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Future of Tunnelling | Norway's Rogfast Tunnel

Domcumr

Norway is using a range of tunnelling techniques to rise to the challenge of tunnelling across fjords on its west coast.

On 5 October, thousands of eager athletes will assemble at the start line for what must surely be one of the most unusual road races of all time. The 20km half marathon is due to take place east of Stavanger, Norway’s fourth largest city, through the newly completed Ryfast road tunnels beneath one of Norway’s fjords.

The runners will face a steep descent to a depth of 292m below sea level, followed by a stamina-sapping uphill slog back to ground level. Along the way the tedium of running in a concrete tunnel should be alleviated by frequent light art installations, whose ultimate function is to reduce the risk of vehicle drivers losing concentration during their long haul underground.

Similar measures will be adopted in the 27km twin bore Rogfast tunnel, currently under construction to the west of Stavanger.

The Rogfast tunnel will be a vital link in the mammoth 30 year multibillion pound E39 coastal highway project which includes numerous fjord crossings along its 1,100km length.

The E39 links Kristiansand and Trondheim on the west coast – the so-called “golden coast”– home to one third of the country’s population and generated 60% of Norway’s exports, Norway’s Public Roads Administration E39 programme manager Kjersti Kvalheim Dunham told an audience at New Civil Engineer’s recent Tunnelling Festival 2018 event.

“It’s nearly 1,100km from end to end – but the journey takes 21 hours on a good day, because of the seven ferry crossings en route. By 2035 we should have cut that to 11 hours by replacing the ferries with fixed crossings.”

Norway’s west coast route is notorious for the many fjords that cut deep into the land. Some are gigantic obstacles, up to 5km wide, and up to 1.25km deep.

“There is a total of 10 that couldn’t be crossed with the technology of the time,” said Dunham. “Now, however, new technologies are becoming available, and we can begin to look at very innovative solutions for these extreme crossings.”

Rogfast is a little more conventional, but still pushing boundaries.

Norway already has considerable experience with extreme hard rock tunnels, not least the then 24.5km Laerdal Tunnel on the E13 route linking Oslo and Bergen, which opened in 2000. The Rogfast Tunnel will be slightly longer but much deeper, setting a new world record of 392m below sea level at its deepest point.

On the Laerdal tunnel a big effort was made to minimise the mental strain on drivers faced with a 20 minute drive through many kilometres of essentially featureless tunnel. Three large caves were dug out at 6km intervals, with bright lighting and rest areas, as a palliative to claustrophobia.

No such caverns are planned for the Rogfast Tunnel. Instead, bore diameter is 10.5m, larger than strictly necessary to relieve the claustrophobia experienced by drivers.

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