Quantification of the leakages into exhaust ducts in road tunnels with concentrated exhaust systems (ASTRA2007/004_OBF)
Overview
Background & policy context:
The problem regarding leakage is relatively new. This is due to that the requirements have changed significantly in the tunnel ventilation in recent years. Previously mainly transverse ventilation systems with linear extraction and supply air were installed to maintain air quality, today it is mostly pure exhaust systems with controllable flaps for concentrated smoke extraction in case of fire. The concentrated extraction leads to relatively large and suppressing the undesirable due to its leakage.
Objectives:
The principal objective of the research work is to create a comprehensive basis for a better understanding of the leakages in smoke exhaust ducts. The primary aim of the research is:
- A creation of fundamental knowledge in the field of leakages into smoke exhaust ducts.
- Investigation of the experience with leakage requirements and approaches in Switzerland and foreign countries.
- Quantification of leakages in existing road tunnels with smoke exhaust systems (in-site measurements).
- Development of a method to extrapolate the measurement data to arbitrary tunnels.
- Recommendations regarding prevention (e.g. reduction of leakages) and intervention (e.g. increasing ventilation capacity).
Methodology:
The research project is divided into four parts:
Part 1: Development of basics
The first part is on the one hand a literature review and on the other hand a theoretical and practical approache to leaks in exhaust air ducts. The literature already available will be collected, analysed and assessed and common practice as well.
Part 2: Measuring and data collection
The second part comprises primarily the preparation and execution of the measurements in the tunnel. In terms of a comprehensive and universal evaluation of the measurement results, the number and variety of tunnels should be high. The entire measurement campaign is ideally carried out at least in 7 tunnel systems (new and renovated) as part of acceptance tests. The choice of tunnel objects is to be defined and ev. adapted during the project. The measurements will be carried out by an accredited testing.
Part 3: Evaluation & Analysis
The analysis of the measurement results is carried out simultaneously with the measurements and mainly includes the following aspects:
- Collection of data from all measurements.
- Evaluating the data according to various criteria (age, construction, ...)
- Definition and quantification factors.
- Definition of one or more dimensionless leakage indicators for easy use in the ventilation design.
- Developing a method for easy determination of the effective leakage currents.
Part 4: Documentation
All aspects of the research are documented in a final report at the end of the research.
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