News, Road Technology

Through the Mountains and Over the Fjords

Much of Norway is covered by mountains and the western coast is gouged by deep fjords and dotted with islands. To facilitate modern communications it has been necessary to build roads through the mountains and over – or even under...

Much of Norway is covered by mountains and the western coast is gouged by deep fjords and dotted with islands. To facilitate modern communications it has been necessary to build roads through the mountains and over – or even under – the water. Tunnels and bridges can radically reduce transit times between cities and improve traffic safety. After all, a road passing through a mountain is safer than one winding over it, especially in variable weather conditions.

It is not surprising, then, that Norwegian companies are paving the way when it comes to hard rock tunnel construction, offering technology and planning tools that make tunnelling a viable, cost-effective alternative to building above ground in difficult terrain and urban centres alike. Norway has a total of some 600 km road tunnels, 55 of which are sub-sea. One-fourth of the world’s 100 longest tunnels are found in Norway, as is the world’s deepest (-267 m) subsea road tunnel. At 24.5 km, the Lærdal Tunnel currently under construction in western Norway will by far be the world’s longest road tunnel when completed.

The length and depth of tunnels today has also led to new requirements concerning drainage, tunnel lining and air quality. Norwegian expertise such as CTA International’s electrostatic dust precipitation technology is increasingly in demand on the global market. The Norwegian Tunnelling Society (NFF) issues a number of publications on Norwegian tunnelling expertise, and provides information regarding Norwegian firms and contractors. Members of NFF have participated in international tunnelling projects throughout the world.

Making the Connection

The need to cross the fjords has made Norwegian road builders experts in the utilization of a wide variety of bridge concepts. Norwegian contractors have extensive experience in the construction of suspension bridges with spans of up to 850 m. In the past ten years, Norway has erected several free cantilever concrete box girder bridges, two of which had record-breaking main spans (230 and 260 m, respectively) at the time of construction. Three new bridges of the same type are currently under construction, all with a main span close to 300 m. A number of wide-span cable stayed bridges have also been constructed, and have won international acclaim for their supple beauty. And new wood lamination technology has led to a revival for timber bridge structures in Norway and abroad.

The latest innovation in bridge-building involves a unique, Norwegian-developed floating bridge without lateral anchoring. So far, this concept has been used in two wide strait crossings, spanning 930 and 1,246 m respectively. The concrete pontoons utilized in this pioneering design have their origin in structures developed for the North Sea offshore petroleum industry.

Norwegian firms are participating in major bridge-building projects all over the world. Norconsult AS, a multidisciplinary consulting firm, has taken Norwegian transport technology and solutions to all corners of the globe. Hordaland Mek. Verkstad AS is a major exporter of cable cranes, inspection trolleys and air spinning equipment for suspension cables, while NRS-Strukturas KS has supplied form travellers and launching girders to the building of several hundred bridges in over 20 countries.

Over and Under

A major project currently underway in Norway is the Oslo Fjord Connection (see map above), a road network encompassing seven bridges and six tunnels designed to connect the eastern and western shores of the Oslo Fjord. The project is a challenge to planners and construction experts. At 7230 m, the longest tunnel is the Oslo Fjord Tunnel, which will run under the waters of the Oslo Fjord. With a gradient of seven per cent descending to 130 m below sea level, the tunnel has been the focus of some controversy. However, both critics and advocates agree that, when finished in the year 2000, this road network will enable private motorists and professional transporters alike to save several hours travel time by bypassing the downtown Oslo traffic.

Great importance has been attached to the aesthetic aspects of the new road network. Landscape architects have been involved in the planning process to ensure that the road and all related structures are functional and fit well into the landscape. The tunnels will be well lit, and the walls will be brightly painted to make travelling the Oslo Fjord Connection as pleasant an experience as possible.