Application of Reliability Methods to Tunnel Lining Design in Weak Heterogeneous Rockmasses

Abstract

Tunnel design in weak, heterogeneous materials such as flysch poses a variety of engineering challenges. The complex depositional and tectonic history of these materials leads to significant in situ variability in rockmass behaviour. Additionally, the alterations of sandstone and pelitic layers make rockmass characterization using traditional methods difficult. As a result, significant uncertainty exists in the ground response for a tunnel through such materials. Reliability-based methods can be used to better understand the impact this uncertainty has on convergence and tunnel lining performance. By assessing the impact of input uncertainty on ground response, the probability of failure can be evaluated for a given limit state. A quantitative risk approach can then be used to select the optimum design option on the basis of both safety and cost. This paper explores this issue further and presents a reliability-based, quantitative risk approach for the design of the Driskos tunnel along the Egnatia Odos highway in northern Greece.