Post-fire performance of tunnel support systems has become a significant issue since the fire in the Channel Tunnel (1996) and the fatal fires in Mt Blanc (1999), Mt Gothard (2001) and Tauern (1999). There are three main issues: 1. Safety of persons in the tunnel, particularly fire and rescue personnel during and immediately following the fire, where concrete or shotcrete linings have spalled or weakened; 2. Risk of complete collapse of a length of tunnel due to weakening of concrete and rockbolt support and 3. Delays and costs associated with re-instating the support. Much testing has been done on concrete and shotcrete under design fire conditions which reach temperatures of over 1000 deg C (see Figure 1). Studies have included the use of plastic fibres in shotcrete and concrete to alleviate the problem of explosive spalling that is substantially due to the build up of gas pressures in the heated materials. Alternative passive protection systems, sprayed or preformed boards, are now incorporated in some new tunnels.
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