Speed and location are vital factors in surviving a tunnel fire, or indeedany other hazardous incident. There are many factors involved in improving the chances of surviving an incident and, as surveys have shown, widely varying conditions and facilities in existing tunnels. The European Tunnel Safety Directive of 2004 placed safety requirements on all new tunnels over 500m and situated on the TENs (Trans-European Network) highways to be complied with by 2014. The same requirements must be met by upgrading existing tunnels by 2019. The moves have also shamed operators of major tunnels not on the TENs network into upgrading their safety provisions.

Another result of the major fires has been a proliferation of study groups, both national and international, working on the nature of transport tunnel fires, the best means of emergency organisation and rescue, active fire protection and the correct means of ventilation control. Opinions still vary substantially on correct approaches, particularly in ventilation and fire protection, although a consensus is being approached gradually.

Some of the important factors for survival are:
• Traffic density. Many tunnels carry much more traffic than for which they were designed. Increased density means driving closer to an incident;
• Rapid detection and location of fires and other incidents;
• Efficient communications with tunnel users and emergency services;
• Active fire suppression (and fighting) systems;
• An effective plan for controlling ventilation the direction and flow of ventilation to remove smoke, fumes and flames from as many tunnel users as possible;
• Maintenance of power supply to services required in an emergency as long as possible;
• Proximity of fire-fighting and rescue services base, with suitable equipment to rescue tunnel users;
• Clearly indicated route to escape passages or refuges, plus obvious alarm and communications stations;
• Construction of refuges and escape routes to maintain integrity as long as possible. If feasible there should be a bias towards secure escape passages away from the affected tunnel bore rather than refuges;
• Availability of ‘fresh’ air supply to emergency refuges and escape routes.

Although correct ventilation control is a vital function in aiding fire control and preserving life, this will be covered by a technical review in the December issue of T&TI, as it is a complex subject in its own right.

This article will cover some of these important topics such as fire and incident detection and location, new developments in active fire protection, clear escape and safety information, refuges and escape route construction.

Detection
Investigations into the Mont Blanc Tunnel fire found that not only were most detection systems poorly maintained, but they also had design deficiencies. These included delays in sensing fires from moving vehicles (French end), and frequent false alarms (Italian end). An obscuration meter worked but a heat detector alarm was delayed. When the French alarm was set off and the tunnel closed in nine minutes, the fire had already reached 1,000oC. It is therefore vital for detection and alarm systems to work as quickly as possible to give tunnel users a chance of escape, particularly if they are not directly aware of the fire. Most victims stayed in their vehicles and were killed within 15 minutes of the fire being detected.

These days the preference is for continuous, reliable, heat detection systems, of which there are many available, together with frequent video incident detection units. Even so, moving vehicles make a fire or smoke more difficult to detect. Securiton’s SecuriSens TSC 515 temperature sensing cable has been described before in T&TI but briefly comprises an encapsulated acquisition and bus system linking small temperature sensors at regular intervals in the sheathed ribbon cable. Evaluation logic in a data processor scanning the sensors determines when to report an alarm or a fault to a computer or fire alarm control panel.

Securiton also supplies video-based fire detection based on the digitisation and analysis of video signals from surveillance cameras. Using special algorithms the presence of smoke or fire in the image can be determined and the difference between them. This is accurate enough to link with set levels of pre-alarm or full alarms. Such a system should be used to complement and confirm other fire and smoke detection systems since there are no standards or test specifications for such systems yet says Securiton.

Active fire protection
Rather than wait for fire-fighting teams to arrive, automatic fire suppression systems offer a major advance in tackling fires in the vital early minutes. Conventional spray barriers have been tried, but it appears that water mist systems offer the greatest potential due to the greater cooling capacity of the smaller droplets and the lower water volume requirements.

The high velocity Marioff Hi-Fog system is the subject of a separate article in this issue of T&TI. Fellow UTC Fire & Security company Silvani Anticendi also supplies a patented fire extinguishing system for road tunnels in the Italian market.

The Fogtec system from Germany is widely used on railway locos and rolling stock, but has also been selected by Eurotunnel as part of the fire fighting safety upgrade. Fogtec is part of a consortium also including Rodio J (fire sprinklers), ACIS, and contractors Eiffage and SPIE.

