News, Rock Engineering

Making Connections

Norway has invested a great deal in its road infrastructure to tie together the country's widespread population through difficult terrain. In order to provide a comprehensive road network, engineers and contractors have had to devise bridges across fjords - to...

Norwegian road builders have constructed some 17,000 bridges to cross the country’s many waterways. And since no two fjords are alike, they have become expert at utilizing a wide variety of bridge concepts. Suspension bridges, with spans as broad as 800 m, have become a Norwegian speciality, as have wide-span cable-stayed bridges, which have won international acclaim for their suppleness and beauty. More than 100 free-cantilever bridges have been built in Norway, which is also home to the world’s longest pre-stressed concrete girder bridge – the Stolmasund Bridge near Bergen, with a 301 m span.

The latest innovation in Norwegian bridge building is the development of a floating bridge without lateral anchoring. So far, this concept – which is technically a hybrid of a bridge and an offshore structure – has been used in two wide strait crossings, the Bergsøysund Bridge (930 m) and the Nordhordland Bridge (1,246 m).

Crossing the Oslo Fjord

Thanks to advanced Norwegian tunnelling technology, tunnels have become a viable, cost-effective alternative to building roads above ground in difficult terrain and through urban centres. One of the major road projects in Norway at the turn of the 20th Century is the Oslo Fjord Crossing, which will provide an improved link between the eastern and western sides of the fjord and faster routes to Sweden and the rest of Europe by bypassing downtown Oslo. The project covers a total distance of 26.5 km, and includes seven bridges and six tunnels, one of which is a 7.2-km-long subsea tunnel. The subsea tunnel has a maximum hill gradient of seven per cent, and runs 130 m below sea level at its lowest point.

Much of the Oslo Fjord Crossing weaves through untouched woodlands. To ensure that design and building materials harmonize with the land and seascapes, wood and local rock have been used to construct or decorate overpasses, tunnel entrances and dividing walls. To avoid damaging the woodlands, the road has been placed in a 1.3-km-long tunnel through the most unspoiled areas, with an overpass for wildlife such as moose and deer. Sheltered rest stops will be built in areas with dense vegetation and attractive fjords views to provide motorists with a pleasant place to take a break.

Safe, Clean Traffic Flow

Proper lighting and ventilation are vital to traffic safety in road tunnels. In Norway, 90 per cent of all road tunnels 100 m and longer are lighted, and close to 60 per cent are mechanically ventilated. The two-lane 24.5-km-long Lærdal Tunnel, scheduled to open at the end of 2000, will be the world’s longest road tunnel. It is equipped with a unique filtration and cleaning system developed by the Norwegian Public Roads Administration (NPRA) and ABB Alstom Power. The system makes it possible to provide long tunnels with air that is as clean or cleaner than the air in short tunnels. Between 90 and 95 per cent of the dust, exhaust particles and NOx emissions in the tunnel will be removed by the system, which features a special catalytic filter (patent pending).

The Norwegian road authorities and contractors have gone to great lengths to make the 20-minute drive through the Lærdal Tunnel safe and enjoyable. To help to keep motorists alert, 55 W fluorescent tube lamps will be installed every 18 m, and colourful artwork will pride the tunnel walls. Semicircular turnabouts excavated every six km will also help to break up the monotony of the journey, and allow large vehicles to turn around in the event of an emergency

Electronics Experts

Norway is a world leader in the use of electronic traffic surveillance. Automated monitoring equipment has been installed in many locations, particularly in tunnels and at tunnel entrances, to identify motorists who exceed the speed limit. Automatic field stations feed the NPRA’s user-information service with vital data, providing motorists with continually updated information regarding weather and road conditions and the speed and flow of traffic. In the Lærdal Tunnel, antennas have been installed to serve emergency personnel and motorists using mobile phones.

Norway boasts years of experience with electronic toll collection systems. The Q-Free intelligent toll collection systems are based on surface acoustic waves, and are exported around the world, from Guangzhou, China, to Sao Paulo, Brazil. The company is now cooperating with the NPRA to develop new technology that will allow Norwegian motorists to drive through all of the country’s toll plazas with the use of a single contactless card. Norway is the first European country to define a standard for an entire nation; the project is a step toward the establishment of European standards and regulations for the use of IT in the transport sector. Such standards are expected to greatly facilitate international commercial road transport.