Norway

Final double Breakthrough at the Follo Line

The final double breakthrough of the two Herrenknecht tunnel boring machines "Anna" and "Magda" (Double Shield TBM, Ø 9,900 mm) in the Norwegian Ski completed the excavation of both 20-kilometer-long tunnel tubes of the Follo Line railway. This concludes the tunnelling work on what is currently the country's largest infrastructure project. The first two Herrenknecht-TBMs "Queen Eufemia" and "Queen Ellisiv" had already reached their destination in opposite Oslo on September 11, 2018 [1].

The miners and the 350 invited guests cheered loudly when, on the afternoon of February 26, 2019, the sister machines cracked the last few centimeters of hard Norwegian rock with maximum precision after they had worked their way through it for about nine kilometers each. "Anna" and "Magda" had been chewing through extremely hard Norwegian gneiss since autumn 2016. This successful completion of the project represents an important milestone for tunnel boring machines in a country that has so far been relying primarily on conventional drill and blast tunnelling.

"If we want to stay fit for the future, we can't just say: we'll do it the way we've always done it," says Anne Kathrine Kalager, project manager for Bane NOR. "We must always keep looking for the best methods – and as it turns out, in this project TBMs have decisive advantages." With drill & blast it would have taken a total of seven construction sites in the metropolitan area, some of them difficult for trucks to access, which would have placed a great burden on traffic and residents. In contrast, the TBM solution gets by with only one central point of attack. Two 900 meter long access tunnels connect the large Åsland jobsite on the surface with two underground caverns. From there, two machines each bore south and north respectively to create the two tunnel tubes. Kalager is expecting the Follo Line to act as a signal for further projects in Norway.

Acciona Ghella Joint Venture is commissioned by the Norwegian government’s agency for railway services (Bane NOR) to construct the main part of the tunnel at the Follo Line (EPC TBM). As of late 2022, high-speed trains are to drive through the new tunnel tubes at speeds of up to 250 kilometers per hour, halving the travel time between Oslo and the municipality of Ski 22 kilometers to the south from 22 to 11 minutes. The Follo Line represents a lifeline for the future of the Norwegian capital with its population of 600,000 and the region around Ski, which anticipates population growth of 30 percent by 2025.

 

References

[1]        Double Breakthrough on the Follo Line/ Doppel-Durchbruch bei der Follo Line, tunnel 6/2018, S. 3–5


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