ABSTRACT
The Follo Line Project is Norway’s largest infrastructure project and Scandinavia’s longest railway tunnel. Excavation is done by four Double Shield Tunnel Boring Machines (DS TBMs) all with a diameter of 9.96 m. It is the first tunnel in Norway built with a precast segment lining. Excavation in the Norwegian extreme hard rock conditions with ground water has defined the main challenges of the Project. The experience gained so far, at a progress of 83% on the TBM drives, has been extremely positive. TBM penetration, cutter wear and TBM advance rates are well within the expectations. The management of ground water has been more of a challenge than expected. To control water inflow, pre-excavation grouting has been successfully performed although compromising the TBM advance rate but with satisfying results.
