Abstract: Compared with traditional offshore foundation structure, bucket foundations which are large cylindrical structures open at the base and close at the top may realize economical advantages over traditional driven piles due to the speed of installation, elimination of the pile driving process, and reduction in quantities and material costs. Though bucket foundation is a new foundation type for offshore wind turbine, there have no standards for bucket foundation designing up to now. In designing the bucket foundation, the simplified limit equilibrium method is usually adopted, in which the soil inside the bucket and the skirt of the bucket are assumed to form a whole foundation. But this method cannot reflect the working mechanism of the internal soil. Based on a foundation of offshore wind turbine in Fujian, adopting the finite element software ABAQUS, the three-dimensional numerical analysis is performed to simulate the working mechanism and evaluate the bearing capacity behavior of bucket foundation. According to the bearing capacity of offshore wind turbine, the simplified model and models with or without compartments are established with the considering of the compartments effect. According to calculation results, the bearing characteristic of the bucket foundation is different from the simplified limit equilibrium method that the internal soil of the foundation yields first in the loading process. The difference leads the simplified limit equilibrium method will over estimate the bearing capacity of bucket foundation. In addition, the error of the bearing capacity calculated by the simplified limit equilibrium method is estimated. The suggestion about the bearing capacity of bucket foundation has reference value to project designer.

Key words: bucket foundation, working mechanism, bearing capacity, limit equilibrium, finite elements