On behalf of Norther NV, a joint Venture of Electrawinds and Eneco, a preliminary geotechnical site investigation was completed at the Norther concession off the coast of Belgium near the port of Zeebrugge in water depths of up to 35m LAT. The client required 100mm diameter high quality samples from the clays and sands as well as CPTU test results allowing the engineer to complete the preliminary design of the turbine foundations.
The campaign incorporated 3 boreholes and 6 CPTU tests of up to 50m depth below seabed. The CPTU testing and sampling works were undertaken simultaneously from two moonpools provided on the self-elevating platform “Buzzard”. In stiff cohesive clays GeoborS triple wireline core drilling was used as sampling method providing 102mm diameter samples. The SONIC sampling method was used as sampling technique in non-cohesive materials (e.g.gravels and loose sands) providing high sample recovery rates. The self-elevating platform “Buzzard” was fitted with spud-cans reducing leg penetrations significantly.