Different kinds of flexible solid curtains are successfully used for creating fire compartments in buildings. The main goal of the proposed research is to verify if, where, how and under what conditions similar methods, technologies and/or devices could be used in road tunnels.
Important benefits arising from building compartments or obstacles for preventing fire and/or smoke propagation could be obtained, if this could reduce the risk of fire damage to human beings, tunnel equipment and structure as well as economic damages.
Tunnels are usually complex structures with a wide range of characteristics, such as: geometry, length, slope, bifurcations, escape ways, number of tunnel tubes, exploitation characteristics, traffic, ventilation, equipment. This results in different requirements and characteristics for the realisation of compartments and the devices to be used.
Several realisation variants of the methods and technologies discussed above will be investigated in the proposed project and their applicability for different tunnel types will be assessed. This will result in the determination of solutions which are feasible form the point of view of safety, technology, realisation, logistic and cost. The results will be represented as a rough cluster. The differences between existing and new tunnels will be accounted for.
The feasibility study will account for the following criteria: technology for compartment building, kinds of devices used, practical possibilities for realisation, requirements on equipment and on their operation – mainly: ventilation, safe escape of the tunnel users, accessibility for rescue and fire-fighting teams, risk of subsequent accidents (e.g. vehicle hitting the curtains), life cycle costs (realisation costs, operational costs, possible cost reductions on other equipment), criteria related to sustainable development.
It will be finally shown, whether further need for investigations is necessary and, if this is the case, in what form – for example through extended or more in-deep research efforts.
1. Reduction of damages arising from fires in road tunnels by means of compartments
- For life and health of tunnel users, rescue and firefighting teams
- Tunnel structure and equipment
- Economic and environmental damages because tunnel closure
2. Investigation of the feasibility of the realisation of compartments for smoke confinement in the tunnel, by using flexible mechanical devices while accounting for the following aspects
- Economical benefits
- Rescue scenarios and escape possibilities
- Requirements on tunnel equipment and tunnel structure
- Operational requirements
- Life cycle costs
3. Decision matrix with main fields of application and feasible variants depending on tunnel configuration
4. Propositions for subsequent development work
The research is intended to show whether a section forming with mechanical devices at Swiss road tunnels is generally or partially feasible and makes sense or not. Assessment criteria are the structural and technical possibilities, the self-rescue, unrestricted access to the fire and rescue forces as well as the overall economic benefits in relation to costs.
The methodology shall be based on a thorough analysis on the principle of continuous confinement of feasibility (Figure 3). The result is in the form of a catalog of possible use priorities identified (cluster) -if present - and underpinned with a deepened documented case study. It enables the decision whether it is worth further developments in section of road tunnels and in depth to do research. If yes, what kind of tunnels and with what constraints. There is a distinction between new buildings and existing tunnels.
In order to allow the containment of the feasibility, benefits criteria are first formulated and discussed the principle of the section Education.
Flexible devices are commonly used in buildings as a standard measure to keep the consequences of smoke and heat in the event of a fire as low as possible. Within the scope of the present research project "Reduction of the consequences of fire incidents in road tunnels by flexible devices", it was investigated to what extent such devices can be used in road tunnels, where completely different boundary conditions and requirements apply.
In a first step, available systems were analysed paying special attention to their physical mode of action. This enabled an evaluation of the devices according to their mode of action in various types of tunnels (tunnels with natural ventilation, tunnels with longitudinal ventilation, tunnels with a smoke extraction system) as well as an in-depth analysis of the devices regarding their fields of application.
For the in-depth analysis, three types of devices were considered:
• Permeable curtains for naturally ventilated tunnels
• Fully closing curtains for naturally ventilated tunnels
• Partially closing curtains for tunnels with longitudinal ventilation.
By means of CFD calculations, the smoke propagation in the event of a fire was calculated for various tunnel configurations (longitudinal inclination, tunnel profile) both with and without devices. The evaluation of the models took place based on the development of visibility (smoke density) as well as the temporal boundary conditions for self-rescue. Whether devices lead to an improvement of the situation can be determined by simply comparing the situations where devices are applied with the situations where no devices are applied.
Permeable curtains for naturally ventilated tunnels
Permeable curtains reduce the longitudinal velocity of the tunnel air in naturally ventilated tunnels. This in turn delays the smoke propagation and improves the conditions during self-rescue. In order for permeable curtains to be efficient, the following requirements have to be met:
• Tunnel has a longitudinal inclination of over 3%
• Tunnel has a length of more than 500 m
• Devices can be activated 2 minutes after the outbreak of a fire at the latest.
There are some safety concerns regarding permeable curtains, as the device covers the complete tunnel cross-section and can, therefore, be perceived as a barrier. Generally, permeable curtains