Literature search, 2) Leakage measurements, 3) Data Analysis, 4) Development of a method to extrapolate the measurement data to arbitrary tunnels and 5) Recommendations regarding prevention (e.g. reduction of leakages) and intervention (e.g. increasing ventilation capacity).

The project is well advanced and should by completed by mid-2010. This short paper focuses on phases 2
and 3.

  • Operation Florian

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