TBM excavation for critical Norway rail link 13 May 2014
Peter Kenyon, TunnelTalk
The 50-50 joint venture partnership of Strabag and Skanska is awarded a NOK1.3 billion (US$220 million) contract by the Norwegian rail authority, Jernbanekervet, to construct a parallel bore to the existing Ulriken tunnel. Following technical negotiations, TBM excavation is selected for excavation of a rail tunnel in Norway for the first time in 25 years.
Bergen-Arna 7.8km parallel tunnel alignment

Bergen-Arna 7.8km parallel tunnel alignment

The new 7.8km-long tunnel will more than double capacity on the single-track Arna-Bergen section of the Bergen Line that links Norway’s second city, on the west coast, and its capital Oslo to the east.
A spokesman for Jernbanekervet said a total of 11 bids had been received, featuring a mix of proposals to complete the work using both TBM and conventional drill+blast methodology. He added that a number of the bidders had submitted proposals for using either method.
The contract was advertised on the basis of both construction methods, with bidders invited to make proposals using conventional means, TBM, or both. The winning bid came in just NOK53,000 ($8,000) less than originally estimated.
Skanska/Strabag is awarded the contract following technical discussions with the rail authority during which its proposal to use a TBM for the majority of the excavation was accepted as the best, and fastest, way to tackle the challenging alignment. Jernbaneverket’s design consultant on the project is Norconsult.

Bergen tunnel (east) portal

Arna Station (west) redevelopment

Excavation will begin from the Arna (eastern) end of the alignment using a 9.3m diameter hard rock TBM. The 6.8km drive is scheduled to take 18 months to complete. A 1km-long section from the Bergen side will be excavated using drill+blast. Skanska said in a statement that drill+blast offered the least construction risk for this challenging short section of alignment bearing in mind the mixed geology likely to be encountered at the tunnel face.
“This is the largest TBM that has hitherto been applied to a transport tunnel in Norway, and marks a new era in railway construction in this country,” said Jerbanekervet Deputy Director General Gunnar Lovas. “One must go back to the 1980s to find previous examples of rail tunneling with TBMs in Norway – and coincidentally two of these were in Bergen,” he added.
Arna Station to be substantially rebuilt

Arna Station to be substantially rebuilt

Full project scope comprises:
  • 6.8km of 9.3m o.d. TBM excavation
  • 1km drill+blast excavation
  • 15 cross passages between the new and existing bores
  • Upgrade of the existing Ulriken tunnel, including improved fire safety measures
  • Almost total reconstruction of Arna Station, plus new pedestrian tunnel under the tracks
  • Installation of 1.3km of track and associated bridges and infrastructure between Bergen station and the western tunnel portal at Fløen
The original Ulriken Tunnel was completed in 1964, but it has become a significant bottleneck on the line as a result of heavy competing demand from local commuter services to Arna, long distance passenger trains, and the freight sectors. Bergen is one of Norway’s biggest container ports (53 million tonne of freight in 2012), and its airport is the second busiest in the country (6 million passengers/year). Currently up to 120 passenger trains/day use the tunnel, plus a further 14 freight trains – which represents full capacity.
Although TBMs have been absent from Norwegian tunnelling for many years, it was recently announced that 20km of the 23km of tunnels required for the Oslo-Ski high speed Follo Line will be excavated using four machines of 10m+ diameter. That project, however, is some months behind the Ulriken Tunnel Project in Bergen. The only TBM currently in the ground in Norway is a refurbished Robbins machine that is excavating 12km of headrace tunnel for the upgrade of Røssåga hydropower station in the Arctic Circle.
References
Prequalifers confirmed for Oslo-Ski Foll LineTunnelTalk, October 2013
Hydro brings TBMs back to Norway TunnelTalk, September 2013

           

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