Case studies on suction caisson foundations in offshore wind farms in China

Suction caissons are cylindrical-shaped foundation elements closed at the top and open at the bottom which are almost completely embedded with their cylindrical part in the soil. The main advantage of this foundation compared to other commonly used foundation concepts is its fast, ease, and almost noiseless installation, as well as the effortless removal at the end of the lifetime. Suction caissons supporting three- or four-legged jackets have been employed successfully in several recent offshore windfarm projects around the world. The study presented herein investigates the general suitability of suction caissons in the south china sea at three representative sites. The results show that suction caisson foundations are technically feasible. Sizes can be large and may vary between 13 m to 15 m in diameter and 10 m to 13 m in length, which, however, may reduce noticeably when considering load redistribution in the design, typically done in a FEED and detailed design. The main challenges of suction caisson application are the very soft soil conditions and possible liquefaction potential due to large earthquake events. Although technically feasible, the economic viability of suction caissons needs to be investigated on project-specific basis. For that purpose, the authors provide an overview of general aspects which need to be considered in such an evaluation. This study gives realistic case studies for research and industry in offshore wind farm development.