Prequalifiers confirmed for Oslo-Ski Follo Line 11 Oct 2013
Peter Kenyon and Shani Wallis, TunnelTalk
Internationals feature strongly in the nine joint venture teams and three single companies prequalified by Norwegian rail administration, Jernbanverket, for tunnel construction of the new Follo high speed rail connection between Oslo and Ski. A total of 17 companies, featuring some of the biggest construction names in Europe and Asia, are now invited to make proposals to complete the 20km twin TBM-driven and precast concrete segmentally lined tunnels for the majority of the 22km long line, and for the 2.8km of drill+blast tunnelling through the Ekeberg Hill on the approaches to Oslo Central Station.

Plan of attack for Oslo-Ski Follo Line

Prequalification is for the two excavation contracts; one for the TBM headings using four machines working in opposite directions from a single central access adit, and the other for the drill+blast works. The prequalified groups are invited to tender the contracts on a an engineering, procurement and construction (EPC) turnkey basis.
The six joint ventures for the twin TBM tunnels are:
• Acciona Infraestructuras (Spain)/Ghella (Italy)
• Gülermark (Turkey)/Samsung (Korea)/Pizzarotti (Italy)
• Implenia Norge (Norway)/Hochtief (Germany)/Dragados (Spain)
• Obrascon Hauarte Lain (Spain)/SK Engineering and Construction (Korea)
• Skanska Norge (Norway)/Strabag (Austria)
The three joint ventures and three individual companies prequalified for the drill+blast works are:
• Implenia Norge (Norway)/Hochtief (Germany)/Dragados (Spain)
• JV Skanska Norge (Norway)/ Strabag (Austria)
• Salini (Italy)/Impregilo (Italy)/Impresa Costruzioni (Switzerland)
• AF Gruppen Norge (Norway)
• Obrascon Huarte Lain (Spain)
• Società italiana per condotte d'acqua (Italy)
Complex underground connection (red) to Oslo Central Station

Complex underground connection (red) to Oslo Central Station

TBM operation favoured
The prequalification process was conducted in the English language only, and the contract will be tendered and conducted also only in English. "The response from both national and international companies for the two contracts has been most satisfactory," said Erik Smith, Project Director for the Follo Line Project. "The number of applications, as well as the quality, confirms that the selected contract strategy for the project is in line with both available capacity and competence in the market."
The decision to favour TBM excavation is taken after extensive study, geological survey and expert consideration of the technical, logistical and environmental issues associated with running 250km/hr high speed trains through a suburban area of Oslo.
The twin-tube TBM option with a precast concrete segmental lining for the majority of the new line was specified for environmental protection, safety and maintenance conditions. "When we made the decision, we had mainly safety and quality in mind but total life cycle costs were also a topic," explained Anne Kathrine Kalager, Project Manager for the Railway Authority. "The alignment passes through heavily populated areas, which attract social and environmental restrictions on blasting, construction traffic, noise, and dust.
Four TBMs will operate two in each direction from a single central access adit

Four TBMs will operate two in each direction from a single central access adit

TBM excavation and a segmental lining was specified for the majority of the line

TBM excavation and a segmental lining was specified for the majority of the line

Maintenance of groundwater levels is also a specific concern to protect the quality of potable and storage water aquifers and avoid surface subsidence. Protecting the operating tunnel from freezing winter conditions is also a major life-cycle maintenance concern." These considerations favoured the TBM option.
Design specification is for construction to be confined to a single mid-point access adit at a secluded rural site at Åsland, from where two TBMs will drive 10km northwards to a portal at Bækkelaget, and two more on southern headings to a portal at Langhus. TBMs of more than 10m diameter will be needed to create the minimum 9.1m i.d. of tunnels.
Drill+blast operations will cover approximately a third of total excavations for the project including a central working access adit up to 1,000m long, emergency cross passages between the two TBM-bored tubes, and the final 2.8km of twin running tunnels on the approach to Oslo Central Station.
TBMs will excavate the Oslo-Ski Follo Line - TunnelTalk, November 2012
Direct twin-tube route for Oslo-Ski railway - TunnelTalk, October 2010
Outreach for Norway's major rail tunnel project - TunnelTalk, March 2011
International bid for Norway rail project - TunnelTalk, December 2008

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