Page 11 - TunnelTalk Annual Review 2015

Construction begins on
The main TBM tunnelling contract for the Oslo-Ski Follo Line railway project in Norway was awarded in March 2015 to a JV of Acciona Infraestructuras SA (Spain) and Ghella SpA (Italy). Valued at NOK 8.7 billion (about US$1.2 billion), the EPC (engineering, procurement and construction) contract comprises 19km of hard rock, segmentally lined TBM excavation and all associated works including development of a large working site at Åsland and drill+blast of large assembly caverns approximately 1km inside the mountain from where four TBMs of about 10m diameter will progress, two each in opposite directions, to complete twin parallel headings of approximately 10km each (Fig 1).
After signing its contract, Acciona/ Ghella placed an order for supply of the four 9.96m diameter shielded rock TBMs for the project with Herrenknecht AG. Manufacture of the TBMs progressed at the company’s main workshops at Schwanau, Germany and delivery to site is scheduled for summer 2016. TBM excavation is programmed to start by the end of 2016 and to continue for about two years.
Concrete segments for the TBM tunnel lining will be cast in a production factory at Åsland. Transportation of excavated material will be via continuous conveyor systems and a large transformer installation at Åsland will provide power for the TBM and construction operations from the national electricity grid.
Along with Acciona/Ghella, five other groups prequalified to submit bids for the coveted TBM contract:
• Gülermark/Samsung/Pizzarotti
(Turkey–Korea–Italy)
• Implenia/Hochtief/Dragodos
(Norway–Germany–Spain)
• NCC/Vinci/Wayss & Freytag
(Norway–France–Germany)
• OHL/SK (Spain–Korea)
• Skanska/Strabag (Norway–Austria)
Acciona and Ghella have previous cooperation experience on similar mega projects including the Legacy Way Motorway Tunnels in Brisbane, Australia where it also used Herrenknecht double shield machines of 12.4m diameter.
The JV has sourced key competence in Norway for groundwork development of the working area at Åsland and Atkins for railway engineering expertise. Through the law firm Haavind, the JV will ensure that it fully complies with Norwegian employment rules and pay conditions.
Ahead of machine delivery, work started on site in June 2015 with Norwegian subcontractor AF Gruppen AS advancing the drill+blast intermediate access adit at Åsland and of the TBM assembly and launch chamber on the axis of the main rail tunnel alignment.
The four TBMs will work through hard tonalitic-granite rock of up to 350MPa in UCS and will erect the specified precast concrete segmental lining as they progress.
“In Brisbane we used the TBMs in classic double-shield mode for the full length of each 4.3km long tube and this resulted in exceptional progress rates,” explained Giovanni Giacomin, Tunnelling Director for construction partner Ghella. “We achieved rates of up to 850m/month per machine, which was something not possible with single shield machines erecting a precast segmental lining. Nevertheless,” he added, “the overall production will be affected by associated operations including regular probe drilling and extensive pre-grouting when required.”
Two other large EPC contracts are awarded for the project. In February 2015, a NOK1.2 billion (US$156 million) EPC contract was awarded to Condotte SpA of Italy for complex drill+blast excavation of the route through the Ekeberg Hill for the approaches to the Oslo main railway station (Fig 2). The contract includes drill+blast excavation of a three-track tunnel to accommodate the inbound Østfold line and the twin tracks of the Follo Line.
Also in 2015, Spanish company Obrascón Huarte Lain (OHL) was awarded the NOK 2.5 billion (US$310 million) contract to construct 3.5km of overland railway between the southern tunnel portals and total reconstruction of Ski station. The fourth large EPC contract involves extensive redevelopment works at Oslo Central Station.
“The competition for the EPC contracts
Shani Wallis, TunnelTalk
has been extensive,” said Deputy Director General of the Norwegian National Rail Administration, Gunnar G. Løvås. Project Director Erik Smith added that, “the offers we have received and the award values are within the project budget.”
The Follo Line is scheduled for completion at the end of 2021 and forms the core part of InterCity rail development southwards from Oslo. The mega project is executed by the Norwegian National Rail Administration (NNRA) on behalf of the Norwegian Ministry of Transport and Communications. n
References
• Rapid excavation breaks through in Brisbane – TunnelTalk, April 2013
Follo Line in Norway
Global connections
Fig 1 (top). Four TBMs will progress from the central access adit at Åsland; Fig 2. Complex drill+blast approach to Oslo Station
Main picture: Åsland access adit site and (inset) junction with the TBM assembly chamber
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