Efectis carried out a prior fire protection analysis, and Resirep is carrying out the civils work. Since November last year the consortium has been working on the new SAFE fire fighting stations in the tunnel and carried out a full-scale test in Spain last April with fire loads of over 200MW to simulate a 40-car freight shuttle train fire. Fogtec says that the tests demonstrated the ability of the water mist to contain a fire and limit its propagation. Eurotunnel is understood to be the first railway tunnel to be equipped with a similar system. Before specification and expert group carried out a quantitative risk assessment and cost-benefit analysis, which indicated that potential savings in the fire-fighting system would exceed investment costs significantly.

Fogtec is also being installed in the New Tyne Crossing road tunnel by TT2, as well as the existing tunnel, with fire protection consulting by Halcrow. The contract was awarded to Fogtec by the main contractor Bouygues Travaux Publics UK. In the design the tunnels are spilt into 130, 25mlong sections. In the event of a fire, Fogtec in three adjacent sections will be triggered simultaneously.

Another automatic fire suppression supplier, VID fire-kill of Denmark, also carried out full-scale tests last year. Its Tunprotec systemis a low-pressure (10-bar) watermist which, in the test, is split into 20m-long sections (Figure 1) operating fromthe tunnel centre line in the crown. The diesel pool and solid class A fire tests simulated vehicle fires with heat outputs up to 100MW. In conjunction with Entreprise Bane, also of Denmark, VID Fire-Kill used the abandoned Runehammer tunnel in western Norway. This is 9mwide, 6mhigh and 1600mlong with two carriageways. The Sintef laboratory carried out the tests themselves. In addition to the cooling effects of the watermist, it was observed that the system prevented smoke backflow in tunnel air velocities down to 2m/s.

The way out
Tunnel designers cannot expect tunnel users to react to an emergency in an entirely rational way, but the best compromise must be found to encourage them to act in as calm as manner as possible to maximize the chance of survival. The situation will be particularly difficult where large crowds are involved, such as in situations like the London King’s Cross fire, or evacuations of long trains in tunnels. Several consultations such as Pöyry and Mott MacDonald have developed crowd simulation procedures to check the designs of stations and tunnel escape routes, including likely some extraction routes. Pöyry also carries out risk assessments of safety measures to evaluate their usefulness specific to projects.

Advising tunnel users—who are unlikely to be familiar with the ‘behind the scenes’ layout—of the best way out is not an easy matter in a smoky fire, especially when those people may be panicking. As the heroic security biker of the Mont Blanc Tunnel fire, Pierlucio Tinazzi, advised those he saved to stay low and close to the tunnel wall in order to maintain direction and keep below the hot smoke. However, this is generally not the best place to see normal signage and find exit routes. Therefore communications to escapes, whether over audible means or by signage, has to take this into consideration with clear instructions not only to give correct information but also to inspire confidence and calm.

Low-level direction indicators with either emergency power lighting or luminous graphics can help self-rescue in difficult circumstances. Jalite produces a range of graphic signs in different forms according to ISO 7010:2003 standard, and using photoluminescent materials to comply with the requirement for lit signs at all material times. As well as the use of the standard ‘running man through door’ symbol, plus arrows, the ISO Standard and sign range includes standard symbols for emergency door opening, and for the location of automated external defibrillators and emergency escape breathing devices as specified for marine vessels.

Jalite developed a special range for tunnels (Jalite 316 LLL) to comply with materials restrictions for low smoke, zero halogen (LSZH) generation. Included is a seamless guidance router marker within a stainless-steel angled profile with an encapsulated photoluminescent layer. The system is set for installation in two major UK tunnels.

Ideally fire and rescue teams are able to reach tunnel users in time and permanently stationed teams at or near major tunnels facilitate this. The teams will be equipped with items such as thermal imaging cameras, mask- or helmet-integrated communications systems and long-period breathing apparati. They can also bring breathing equipment and medical assistance to assist escapees, although these will require professional training.

Non-specialist tunnel staff may be able to assist with less specialised equipment such as Dräger’s Oxy K pro breathing apparatus. Although this still requires some training, it is simple in operation and is intended for use for oxygen supply where smoke, toxic gases or lack of oxygen is present. A mask protects the face and eyes against smoke and heat. Each unit lasts for 30 minutes with immediate oxygen on starting and an approximate 20-minutes-elapsed warning.

