Probabilistic models for tunnel construction risk assessment

摘要

The paper introduces different probabilistic models for prediction of tunnel construction risk. First, a simple probabilistic model for the estimation of the damage due to tunnel construction failures (e.g. cave-in collapses) is proposed. It can be used in conjunction with a deterministic estimate of the construction time/costs as a support for decision-making in tunnel construction projects. The occurrence of failures is modelled as an inhomogeneous Poisson process. The model takes into account the heterogeneity of the environment along the tunnel (changing geological conditions, changing damage potential) and it includes the influence of common factors such as human and organisational aspects. The damages caused by the failures are modelled as uncertain and they are thus represented by full probability distributions in the model. Second, the decision-making under uncertainty in construction projects is discussed. The use of the concept of utility for considering the attitude of the stakeholder to risk is demonstrated. The simple probabilistic model and the decision-making concept are applied to a case study of construction of a 480-m-long tunnel. Third, stochastic models for specific problems of tunnel construction, such as impacts of excavation on surface structures or probabilistic prediction of thickness of rock overburden, are introduced. The use of the models is illustrated on an example from Blanka tunnel in Prague.