Suction bucket foundation is named by many experts in offshore geotechnics as an alternative to pile foundations for offshore wind turbines as it is often more cost-effective. The suction installation process is noise-free and requires less operational time. A simple design of suction bucket is a steel cylindrical thin structure. A significant increase in size of foundation requires a higher pressure for installation and, at the same time, increases the probability of buckling failure. The proposed modular bucket consists of trapezoidal wall sections that are convenient for industrialization. The structure is significantly thinner than a circular bucket, resulting in a weight saving of 28% for full scale model with diameter equal 8 m (EUDP, 2018). This design has been analyzed for buckling resistance and results in much better performance. The paper includes also the installation tests on a medium-scale bucket models, both the round and modular. Results prove that the initially large penetration resistance in sand is highly reduced by the seepage flow induced by applied suction. Moreover, the comparison of results shows that the extra increase in jacking required load for modular bucket due to larger area is minimized almost to no difference in the required suction between circular and modular bucket model. These findings can contribute to a significant decrease in energy production costs for offshore wind turbines allowing installation of bigger turbines with reduced cost of the foundations.
Aleksandra K. Koteras, Francisco M. G. Rodriguez and Lars B. Ibsen
Keywords: Modular bucket, Offshore wind turbines, Penetration resistance reduction
Publisher: DFI