However, with a rapidly developing fire sufficiently quick response to aid rescue seems unlikely in most cases. It is therefore left to the tunnel users themselves to find their way to a safe refuge or escape route with or without external assistance.

Refuge and escape
Passive fire protection is promoted mainly to protect tunnel structures from the damaging effects of the high temperatures developed in tunnel fires, especially from freight traffic. The EU Uptun project has demonstrated that typical tunnel fire temperatures in a road tunnel can range from 480oC for a car fire to 1400oC for a large petrol tanker fire. Many test programmes have been undertaken to study tunnel fire characteristics, one result of which is the drawing up of graphs to show typical temperature development over time. Of these, the RWS curve from Netherlands test results is generally considered the most ’severe’ and now most widely used to test fire protection systems.

The main danger to life is usually from toxic smoke and fume inhalation and this can occur much sooner than any danger of structural collapse. The classic reference point has become the Mont Blanc where it was found that coordination of services and control from both ends and safety precautions were inadequate and traffic density was too high for the tunnel conditions. After the subsequent enquiry it was decided to improve safety under one managing entity, including an increase in the frequency and quality of refuge facilities although there is still no separate escape route except through ducts within the single-bore main tunnel structure.

Much depends on the location and movements of any fire. It is important that tunnel escapees can reach a non-toxic atmosphere as soon as possible. Therefore, passive fire protection will still have a role to play in the construction of temporary refuges (pending rescue). The same may be true for escape passages in case high temperatures pass through the route before escapees use them. A particular source of vulnerability is where reinforced precast concrete is used to create separate cable and ventilation ducts and/or escape passages, as these could collapse in high temperatures, preventing escapes and producing uncontrolled spread of toxic materials.

A wide range of passive protection products is available split, generally, into sprayed-on materials and prefabricated panels.

FireMaster FireBarrier 135 from Thermal Ceramics is a refractory cement material that can spray applied in a single layer, normally over steel mesh, or installed as precast sheets. It can withstand temperatures up to 1350oC for long cycle times says Thermal Ceramics. Based on comparative tests of fire protection materials in 2005 under the Uptun project, FireBarrier 135 is claimed to produce the lowest lining temperature of the six products tested. The tests were carried out in the Virgolo Tunnel, Italy, with a 30-MW simulated tanker fire.

In normal tunnel use, passive protections must again be resistant to the possible ravages of cleaning and spray from vehicles and the road surface, as well as firefighting in an emergency. FireMaster FireBarrier 135 has undergone laboratory tests at the TNO in the Netherlands to prove its resistance to high-pressure spraying. On application it can be finished with hand towelling to provide a suitable surface for painting or attaching signs, thus avoiding cladding.

FireBarrier 135 was used in the construction of the new refuges in the Mont Blanc Tunnel to comply with the duration requirements of HCM and ISO fire curves at two hours and four hours respectively. 1700sqm of surfaces were treated with FireBarrier 135 using 110t.

BASF Meyco’s Fireshield 1350 is another spray-applied insulation material to prevent heat from damaging concrete and its steel reinforcement. Meyco says it is able to withstand dynamic and collision loads in the tunnel and is compatible with all cleaning and maintenance methods. As it is a cementitious mix it can be spray applied like normal shotcrete using robotic systems for larger requirements. Tunnel applications have included protection of escape tunnels in Athens.

Protecting Gotthard from fire

As excavation of the Gotthard Base Tunnel (GBT) approaches completion, the main attention turns to remaining civils works and fitting out. An important aspect of this is fire protection for the individual and the structure.

The designers consortium for the Bodio, Faido and Sedrun sections selected BASF Meyco Fireshield 1350 as a key element in providing passive fire protection in the cut-and-cover portion of the Bodio section. This consortium is the engineering jv Gotthard Base Tunnel South comprising Lombardi Engineering, Amberg Engineering and Poyry Infra, all of Switzerland.

The targets for selection of fire protection measures were for both individual safety (safe passage availability during the event) and cost effectiveness (a quick return to usefulness after the event). Individual safety requires the tunnel bore to be structurally safe for 45 minutes and for the neighbouring bore (usually the escape refuge) to be available for 90 minutes.

A fire protection task force, set up in 2003 by AlpTransit Gotthard assessed different fire scenarios, damage and risk levels, and protective measures with recommendations. A new time-temperature curve was adopted for the GBT to better evaluate specific fire event scenarios and the effective design of the tunnel. The valid passive fire protection methods identified were the addition of polypropylene (PP) fibres t the concrete mix to avoid spalling, increased concrete cover to protect steel reinforcement, and a sacrificial insulation layer.

