Lateral bearing capacity and calculation method of pile-bucket foundation in clay for offshore wind turbines

Abstract

Pile-bucket foundation, which attaches a wide-shallow bucket to the head of monopile, has been proposed for offshore wind turbines to improve the bearing performance of monopile foundation. In this paper, model tests were firstly conducted to investigate the lateral bearing capacities of monopile, mono-bucket and pile-bucket foundations, as well as providing a validation to finite element (FE) analysis. The results show that the bucket can effectively enhance the lateral bearing performance of the monopile foundation. Next, according to a series of finite element analysis, p-y curves in both reinforced section and non-reinforced section of pile component in pile-bucket foundation are modified considering the influence of the bucket component. The moment and lateral resistance provided by bucket component are calculated by limit equilibrium method. Consequently, by regarding the contribution of bucket as a restoring moment and lateral load, the pile-bucket is converted to a pile with external moment and lateral load acting on the pile head. A theoretical calculation method of pile-bucket foundation subjected to lateral loads is put forward based on modified p-y curves. This method is validated by FE results and can provide estimations of lateral loads and deflections for pile-bucket foundations under lateral loading in engineering design.