Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Parallel lines

Rail - Mountains, wetlands and rising ground levels are among the challenges facing engineers building Sweden's Botnia Banan railway. Report and photographs by Adrian Greeman.

When the Swedes built a railway link to the far north a century ago, they set it tens of kilometres inland from the sea for fear of the Russians. It was thought the Tzar's navy might bombard it.

The line runs through empty northern forest land, disturbing the roaming moose but missing the 350,000 people who live in a series of Baltic coastal towns.

It also means the line follows winding contours with substantial gradients, slowing trains and limiting them to 1,000t loads.

The line also has to feed traffic to the world's biggest iron ore mine at Kiruna on the Arctic Circle, with container traffic from Finland and Russia. So traffic is heavy and congested.

The Botnia Banan line creates a new 180km long section of single track from Nyland to the university town of Umea.

It continues a 250km/h link to Stockholm recently upgraded as far north as Nyland.

The SKr13,200M (£960M) project is being developed by a special company called Botnia Banan which is 93% government owned and funded by long term bank loans. Local councils own the remaining 7%.

A dozen high speed passenger trains, a dozen regional trains and dozen 1,600t freight trains which are expected to run along the new line daily will stimulate this whole region, which is not well served by rail or road. Some 22 double tracked sections of line will allow faster trains to overtake without disrupting timetables. Gradients on these sections will be 1%, not 1.7% as they are elsewhere.

Works include seven stations and a major 7km diversion around Umea, the biggest town on the line with a 12,000 population.

The diversion will create a second route to supplement an existing but slower rail line into the town which has many level crossings.

The line has other major works along the way including a 6km and a 5.2km tunnel to the south, which are being built by Skanska.

There are also extended areas of rock cutting plus 14 other small tunnels, 140 bridges including a 2,000m crossing of the Umeõlven river, a 1,000m crossing of the +ngermanõlven and another 500m long structure. Many of the bridges are already in place.

The 2km curved white viaduct across the estuary of the river Umeõlven, has proved to be a major challenge.

It passes across spring migration stopover grounds for Arctic wildfowl, and has faced vigorous opposition from bird protection groups, which is threatening to delay the planned opening of the scheme by two or more years.

The groups have a strong hand to play on a project which is one of the first to be built under new environmental laws which created an 'environmental court' system.

A recent court ruling ordered Botnia Banan to create 50ha of compensatory wetlands to replace 15ha of European Union protected land taken by the project. This will costs another £3M delaying completion by two years until 2010. An appeal is now in progress.

Consultant WSP weden has been working on the civil, mechanical and electrical design on two 18km long sections of the line north of the port town of Írnsküldsvik.

It is one of a number of consultants on the project which is divided into relatively small sections for design and construction.

The WSP sections are 'not so dramatic' as some parts of the line says the firm's local project manager Henrik Jönsson. It has only two small tunnels 300m and 600m long.

But it has some problems.

'The area is rising fast at around 10mm a year, ' he says. The ground has to be treated or kept sealed and this has been one of the factors affecting the route alignment.

Balancing the cut and fill is another challenge. The project uses crushed rock embankment because the clay is unsuitable.

Skanska has been struggling to finish the biggest project on the line, the Namntall and the Bjürnbüles tunnels. At 6,000m and 5,200m respectively, they carry the line through the mountains behind the picturesque High Coast region.

They are the longest rail tunnels in Sweden.

The ancient Grey Wacke rock is heavily fractured, slowing progress, says project engineer Mattias Widenbrant.

Fracturing has created large intrusions of clay, sand or graphite, which can be anything from 10mm to 1m wide.

Drill and blast is being used to create a main rail tunnel 8.6m high and 8.4m wide and a parallel service and emergency tunnel 6.25m high and 5.2m wide.

Six Atlas Copco three boom rigs, three modern computerised EXL3C machines and three older ES machines have been dividing their time between a total of 16 driving faces on the project, created by side access adits.

The intrusions slow down drilling and can cause the drill rods to jam. 'And it is very difcult to properly grout these sectors to get the level of watertightness required for a rail tunnel, ' Widenbrant says.

The two tunnels are nearing completion.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.