Effect of partial drainage on the pullout behaviour of a suction bucket foundation.

Suction-bucket-supported jacket foundations are being used increasingly for offshore wind turbines, the advantages being large bearing capacity and efficient installation. For a large-capacity wind turbine, the pullout capacity and displacement of the bucket in the tripod or tetrapod jacket can be critical to the safety of the structure. The loading rate, which is commonly dominated by the offshore environmental conditions, has a significant effect on the ultimate capacity and stiffness of the bucket foundation. In this paper, a numerical model is developed to investigate the response of a bucket foundation under vertical pullout loading at different rates. A bounding-surface model based on critical state soil mechanics is introduced to account for the soil behaviour under different stress states and drainage conditions. The model is modified and calibrated against a comprehensive set of laboratory tests, including both triaxial compression, triaxial extension and direct simple shear tests in drained and undrained conditions. How partial drainage affects the load–displacement response and pore pressure field are thus presented. A parametric study on the selection of soil parameters is also conducted to shed light on practical foundation design. [ABSTRACT FROM AUTHOR]