Øresund Tunnel

The Øresund crossing connects Copenhagen Airport to the city of Lernaken, south of Malmö. It includes, in succession, a tunnel, an artificial island, a viaduct, a cable-stayed bridge, and a second viaduct. The infrastructure, which as a whole extends over a distance of 16 kilometres and accommodates both a highway and a rail line, is the result of 3 major contracts. The first contract called for the construction of a tunnel, the second for dredging operations, and the third for a bridge. VINCI Construction Grands Projets was mandated to design-build the tunnel. To be more specific, this project included construction of an submerged tunnel 3,510 metres long enclosing a dual 2-lane highway and double-track rail line (making it then the longest structure of its kind in the world). The tunnel includes gateways and access ramps at both extremities, technical buildings housing the ventilation systems, and exits linking to road and rail networks.

BACKGROUND

Øresund is the name of the strait that separates Denmark from Sweden. The project of building a permanent link between these two countries aimed to make the strait a hub for visitors from western Europe travelling to Sweden, Norway, and Finland. It all began in 2000, the fixed link crossing the Sund was inaugurated or rather, over a century ago, when some people were already envisioning bringing these 2 enemy regions together as part of a strategic alliance. In earlier times, ferries made the crossing, following 2 itineraries: the Storebælt crossing to get to the island of Sjælland (Copenhagen) and the Øresund crossing to get to Sweden. The project was designed to replace the ferries with a set of bridges and tunnels providing direct road and rail access.
The suspended bridge connects the city of Malmö to the artificial island of Peberholm. At one end of the island, roads and rail run under a channel into the tunnel that leads to Copenhagen.

TECHNICAL OVERVIEW

We prefabricated the tunnel components in a yard located at the northern end of the port of Copenhagen. We used a completely original fabrication process. To meet very constraining specifications regarding cracking caused by heat gradients in concrete, we decided to pour, in a single phase, tunnel segments 22 metres long in a controlled and homogeneous setting, that is, in a factory. We then used the incrementally launched bridge method. Each 176-metre caisson consisted of 8 segments about 22 metres long and 9 metres high, poured in a single phase, produced and line-assembled with dry joints equipped with shear keys to allow small rotational movements between them. Every time a segment was poured, the structure was shifted out of the factory to a finishing area located inside a submersible enclosure. Once the caisson was completed and sealed at each end, we filled the enclosure with water until the caisson floated. We then moved it to a deep basin. The submersible enclosure was then voided so that the caisson was left floating over the basin, which was connected to the sea.
The caisson, which was equipped with pontoons to support it during submersion, left the yard. It was then towed and placed in contact with the last submerged component. The caisson was maintained in position by a system of anchors, with assistance from a satellite-assisted Differential Global Positioning System (DGPS). This system, available in Denmark, gave us a level of accuracy to less than 50 millimetres. The caisson was then placed over jacks to set it in its final position. With the final setting in place, we backfilled the lower part with sand injection in the bottom of the caisson. The trench was then filled and we covered the top of the caisson with protective riprap.

The Drogden tunnel is 4 kilometres long, that is, 3.5 kilometres submerged and 500 metres of tunnel access. We chose a tunnel over a bridge for this part of the project because of the proximity of Copenhagen Airport and our wish to prevent bridge-aeroplane collisions however hypothetical the risk. This bridge-tunnel complex is both a technological and architectural feat.

IMPACT

Thanks to its oversized dimensions, this submerged tunnel was a world first. The structure connecting Denmark and Sweden was launched in July 2000. As a symbol of longstanding Nordic unity, the Øresund bridge-tunnel complex is an outstanding engineering achievement. It connects the cities of Malmö and Copenhague, the countries of Denmark and Sweden, and the Scandinavian peninsula with the rest of Europe.
In addition, this infrastructure helped create skill sets and economic trade where there were nearly none previously. It also fostered inter-city alliances such as Göteborg-Oslo (for biotechnology) and Stockholm-Helsinki (telecommunications).
Throughout the history of Scandinavia, the Sund Strait was a place of conflict. Today, the Øresund region has transformed itself into a hub for growth and competitiveness.
Thanks to this public utility, thousands of Scanians have been able to find work on the Danish coast. And thousands of Danes have left the saturated housing market in and around Copenhagen for better living conditions and better quality of life in Malmö. In fact, in 2008, nearly 6,000 Swedes began to work in Denmark.
The artificial island of Peberholm, which was created to provide a transition point between the bridge and the tunnel, has become a true haven for fauna and flora – and the biologists who study them. In fact, a botanical association has found more than 500 different species of plants on the island, which is also home to birds and a rare species of green toad.
Sixteen years after delivering the Øresund tunnel, VINCI Construction Grands Projets is leading a consortium that has won the call for tenders to build the Femern submerged tunnel designed to connect Denmark and Germany.