The fat of the land

Environmental challenges and a unique geology have delayed construction of the planned 19-km fixed link between Roedbyhavn in Denmark and Fehmarn in Germany. The options of a bridge or a tunnel have been considered. In the tunnel option, four running tunnels would be required for both road and rail traffic, and the excavation would cause considerable environmental impact. With a cable stayed bridge, cast in situ concrete or steel piles to depths of 25m would be required. the ground investigation process has found an unusually high level of fat clays which have a liquid limit of over 50, and are some of the most extreme in Europe with a plasticity of around 150. The fat clays that lie around the island of Fehmarn have a flow problem since they have been dislocated by glaciers. A false tunnel of 50,000m3 has been excavated to monitor the behaviour of the clay and steel and concrete pile tests are also in progress. It is planned to complete the link in 2018.