Mid-tunnel underground docking of tunnel boring machines in Singapore

摘要

Due to increased depth of tunneling, the time and cost involved in constructing a deep shaft is very high. In order to minimize the number of shafts and to shorten the construction period, it may be a viable option to drive TBM (Tunnel Boring Machine) from either side (of stations/portals) so they could meet midway. The TBMs could be then docked to establish a safe working chamber for concluding construction works including the TBM dismantling, internal concrete lining etc., without the need for any intermediate TBM retrieval shaft. This paper presents a case study of such TBM mid-tunnel docking performed in Singapore and also discusses details of structural design of temporary ground support system, analysis of settlement, assessment of potential impact on structures above the docking location and excavation sequencing.