Assessing risks as soon as the preliminary studies: The example of the tunnels of a new railway line in the south of France
This paper presents the principles of the risk assessment process for tunnels which was conducted as part of preliminary studies of New Line LNPCA in the south of France between Marseille and Italy. It presents the basic principles used to estimate firstly the most likely level of technical difficulty for each site and secondly the effect of related uncertainties on costs and schedule. These uncertainties lead to the identification of unexpected events and also the estimation of their likelihood and their consequence. Particularly in the preliminary studies, uncertainties come mainly from a lack of knowledge inherent in upstream phases, called epistemic uncertainties. To quantify it, statistical tools are not relevant given the lack of data. The use of expert interviews is therefore essential.