Reduction in soil penetration resistance for suction-assisted installation of bucket foundation in sand

Bucket foundation is recently consider as a cost-effective solution for offshore wind turbines. However, the concept requires still a better understanding and a full design method that can be approved by standards. 1G laboratory tests for the installation of medium-scale bucket foundation have been performed in the laboratory of Aalborg University, Denmark. The main purpose of those tests is to investigate the interaction between the soil and the bucket skirt during the jacking and the suction installation process. The most often proposed method for the penetration resistance during installation of bucket foundation is a CPT-based method. The calculation requires information about empirical coefficients kp and kf , relating the skirt tip resistance and the skirt friction to the cone resistance measured during Cone Penetration Test, CPT. What is more, the suction-assisted installation in permeable soil adds additional parameters into the design resulting from the induced seepage flow around the bucket skirt. β-parameters introduced into the design describe a reduction in soil penetration resistance due to this flow. As an effect of tests results analysis, empirical coefficients and β-parameters are proposed. The use of those values leads to a reasonable fit between the applied force and the calculated soil resistance based on CPT, therefore, brings closer to the full design method for the suction
installation of bucket foundation.