Race towards breakthrough in Oslo 06 Sep 2018

TunnelTalk reporting

Two TBMs are racing towards breakthrough in Norway. The machines are a pair of the four TBMs working on the twin tube Follo Line railway project, which are now within meters of an underground breakthrough cavern close to Oslo city center. The TBMs are racing side by side in parallel drives towards breakthrough celebrations on Tuesday of next week, 11 September, starting at 11am Norwegian time.

Which of the two hard rock TBM Queens will be the first to breakthrough? They broke through at the same time!

The machines will breakthrough into a cavern in the mountain near Oslo to end their 9km long northward drives. Two TBMs progressing southwards in the opposite direction from the mid-point working access adit will have the same length and will complete the longest rail tunnel to date in the Nordic countries.

With guests and tunnel workers ringside, the breakthrough, or twin breakthrough, next Tuesday, will be the first for the 20km long hard-rock, segmentally-lined tunnel on the new Follo Line, running from Norway’s capital to the city of Ski. The final breakthroughs for the TBMs heading southward are scheduled for Spring 2019. To this point two-thirds of the Follo Line Project is now complete.

The new double track rail line will reduce by 50% the current travel time between Oslo and Ski. It is the largest infrastructure project in Norway to date and forms an important part of the intercity rail network development by Bane NOR, the Norwegian National Railway Administration.

The two TBMs working towards Oslo are racing towards breakthrough
The two TBMs working towards Oslo are racing towards breakthrough

Bane NOR chose TBM excavation with installation of a precast concrete segmental lining for the main 20km long tunnel on the project and construction consortium JV Acciona Ghella selected four 9.96m diameter TBMs manufactured by Herrenknecht in Germany for the task. Operation of the four 9.96m diameter TBMs is managed from the one centrally located job site with each pair of TBMs progressing in opposite directions towards the tunnel portals. Excavation started in early September 2016 with launch of the two northward TBMs, which are now competing to reach their breakthrough close to Oslo‘s Central Station and ahead of schedule.

TBM excavation with installation of the gasketed watertight segmental lining as they progress provides major environmental benefits compared to drill+blast excavation from several access points. Conveyor belts transporting the excavated material from the tunnels to be reused as part of the construction foundations for a new residential area surrounding the site, results in a reduced number of vehicles and traffic movements on public roads and an associated reduction in pollution. The mechanized excavation method and its precast concrete lining offers a model for future railway projects in Norway.

Factory acceptance of the last of the four TBMs at the Herrenknecht factory in Germany

The four TBMs are working through extremely hard rock formed by several glacial periods and it is the two machines heading north towards Oslo that are heading towards their breakthroughs next week. Dubbed Queen Eufemia and Queen Ellisiv, the two machines are named after courageous women with historic links to Oslo and to the Medieval Park near the mountain hall breakthrough cavern.

Ellisiv was Queen of Norway from 1046 and was married to King Harald Hardråde. She was a Russian princess. Harald forced his nephew, King Magnus, to divide the kingdom between them, and when Magnus died shortly after, Harald became sole king of Norway and Denmark. Eufemia was Queen of Norway from 1299 and married King Håkon Magnusson in St Mary's Church in Oslo. The ruins of St Mary's can be seen today in the Medieval Park, beneath which the new Follo Line railway will run in a covered subsurvace superstructure.

The race has been on between the two hard rock TBM queens for two years since their launch in September 2016 and on Tuesday next week, the winner will be revealed when the first breakthrough is recorded.


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