TBM tunnelling begins on Norway’s Follo Line 22 Sep 2016

TunnelTalk reporting

Prime Minister Erna Solberg of Norway was on hand to officially name the first two TBMs of the twin-tube Follo Line railway tunnel project between national capital city Oslo and regional commuter town Ski while Minister of Transport and Communications, Ketil Solvik-Olsen, launched them on their 9km long hard rock drives towards to Oslo.

Prime Minister Erna Solberg names the TBMs
Prime Minister Erna Solberg names the TBMs

Construction JV Acciona of Spain and Ghella of Italy procured the first two of four TBMs for the 20km long twin tube project from Herrenknecht AG of Germany. All four TBMs are on site and the second two machines for the drive towards Ski from the central construction adit at Åsland are in assembly for a scheduled start on their 9km long drives before the end of this year.

The naming and launch ceremony for the first two machine on 9 September 2016 marked the beginning of the excavation of what will be Scandinavia's longest railway tunnel in a €1 billion project awarded to Acciona/Ghella by the Norwegian railway authority Jernbaneverket in March 2015. TBM excavation and concurrent installation the precast segmental lining by the double-shield hard rock machines is expected to take about two years with final breakthrough at the end of 2018.

From manufacture to launch for first TBM

The four machines will work in opposite directions from a substantial assembly, launch and staging cavern blasted out of the hard gneiss of the mountain at the end of the 1km long drill+blast Åsland adit. Segments for the permanent watertight lining of the twin tube rail tunnels are being cast in a factory located at the adit site and all excavated rock will be transported by continuous conveyor to stockpile at the adit ahead of being recycled into the segment concreting production cycle.

The naming and launch ceremony was attended by 90 guests representing the municipalities along the Follo Line route together with the Italian and Spanish ambassadors to Norway, representatives of the project owner Jernbaneverket and executives of TBM-contractor Acciona Ghella JV.

“We are very impressed with the work being done at Åsland,” said Deputy Director General of Jernbaneverket, Gunnar G. Løvås. “Thanks to a magnificent effort by the main contractor and subcontractors, the project is right on track. Start of the first TBMs to bore is a very important milestone for the project and for the Norwegian National Rail Administration.”

Junction of the Åsland access adit and the main TBM assembly chamber
Junction of the Åsland access adit and the main TBM assembly chamber

“Now is when work really begins,” said Project Manager Fernando Vara of Acciona Ghella. “We have been preparing to start TBM-tunnelling for a year and a half now, and I am proud to say we are are ahead of schedule. We have established a good working relationship with the Norwegian National Rail Administration and have created a strong international team to work with Norwegian managers and suppliers.”

Meanwhile, on another part of the NOK1.2 billion (US$156 million) project, drill+blast crews recorded the first breakthrough on the main tunnel alignment in June 2016. After almost a year, construction company Società Italiana per Condotte d'Acqua of Italy, completed excavation of the 1,600m Inbound Østfold Line tube as one of the three main tubes on the approaches of the Follo Line into Olso Central Station. Surveyor services by the Amberg Technologies team achieved a precision alignment breakthrough of 4mm lateral deviation, 1mm longitudinal deviation and 0mm height deviation.

Complex drill+blast works through Ekeberg Hill <br><br>
Complex drill+blast works through Ekeberg Hill

In the next two years another 3,500m of complex assignment drill+blast excavation will be completed under the NOK 1.2 billion (US$156 million) contract. The three tunnel tubes through Ekeberg Hill will combine the inbound Østfold line, the inbound Follo Line, and the outbound Follo Line tracks and a 1.2km reach of the twin track Follo Line into the hillside.

A third construction contract on the project is awarded to Spanish company Obrascón Huarte Lain (OHL) for the NOK 2.5 billion (US$310 million) remodelling of Ski Station and construction of 3.5km of overland track alignment.

The full project expected to be opened for service by 2021.

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