Suction Installation of Modular Bucket Foundation for Large Offshore Wind Turbines-Paper

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The paper evaluates a modular suction bucket foundation as a potentially lower-cost alternative to monopiles for large offshore wind turbines. Its skirt is assembled from thin trapezoidal steel sections with internal stiffeners, making it suitable for industrial production and lighter than a conventional circular design. A full-scale design reportedly saves 28% of foundation weight.<br /><br />Laboratory installation tests compared medium-scale modular and circular buckets in dense sand, using both mechanical jacking and suction. Jacking tests showed substantially higher penetration resistance for the modular model, whose skirt has a larger area. During suction installation, however, seepage around the skirt reduces soil resistance, leaving the suction required by the two designs nearly equal. Suction also loosens the soil trapped inside the bucket, increasing its permeability.<br /><br />Finite-element buckling analysis found the modular bucket’s resistance to be about 2.7 times that of the circular model; internal stiffeners can improve it further. This greater resistance may permit higher installation pressures and use of thinner steel. The study also modeled seepage and critical suction pressure, and assessed a cone-penetration-test-based method for predicting installation resistance. The method did not perfectly match observed loads, suggesting that internal skirt friction and tip resistance should not be assumed to disappear entirely under suction.<br /><br />Overall, the results indicate that modular buckets could combine lower material use with installation performance comparable to circular buckets, supporting their potential for large offshore turbines. However, the critical-pressure predictions and resistance calculations require validation through full-scale testing.

Keywords

modular suction bucket

offshore wind turbine

foundation design

steel skirt sections

installation resistance

suction installation

buckling analysis

dense sand

seepage

full-scale testing