Bearing Capacity of a Monopod Bucket Foundation for Offshore Wind Towers - Centrifuge and Numerical Modeling

The composite bucket foundation for offshore wind turbine bears the vertical load from not only the superstructure and the horizontal load, caused by wind and wave, but also from the torque load caused by rotating structures, such as blades. Based on layered soil foundation, the influence of the skirt height, the friction coefficient between soil and bucket foundation and the diameter of the bucket foundation on the stress of the bucket skirt under the torque load are studied in this paper. Moreover, the envelope curves of the bearing capacity of H–T and V–H–T are obtained by the fixed displacement ratio loading method. The bearing capacity characteristics of composite bucket foundation under different loading combinations are analyzed. The results show that: (1) The effect of inside soil on the bucket skirt is greater than that of the outside soil; (2) when composite loads are applied, the torque-bearing capacity decreases slowly with the increase of horizontal force, and when the horizontal force increases to a certain value, the value of the torque decreases significantly; and (3) the shape of the H–T failure envelope of the bucket foundation has no obvious change, vertical load have less effect on horizontal and torque load.

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Study on Effects of the Scouring on Horizontal Bearing Capacity of the Composite Bucket Foundation

Volume 10: Ocean Renewable Energy ◽

10.1115/omae2018-77370 ◽

2018 ◽

Author(s):

Ding Hongyan ◽

Zhao Xing ◽

Zhang Puyang ◽

Le Conghuan

Keyword(s):

Bearing Capacity ◽

Model Test ◽

Shallow Foundation ◽

Offshore Wind ◽

Physical Model Test ◽

3D Fem ◽

Foundation Soil ◽

Bucket Foundation ◽

Loading Mode ◽

Waves And Currents

Composite bucket foundation is a new kind of wide-shallow foundation for offshore wind turbines, and can be made on land, transported and installed by one step. Compared with other deep pile foundations, the erosion caused by waves and currents is more obvious and this would cause more risks for the overall safety of the wind turbine. In order to know more about it, a 3D FEM composite bucket foundation - soil model is established using Abaqus in this paper. In this study, the lateral bearing capacity of composite bucket foundation in different situation is analyzed by FEM and the results of FEM have been compared with that of physical model test. And through anther model test, the size parameters of scouring pit are obtained. Then the emergence and development of scouring pits are simulated by continuously excavating soil. The horizontal bearing capacity of a practical project is calculated considering the influence of scouring on the CBF by the displacement loading mode. The calculation results show that the horizontal bearing capacity of the bucket foundation is significantly reduced after scouring, and the influence of scour depth is more significant than the scouring extent.

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Upper Bound Solutions of Vertical Bearing Capacity of a New Type Bucket Foundation in Sand

Volume 3: Offshore Geotechnics ◽

10.1115/omae2014-24536 ◽

2014 ◽

Author(s):

Run Liu ◽

Guangsi Chen ◽

Hongyan Ding ◽

Jijian Lian

Keyword(s):

Bearing Capacity ◽

Wind Turbine ◽

Upper Bound ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Empirical Parameter ◽

Number Range ◽

Bucket Foundation ◽

Vertical Bearing ◽

Vertical Bearing Capacity

Offshore wind turbine is a new solution of the energy crisis, and stable foundation is an important guarantee for its safety. An important characteristic of wind turbine foundation is to bear the vertical load, horizontal load and moment at runtime. A large diameter wide-shallow bucket foundation, as a new foundation type, is proposed by Tianjin University for applying to the specific load conditions. The diameter of the foundation is generally more than 30 m, and its embedment ratio is between 0.2 and 0.5. Compared with other traditional forms of ocean engineering foundation, there have been no standards and theories for bucket foundation designing currently. The vertical bearing capacity is an important basic indicator in the process of offshore wind turbine foundation designing, which determines the size of wind turbines and the cost of engineering. This paper proposes two failure mechanisms about vertical bearing capacity of bucket foundation through the experiment. The upper value of vertical bearing capacity of bucket foundation has been derived through the upper bound theorem of classical plasticity theory. Soil damaging rate is specified as a new empirical parameter in the formula. It is defined as the rate between the thickness of the soil which is broken inside the foundation and the radius of foundation, which indicates the range of soil failure. And the number range of soil damaging rate is obtained through the vertical bearing capacity experiments. Relationship between bearing capacity factor Nγ and friction angle also discussed under the specific soil damaging rates. These results are helpful in reducing the uncertainties related to the method of analysis in bearing capacity calculations, paving the way for more cost-effective foundation design.

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