Drilled and driven piles - Tangenvika Bridge in Norway

Increased requirements for rail transport north of Oslo have forced Norwegian Authorities to invest in the development of double-track rail to decrease traveling time and increase the frequency of the rail service. Part of this development is Tangenvika Bridge which is built on the largest lake and drinking water reservoir in Norway (Mjøsa). Once completed, it will be the longest railway bridge in Norway. The foundation design consists of drilled and driven composite piles. All the works are performed on water and because of its depth, all piles are installed from floating container pontoons instead of jack-up barges. In order to meet the strict steel quality requirements of composite piles, all piles are welded on land in a controlled environment and then transferred onto the transfer pontoons on water. Close to shores, due to the local presence of sensitive soils and the risk of underwater landslides, a total of 78 drilled piles (1016mm) are executed using the reverse circulation method (RC). All piles are drilled 2m into bedrock using a fully integrated ring bit system. In the deepest parts of the lake, a total of 60 driven piles (1430mm) are installed using 350kJ hydrohammer. The bottom of the piles are finished with a closed-ended pile tip, which is the most popular driven pile tip in Norway. All drilled and driven piles are installed in single lengths of up to 85m and net weight of 102t at 1:5 inclination. The lifting process of the piles on the water provides significant challenges for which a combination of 400t crane, 2 transfer pontoons, and a tugboat is used to provide a safe execution method.