Development of Tunnel Dismantling Machine (TDM) in an Underground Railway Project

The MTR West Island Line (WIL) project in Hong Kong involved demolishing and backfilling a 132 m section of the existing Overrun Tunnel (ORT) through complex geology beneath densely populated urban area, in order to enable subsequent excavation of the WIL Down-track (westbound) running tunnel by tunnel boring machine (TBM). To tackle the challenge while minimizing construction risks, a bespoke tunnel dismantling machine (TDM) was innovated. The TDM worked backwards from the operational railway interface inside the ORT to remove each lining segment ring under 2.8 bar compressed air pressure, sprayed shotcrete lining for temporary support, and backfilled the remaining void left underground. The crew behind the demolition chamber of TDM worked under atmospheric pressure. Part of the backfilled tunnel was then re-excavated by slurry TBM to form the re-aligned WIL Down-track running tunnel. The TDM was able to accomplish the works safely and led to the successful opening of WIL. This paper explicates the development of the world-wide unprecedented TDM and the construction process of ORT demolition.