In the Bodio cut-and-cover portion it was decided that the individual safety criterion required a fire protection lining to the existing structural lining throughout the whole length. This was because, in the event of fire in one bore, damage to the second bore (ie the refuge) could not be discounted. It was decided that a cement-based layer provided the best solution with a long list of performance requirements specified.

A minimum thickness of 31mm of Meyco Fireshield 1350 met these requirements, but the application thickness was increased to 35m to accommodate tolerances. A high tensile bond strength between the fire protection lining and the existing lining was achieved by hydromilling the surface to a roughness depth of 5mm and employing a stainless steel reinforcement mesh layer. Stainless steel fixing bolts provided additional security against delamination. The mesh layer includes a new spacer developed by Fischer Fixing Systems and used with Fischer nail anchors. Coloured markings show the necessary minimum thickness of mortar during application over the mesh matting.

In this case Meyco Fireshield 1350 was applied as a spray using a concrete spraying robot, covering a total area of 13 500m2.

In the application of Fireshield the work was for a pilot application to the portals of escape tunnels from the newly constructed Elefsina-Athens and Agii Theodori-Korintos rail tunnels for the Greek railways organisation OSE. Here the portal included both concrete columns and beams with brick masonry. As these have different coefficients of expansion BASF Meyco proposed a polypropylene mesh over the surfaces. Meyco TCC 735 concrete improving admixture and SA 160 accelerator were also used to ensure appropriate setting and adhesion to the substrate.

Ventilation control may not be the only way of keeping smoke away from tunnel users. About two years ago Beijing Yingtelai Morgan Thermal Ceramics Textiles (YMTT) completed the supply and installation of smokeproof curtains for lines 5 and 10 of the Beijing Metro in time for the Olympics. The curtains have also been specified for subsequent metro lines in Beijing. The curtains can be handled in three modes for easy operation. The curtains, which were invented in 2000 by YMTT, have also been exported to Europe, Japan, Singapore, Taiwan and the US.

Promat (Etex Group) fire-resistant panels have been installed in many tunnels since the Dartford Tunnel in 1963 and the Elbetunnel in 1975. Latest applications include the Schidetunnel (Limburg) and Theatertunnel (Frankfurt-am-Main), also German road tunnels.

A speciality of Dräger is the design and construction of fully-equipped refuge chambers, such as in ISO standard containers. Designed primarily for construction and mining works, they could also be used for more permanent installations, serving either as an intermediate rest station or to house escapees until rescued. The chamber is activated by an alarm and can operate for up to eight hours or 48 hours, depending on the designed function.

For more mobile needs Dräger also designs rescue trains equipped according to customer requirements. The trains carry containers for the fire and rescue crew, fire fighting equipment and evacuees. The containers can be hermetically sealed off from the contaminated atmosphere with air supplied from reservoirs and recycled. Crew and escapees can spend hours in the containers without masks. Smoke contamination during transfers is minimised by positive pressure ventilation, air locks, smoke extractors and a multistage smoke retention system. Even if the outside is masked by dark smoke, supervisors can use monitoring devices, communications and thermal imaging cameras to check on conditions outside. The equipment can also include quickfilling systems for professional respiratory equipment, thus maximising operational time and cutting the need for frequent returns to the ‘surface’. Customers for such technology include the Austrian Federal Rail Company (ÖBB), the Swiss rail companies SBB, BLS and RhB and the Deutsche Bahn (DB).


Photo of Piqueras Tunnel from the FIA (Federation Internationale de l’Automobile), which is concerned about slow progress by some countries in meeting EU Tunnel Safety Directive deadlines A test fire in a road tunnel. Note smoke layering [Photo: HBI Haerter] Smoke emerging from the Veliki Glozac Tunnel in Croatia during testing of Lios Technlogy’s fibre-optic linear heat detection system Figure 1 – Diagram of VID fire-kill from Denmark Mesh is fixed to the main lining with ‘pig tail’ anchors before applying Applying Thermal Ceramics FireBarrier 135 through steel mesh A portable refuge station for respite from escaping the tunnel from Drager. Similar refuges could be built into a tunnel Drager fire and rescue trains can be equipped according to customer wishes