ABSTRACT
This study deals with a possible methodology for the choice of shield excavation method, based on an economic model. By using a geological/constructability model the robustness of the method can be defined. The robustness of the method can be increased by certain measures. A developed probability-based decision model has been used to estimate expected costs for various shield methods of excavating. Clearly formulated decision criteria are defined: the choice of method should not be based on the lowest standard cost but on the lowest expected total cost. A simulation has been carried out in a case study with three different excavation methods in the Grauholz tunnel in Switzerland. The result shows that the method can be made more robust by implementing additional measures which give less probability of major cost increases.
