Site investigation and soil parameters for offshore suction bucket design: A case study of Houhu wind turbine

The offshore wind farm industry in China has been growing exponentially in recent years, and suction bucket foundations are increasingly applied as an effective solution. This paper presents a comprehensive site investigation and outlines the key soil parameters for offshore suction bucket foundation design, by taking the Houhu wind farm in southern China as an example. The in-situ cone penetrometer (CPTU) tests and sampling borehole were carried out to investigate the geotechnical features of soils. The soil conditions are characterized by multilayers and complicated sediment components. The classification and mechanical properties, such as stress history, static and cyclic shear strengths, and shear modulus of soils were obtained and compared by CPTU interpretation and advanced laboratory tests. Then the probable foundation optimization design solution from the perspective of soil parameters in the light of set up effect and cyclic behavior was discussed and highlighted. Based on the experience of this project and other projects in offshore China, some common challenges were summarized and the relative recommendations were proposed finally. The main objective of this study is to provide more reliable guidance of geotechnical investigation for the rapid development of wind farms in offshore China.