Analysis of Leakage Paths Induced by Longitudinal Differential Settlement of the Shield-driven Tunneling

It is a clear simplification to consider the tunnel lining as uniformly permeable. In reality, it is more likely that there are specific leaks, associated with segmental lining joints. In the case of the in situ concrete linings, construction joints can provide leakage paths, especially accounting for most of the water leakage. For transportation tunnels in saturated soils below water table, different settlements will lead to ring offsets and changes in joint opening near the edges where the gaskets are located and may significantly affect the sealant potential of the lining. In this paper, taking the metro line No.1 in Shanghai as an example, the development of joint opening and ring offset was set up based on the mechanical model of segment joint. Based on the magnitude of the joint opening or ring offset, the occurring of water leaking into the tunnel through the joint system can be judged. This analysis not only helps us realize the leakage paths of the segmental linings, but also provides the guidance for waterproof design and protection measures of the shield tunnel.