Failure Envelopes of Composite Bucket Foundation for Offshore Wind Turbines under Combined Loading with considering Different Scour Depths

Yuanxu Jing,Lunbo Luo,Jingqi Huang,Yuan Wang,Wei Wang,Piguang Wang

doi:10.1155/2021/7922572

Abstract

The composite bucket foundation of offshore wind turbines is subjected to a variety of loads in the marine environment, such as horizontal load H, vertical load V , bending moment M, and torque T. In addition, due to the characteristics of its connection section, the water flow around the foundation will produce scour pits of various degrees, reducing the depth of the bucket foundation, which has a nonnegligible impact on the overall stability of the bucket foundation. In this paper, the failure envelope characteristics of different combinations of loads on bucket foundations, including V -H-T, V -M-T, conventional V -H-M, and noncoplanar V -H-M, are numerically investigated with considering different scour depths. The numerical results indicate that the V -H-T, V -M-T, conventional V -H-M, and noncongruent V -H-M failure envelopes gradually shrink inwards with increasing scour depth, and the stability of the composite bucket foundation decreases; the conventional V -H-M failure envelope shows an asymmetry of convexity to the right, and the noncongruent V -H-M failure envelope shows an asymmetry of outward convexity to the left and right. The corresponding mathematical expressions for the failure envelope are obtained through the normalized fitting process, which can be used to evaluate the stability of the bucket foundation based on the relative relationship between the failure envelope and the actual load conditions, which can provide practical guidance for engineering design.

Highlights

As a clean and renewable energy source, offshore wind power is rapidly developing due to its advantages of less turbulence, not occupying arable land, and less impact on the environment [1, 2]
In the actual marine environment, the composite bucket foundation is subjected to a complex load situation, by the longterm self-weight load V of the wind turbine superstructure and by the horizontal load H, the moment load M, and the torque load T transmitted by the wind turbine blade structure [8,9,10]. erefore, the bearing capability of the composite bucket foundation is an important problem in offshore wind power engineering
Unidirectional Ultimate Bearing Capacity of Composite Bucket Foundations under Different Vertical Loads. e ultimate bearing capacity of a composite bucket foundation loaded in one direction with a displacement-controlled

Summary

Introduction

As a clean and renewable energy source, offshore wind power is rapidly developing due to its advantages of less turbulence, not occupying arable land, and less impact on the environment [1, 2]. In the actual marine environment, the composite bucket foundation is subjected to a complex load situation, by the longterm self-weight load V of the wind turbine superstructure and by the horizontal load H, the moment load M, and the torque load T transmitted by the wind turbine blade structure [8,9,10]. Erefore, the bearing capability of the composite bucket foundation is an important problem in offshore wind power engineering. Liu et al [12] investigated the ultimate bearing capacity of the composite bucket foundation under vertical loading with the aid of the model test and classical plasticity theory. Liu et al [13] studied the horizontal bearing capacity characteristics of the composite bucket foundation in silty clay soil through a large size model test. Liu et al [13] studied the horizontal bearing capacity characteristics of the composite bucket foundation in silty clay soil through a large size model test. e distribution law of earth pressure, the

Methods

Results

Conclusion