Tunnel safety

SP Fire Technology is one of the leading institute on fire safety and research on tunnel fires. SP has performed tests and done research in the area of tunnel safety since 1992. Many papers and reports have been published on the subject. List of publications.

In 1994 SP held a conference in Borås entitled : International Conference on Fires in Tunnels, which was a great success with many participants from all over the world. From then until today the work has continued. In 2003 SP again hosted an international tunnel conference: The International Symposium on Catastrophic Tunnel Fires (20-21 November 2003). The proceedings  from this conference can be ordered.

In 1991-92 SP was involved in a European project named EUREKA. As a part of the project fire tests in a tunnel in Norway with a large truck loaded with furniture were performed. The EUREKA project was completed during 1995 and the results were compiled. Each one of the participating countries had separate tasks in the project. SP’s part was to measure and calculate the heat release rate (HRR). The results from the EUREKA project can be used for guidance when designing tunnel safety measures.

Here are some of the results from the EUREKA project:

• cold tunnel walls pull down the smoke from the ceiling and the evacuation of people becomes more difficult
• smoke from the fire is drawn back into the fire zone and the tunnel segment can become smoke filled very rapidly
• vehicles can reach flashover in minutes
• the construction of the vehicles has a large impact on the fire growth, steel structures are better than aluminium and plastic

For more details on the results see some of the references in the List of publications.

During the years several different series of fire experiments have been performed, both in real tunnels and in model tunnels. The results from some of these test series are described in the references in the List of publications. Some are still to be reported. The main conclusions from these test series are:

• The smoke spread and smoke concentration, both along the tunnel and over the cross section, is highly dependent on the type of exhaust ventilation and the longitudinal velocity.
• The thermal exhaust ventilation does not prevent smoke spread downstream the exhaust opening in any case whereas the mechanical ventilation does. The efficiency of the thermal shaft is highly dependent on the height of the shaft and the temperature inside the shaft.
• The critical flow rate of the mechanical ventilation, which prevents any smoke spread downstream the exhaust opening, is highly dependent on the longitudinal velocity.
• Fire spread is governed by the longitudinal ventilation, ceiling height and the heat release rate generated
• The fire spreads between vehicles due to heat fluxes from flames crawling along the ceiling
• The influence of the ventilation on the heat release rate is not as pronounce as have been indicated in earlier studies.
• Suppression system prevent fire to spread between vehicles

Fire test in a model scale tunnel simulating a fire in two HGVs.

In 2003 SP was responsible for large-scale fire tests performed in the Runehamar tunnel in Norway. These tests were the largest ever performed in a tunnel where the heat release rate was measured. The aim of the tests was to study the fire development, maximum heat release rate, temperature distribution, flame lengths and fire spread, radiation, and gas concentration in connection with fires in heavy goods vehicles (HGVs) trailer with ordinary cargos (‘non-hazardous’). The fuel loads consisted of mixtures of cellulose and plastics. The main results were that the gas temperatures and maximum heat release rates from this kind of fires with ordinary goods are much higher than suggested by existing guidelines and can be comparable to what is expected to be related to fires in hazardous goods. Details on the results are given in several of the references in the List of publications and the results are discussed and compared to results from other research project in a recently published doctoral thesis. Background and some details on the performance of the tests can be found here.

In SPs fire laboratory the effect of a fire on concrete and tunnel linings are investigated. A special attention is given to the modern high performance and self-compacting concrete and how these product perform when exposed to fire. The phenomenon spalling is of special interest.

European activities 

SP has taken an active part in several research projects funded by the European Commission:

• EUREKA EU 499: FIRETUN - Fires in Transport Tunnels. Nine European countries took part in the project. Over 20 large-scale fire tests were carried out, mainly in a 2.3 km abandoned mining tunnel in the north of Norway. The tests were prepared and performed in 1990-1992. The fire loads consisted of trains, trucks, cars, wood cribs and heptane fires. There is an official final report from the project, but many of the results are also presented in the proceedings from the International Conference on Fires in Tunnels held in Borås 1994.
• FIT  is a European Thematic Network on Fire in Tunnels. FIT provides a European platform for dissemination and information of up-to-date knowledge and research on Fire & Tunnels. FIT represents 33 members from 12 European Countries.
• UPTUN - Cost-effective, Sustainable and Innovative Upgrading Methods for Fire Safety in Existing Tunnels . The project was initiated in 2002 and will be finished in 2006. The project is performed by 41 partners from 17 countries. The partners constitute of tunnel owners and controllers, manufactures and suppliers, research institutes, universities, and design engineers and consultants. The main objective of the UPTUN project is to develop innovative technologies where appropriate and, where relevant, comparing to and the assessment of existing technologies for tunnel application. Focus is on technologies in the areas of detection and monitoring, mitigating measures, influencing human response, and protection against structural damage. Furthermore it is to develop, demonstrate and promote procedures for rational safety level evaluation (including decision support models) and  knowledge transfer.
• L-SURF - Design Study for a Large Scale Underground Research Facility on Safety and Security . L-SURF is a joint initiative by some of Europe’s leading institutions on safety and security of underground spaces. In due time, L-SURF will bundle the strengths of the initiating partners (from six different countries), providing a full range of services, which besides full scale testing includes training and education and also act as integrating nucleus for pan European activities on safety and security in underground spaces. The project was started in March 2005 and will end in 2008. The work within the project include: making a survey of existing facilities, identifying research needs, outline the lay-out and geometry of a future research facility, defining measurement techniques suitable to use in the facility, defining activities (e.g. R&D, training and education) that can be part of the future legal entity, and develop a business plan for the legal entity.