A 6.2m diameter Robbins TBM broke through recently on the 7.3km long New Wuchieh tunnel in Taiwan. Contractor Kumagi Gumi battled earthquakes and typhoons to complete the tunnel, which forms part of a water transfer scheme.
The project is in an area of Taiwan subject to extensive seismic activity. A devastating earthquake hit the nearby city of Puli just a few years ago, and small earthquakes were frequent during the course of the project. Fortunately, the tunnelling works remained unaffected.
A typhoon hit the area on 30 July 2001, flooding the site with water, mud and rocks. The inter-modal shipping containers, housing, job-site spare parts, cutters and shops were completely submerged. However, the flood level stayed below tunnel level and the tunnel works were not damaged.
Geology along the alignment was primarily quartzite, sandstone and slate. The TBM had many days with production in excess of 30m, and the average monthly production was just over 400m. A best month of 650m was obtained early in the project before difficult ground was encountered and the client specified extreme rock support measures.
Ring beams, mesh and thick shotcrete were applied for much of the tunnel length. In places, cast iron segments were erected for support.
The Robbins Company supplied the TBM, the backup and ground support equipment. The TBM had variable frequency controlled cutterhead speed, and 1890kW of cutterhead power. Robbins 432mm wedge lock cutters were used for excavation.
