Estimates of uncertainties and risks of the construction process  are
essential information for decision-making in infrastructure projects. The construction process is affected by different types of uncertainties. We can  distinguish between the common variability of the construction process and the uncertainty on occurrence of extraordinary events, also denoted as failures of the construction process. In tunnel construction, a significant part  of the uncertainty results from the unknown geotechnical conditions. The   construction performance is further influenced by human and organizational
factors, whose effect is not known in advance. All these uncertainties
should be taken into account when modelling the uncertainty and risk of the tunnel construction. For reliable predictions, it is essential to realistically estimate the parameters of the probabilistic model. At present, such
estimates mostly rely on expert judgement. However, these can be strongly
biased and unreliable. Therefore, the expert estimates should be supported by analysis of data from previous projects. Thisthesis attempts to address these issues.