Recent fire disasters in European road tunnels have shown that fires in a tunnel represent high risks. The users and the rescue services are endangered by heat, smoke and also explosive concrete spalling of the tunnel lining. The tunnel itself is often damaged considerably. The necessary long refurbishment works have negative effects on the tunnel service availability and also cause high costs for the tunnel owner. Thus high safety demands must be placed on complex infrastructural facilities such as road tunnels. Preventive measures designed to avoid hazards caused by fire are constantly becoming more and more important. In addition, structural fire protection is as well a point of increasing interest. In the event of fire the temperature in a tunnel rises extremely rapidly within a short amount of time. Large scale fire tests have shown that maximum temperatures of 1200°C or even above could occur. The result is an increased risk of explosive concrete spalling of the tunnel lining. Depending on depth and quantity of these spallings, the structure could be damaged seriously and in the worst case the tunnel stability could be influenced negatively. Different possible structural measures to protect the concrete tunnel lining in order to reduce or avoid damages in cases of fire are explained and discussed. A fire-proof concrete is one relatively new and promising measure to avoid explosive concrete spalling of the tunnel lining during a fire. The fire resistance of concrete can be improved by adding polypropylene fibres as well as through the application of selected concrete mixtures and aggregates. Within the scope of a research project of the Federal Highway Research Institute of Germany (BASt), fire protecting systems and especially fireproof concrete, as well as their fire behaviour and application possibilities in road tunnels are examined. (Author/publisher)
Samenvatting