Centrifuge Modeling of Face Excavation in Tunnels with a Deformable Lining

This study presents the results from a series of centrifuge modeling experiments performed on tunnels in sand. The goal of these experiments was to evaluate the role of tunnel face movements on both tunnel lining deformations and collapse of the overburden soil. Specifically, a half-space tunnel was modeled, in which a strain-controlled stepper motor was used to withdraw a tunnel face at a constant displacement rate during centrifugation under a target acceleration level. In these experiments, the effects of overburden height, tunnel lining stiffness, and staged construction using the New Austrian Tunneling Method (NATM) were investigated. Relatively narrow shear bands were noticed in all of the collapse tests. Moments and shear forces measured within the tunnel lining indicate that construction staging has the greatest impact on tunnel lining behaviour. The results of the experiments are suitable for investigating whether the design approaches and partial safety factors suggested in EuroCode 7 are appropriate for ultimate state analysis of tunnel faces. Further, they are useful to identify whether modifications of the safety factors for soil and shotcrete lining are needed to achieve low and consistent failure probabilities.