A monster of a tunnel boring machine (TBM) has started a project that is writing Norwegian railway history. This 150 metre-long machine will be measuring forces with hard Norwegian gneiss and granite inside Ulriken mountain in Bergen.
In September 2015, the boring head – more than 9 metres in diameter – was lifted into place using one of the biggest cranes available. Over the course of three months, no fewer than 90 packages arrived at the construction site at Arna station, where the tunnel boring machine was being assembled around the clock.
The historical tunnel boring work from Arna through Ulriken to Bergen began on 4 December2015 and will continue for 18 months until the boring head will emerge from the mountain in Bergen. The first train will operate on the new double track between Arna and Bergen in 2020.
The product which the TBM spits out is referred to as “chips”. This is what you get when 62 steel cutters, each weighing 250 kilos, is pressed against the rock with enormous force. A boring head weighing 223 tonnes is rotated by twelve powerful electric motors with a total of 5,632 horsepower. A total of 700,000 cubic metres of rock will be carried out of Ulriken on conveyor belts.
First and biggest
According to the plan, work will continue constantly without a break six out of seven days a week. One day a week will be spent replacing cutters and other worn parts. One tunnel has already been constructed through Ulriken, so geologists can study the rock close to the new tunnel so that water leaks can be prevented and difficult sections can be secured with bolts. This is the biggest tunnel boring machine used in Norway to date, and the first time a railway tunnel has been drilled using a TBM in this country. The machine being used in Bergen has been named Ulrikke after the mountain, Ulriken.
Advantages of TBMs
Using TBMs has a number of advantages compared with traditional blasting. Electrical tunnel boring means:
- that faster progress can be made, an estimated 15 metres per day on average
- an accurate excavation profile, hence not much surplus extraction of rock masses
- automation of tunnel operation and a more continuous work process
- a better work environment and safety for tunnel workers
- less impact on the surrounding rock and less need for securing
- generally a longer service life than is the case with blasted tunnels
- less noise and vibration, and hence less adverse impact on the surrounding area
Arna–Bergen double track
- Seven kilometres of new railway tunnel will be bored through Ulriken from Arna towards Bergen.
- Sixteen evacuation routes will be constructed between the new Ulriken tunnel and the existing one.
- In order to achieve a transit loop at the east end of Arna station, 764 metres of the main tunnel will be built in the traditional way, with drills and explosives. Two diagonal tunnels will also be blasted between the tunnels, each at 150 metres.
- The existing tunnel, which was completed in 1964, shortened the railway by 16 kilometres and the travelling time between Bergen and Arna by 40 minutes.
- The new Ulriken tunnel will be ready in 2020 if everything goes according to schedule.
The Ulrikke tunnel boring machine
- built by German company Herrenknecht AG in Schwanau, near the border with France
- owned and operated by contracting consortium Strabag and Skanska
- length: 155 metres, including back rig
- total weight: 1,800 tonnes
- boring head: 9.33-metre diameter, with 62 cutters
- engine output: 5,250 kW
- has equipment for bolting, injection, probing and shotcrete