There are overlying soft soil layers in most offshore sites of China

which is disadvantageous to the construction of offshore wind farms. To investigate the effect of overlying soft clay on the bearing characteristics of pile-bucket composite foundation for offshore wind turbines

we established numerical analysis models for pile-bucket composite foundation in the overlying soft clay with different thicknesses. The bearing characteristics were analyzed under unidirectional loading (V

H

M) and combined loading (H-M) by using finite element software ABAQUS. The influences of the thickness of overlying soft clay on the ultimate bearing capacity in all directions

the bearing capacity sharing ratio of different structures of pile-bucket composite foundation

and the initial stiffness kinit were studied. Results show that the ultimate bearing capacity of pile-bucket composite foundation in all directions gradually decreased with the increase in the thickness of overlying soft clay. When the thickness of overlying soft clay was 6 m (equal to the inserted depth of bucket penetration)

the vertical ultimate bearing capacity of pile-bucket composite foundation was reduced by 12.86%

the horizontal ultimate bearing capacity was reduced by 46.55%

and the ultimate moment capacity was reduced by 34.86%. The initial stiffness kinit of pile-bucket composite foundation decreased with the increase in the thickness of the overlying soft clay. In summary

the effect of the overlying soft clay on the bearing characteristics of pile-bucket composite foundation should be taken into consideration in the design of foundations for offshore wind turbines.