K12 – Marine geotechnical design
This report describes the geotechnical design for the recommended bridge concept K12. The K12 concept is an end-anchored floating bridge with mooring system for increased robustness and redundancy. There is a pylon support at Svarvhelleholmen in south, and a filling at Gullholmane in the north. Mooring pontoons are at two locations, with 4 anchors in each direction, which gives 16 anchor locations in total. The bathymetry of Bjørnafjorden is characterized by steep slopes in the south and a hilly seabed in the north, with ridges and valleys. The mid part basin is covered by slightly overconsolidated soft clay down to more 50 meters depth. The sediment thickness is varying from 0 to about 80 m. The hilly and steep areas are partly covered by soil, with bedrock outcrops. So far the soil investigations indicate soft soil of the same character in those areas as in the basin. The fjord is characterized by many old landslides, which can clearly be seen on the maps from subsea surveys.