The Statpipe subsea shore approach bridge tunnel was constructed to protect the gas pipeline, coming from the Statfjord, Gullfaks and Veslefrikk fields and the export pipeline to the European continent. The gas is processed at KArst", Western Norway. The shore approach tunnel extends 600 m westward along the sea bottom into the North Sea. It was constructed as five simple supported elements of lengths from 80 to 150 metres. Within a few years after installation, the concrete started to diSintegrate by cracking, crushing and spalling. The damage became greater every year, and it became necessary to carry out extensive repair operations in 1991 and 1992. The damage was found to be caused by higher frictional forces than originally considered in the supports of the elements. The load effect causing this high frictional force was bending of the bridge tunnel elements about the vertical axis. In this paper the damage, environmental loads, design modifications and repair are presented. The repair consisted of installing new bearings and repair of damage to the concrete. The new bearing installation required the elements to be jacked 500 mm. The largest bridge tunnel element has a submerged weight up to 4200 tonnes. The installation of the bearings, weighing up to 5 tonnes, was performed by divers.
The pipeline system transports rich gas from the Statfjord, Gullfaks and Veslefrikk oil/gas fields in the North Sea to the Kårstø Gas Terminal where the heavy components are extracted and dry gas exported to the European continent. The particular nature of the Norwegian coastline is very different from what is seen along the German, Dutch, Belgian and UK coastlines. Presence of solid rock, moraine and soft sediments in between makes the seabed irregular and mostly unsuitable for conventional landfall solutions such as beach pull-in.