Explanation of conclusions after analysis of fire tests in road tunnels

Research commissioned by Rijkswaterstaat has shown that the fire resistance of tunnels made of ROK concrete may be impaired. In response to this, four discussion tables were set
up at the end of 2017 under the coordination of the Knowledge Platform for Tunnel Safety (KPT) with the aim of discussing the problems outlined above from various perspectives.
These are the discussion tables for Existing Tunnels, New Tunnels, Research, and Emergency Services. 

This document was prepared by Discussion Table – Research in response to the request for further substantiation of the final conclusions. The explanations presented here basically reflect the way in which each conclusion was reached and the reasons for it. The conclusions (and the explanations) should, however, be considered as a whole, in view of the order in which they are reached and to safeguard the message. In this context, the broader and to some extent overarching Conclusion 6 can be seen as supporting the previous Conclusions 1-5. With these end conclusions, the Discussion Table – Research, aims to contribute to the fire resistance of (road) tunnels.

It recommends the adoption of the basic assumption that unprotected concrete in tunnels is basically to be considered susceptible to spalling. This is based on frequent observation during fire tests and is supported by the complex character of the different spalling mechanisms. Another important aspect of the fire resistance of tunnels is the awareness of the phenomenon that concrete may spall, especially in the event of a major fire. In this context, it is recommended to further investigate the susceptibility and possible consequences of concrete spalling for tunnels.