THE DYNAMIC INTERACTION OF TWIN TUNNELS EMBEDDED IN A HOMOGENEOUS HALF-SPACE

Abstract

Vibration generated by underground railways can be a major source of disturbance to occupants of nearby buildings. The numerical prediction of ground-borne vibration is a complicated problem that has received extensive research attention in the past decades. However, simplifying assumptions are always required in state-of-the-art numerical models in order to reduce computational effort and resources. A common simplifying assumption is to neglect the presence of a neighbouring tunnel, despite the fact that many underground railway lines around the world consist of two tunnels. This paper investigates the dynamic interaction of two parallel tunnels embedded in a homogeneous half-space. Two different methods are used to tackle the problem. The first is a fully coupled approach, where two cavities are generated in the halfspace to which the tunnels are coupled. The second adopts a superposition approach, where two sub-models each consisting of a single tunnel are superposed to calculate the vibration response of the twin tunnels. In both modelling approaches, the tunnel wall is modelled using the thick-shell theory, while the boundary element method is used to simulate the half-space of the ground. The vibration response of the twin-tunnel system on the ground surface due to a harmonic point load at one tunnel invert is studied and compared to that of a single tunnel. The efficacy of the superposition method in modelling the dynamic interaction of the twin tunnels is assessed against the fully coupled approach at different points on the surface. The results reveal the significance of the interaction between the twin tunnels and also demonstrate the accuracy of the superposition method. The feasibility of the superposition method in modelling the dynamic interaction between tunnels and piled-foundations is also highlighted.