The Carbon Trust has published guidance on the geotechnical design and installation of suction caisson foundations to enhance confidence in their use by the offshore wind industry.
The Offshore Wind Accelerator (OWA) Suction Installed Caisson Foundation Design Guidelines brings together latest understanding and research to provide clarity and guidance for engineers looking to design suction caissons for foundations in offshore wind.
Suction-installed caissons have seen increased acceptance in the offshore wind industry due to their potential for low-noise and quick installation.
They are also suitable for certain challenging soil conditions, enabling suction caissons to compete on a commercial basis with traditional monopile and jacket designs.
At over one hundred pages the extensive document addresses key areas, starting with terminology of different types of suction caissons available, plus terms of key components used in their assembly and installation.
Another section deals with design principles, which cover a range of limit states, design optimisation, covering load and material factors for suction caissons for offshore wind turbines and also for offshore substations, as well as geotechnical conditions for suitable sites.
The guidelines also deal with installation design, including limits to suction pressures, as well as trial installations.
A section on installation operations covers areas including seabed preparation and scour protection, self-weight and suction-assisted penetration through to identifying various installation hazards, including instability during touch down and tilting of the structure.
The document also addresses decommissioning of suction caissons.
Cathie Associates is the lead author of the guidelines and Oxford University and SPT Offshore co-authored the document, which was reviewed by Lloyd’s Register.
The OWA has been instrumental in helping the commercialisation of suction-installed caissons, with Universal Foundation’s monobucket and SPT Offshore’s suction bucket jacket.
Today, suction-installed caissons are supporting the latest generation of 8MW turbines at Vattenfall’s European Offshore Deployment Centre in Scotland and Orsted’s Borkum Riffgrund 2 in Germany.
Cathie Associates senior engineer Jamie Irvine said: “The guidelines provide the industry with a long sought-after methodology that gives greater clarity to designers and developers on the key issues concerning the design of suction caissons.
He said the guidelines present the current state of knowledge and good industry practice for suction caisson foundation design.
“As lead authors, we hope this guidance enhances confidence in the use of suction caissons in the offshore wind industry and facilitates design and review process.”