Search

As offshore wind farms move into deeper waters and the capacity of offshore wind turbines (OWTs) increases, a new type of OWT foundation needs to be developed. In this study, a new type of five-bucket jacket foundation (FBJF) was proposed based on the broad application of a multi-bucket jacket foundation (MBJF) in offshore wind farms. The soil around the OWT foundation is subject to scour due to the complex marine environment. To investigate the effects of scouring on the FBJF, a series of local-scour simplified finite-element models of the FBJF were established using ABAQUS, and the effects of scouring depth and the extent on the bearing capacity of the FBJF with the monotonic load were analyzed. Then, the failure envelopes of the FBJF under combined loading were obtained using the fixed-displacement ratio method, and the effects of various scour conditions on the failure envelopes were compared. The results indicate that the failure envelope profile contracts inward, and the bearing capacity decreases with the increasing scouring depth and extent. Furthermore, the failure envelopes of the FBJF under different vertical loads were calculated, and the FV-FH-FM failure envelopes of the FBJF were obtained through interpolation. Finally, the effects of different scour conditions on the FV-FH-FM failure envelopes of the FBJF were analyzed. The results show that the FV-FH-FM failure envelopes of the FBJF have similar profiles and follow the same trend under different scour conditions. [ABSTRACT FROM AUTHOR]

To enhance the safety of the in-water sinking operation for an integrated system, including a bucket foundation (BF), tower, and rotor nacelle assembly (RNA), in complex marine environmental conditions, a model test of in-water sinking for an offshore wind turbine and bucket foundation (OWT–BF) is conducted. The motion behavior of the OWT–BF and the sling tensions during the in-water sinking process are investigated, and the numerical method is validated through test results. The results demonstrate a positive correlation between the wave height and motion response of the OWT–BF. The most critical stage of the in-water sinking operation occurs when the top cover of the bucket is fully submerged, resulting from the substantial cross-sectional difference between the bucket base and the transition section. Furthermore, the closer the OWT–BF is to the seabed, the less it is affected by waves in terms of motion response. It is advisable to conduct the in-water sinking operation of the OWT–BF in sea states with wave heights below 1.5 m. Simultaneously, slings can efficiently control the motion response of the OWT–BF, thereby enhancing the safety of the sinking operation. [ABSTRACT FROM AUTHOR]

As a form of clean and low-carbon green energy, offshore wind power occupies an important position in the global energy structure. With the rapid development of the wind power industry, wind power projects gradually develop from offshore to far-offshore sea areas. The multi-bucket jacket foundation is a considerable foundation type for far off-shore projects, but high installation costs involving ship transportation with parted components and field installation has significantly hindered its wide application. In this study, based on a 6.7-MW triple-bucket jacket foundation (TBJF) project of a deep-sea wind farm in China, a new integrated wet-towing method of "jacket + triple-bucket foundation" composite structure was proposed, which is suitable for far long-distance transportation of far-offshore applications. The static-model test of both self-stability and wet-towing stability was conducted. Based on the test and the numerical results, the natural period of the foundation for different draft depths in hydrostatic water and the stability for different eccentric loads were first evaluated. Then, the effects of different wet-towing modes and sea conditions on the stability of the TBJF were investigated. Finally, the optimal wet-towing mode and applicable sea conditions for the TBJF structure were proposed. [ABSTRACT FROM AUTHOR]

Efficient installation technologies for foundations and integrated offshore wind turbines play an important role in reducing the construction costs of offshore wind farms. The paper proposes a concept of a multi-bucket foundation floating platform (MBFFP) for the simultaneous transport of several bucket foundation-tower-turbine (BFTT) units, which relies on the fact that the bucket foundation can be prefabricated in bulk onshore and has reasonable floating stability. In addition, preliminary feasibility studies are carried out on static stability characteristics, hydrodynamic characteristics, multi-body coupling characteristics, and structural reliability. Firstly, the MBFFP concept is developed by drawing on our team's existing engineering experience of floating platforms and on-site monitoring data, with the objective of large-scale transport and installation of BFTTs. Next, the BFTTs transportation and installation method are presented. The static stability, hydrodynamic and multi-body coupling characteristics of the MBFFP are systematically studied based on numerical simulation methods, and the strategies of foundation shipment, integrated transportation, and multi-body coupling are proposed. Finally, a SESAM-ABAQUS co-simulation method is used to investigate the spatial distribution of structural stresses and the time history of nacelle vibration acceleration at different drafts, wave heights, and wave periods. The suitable operating sea conditions are summarized based on the nacelle acceleration limits and material ultimate strength. The results show that the roll and pitch of the MBFFP during floating do not exceed 2.5° and the stresses in all parts of the structure during installation are below 250 MPa at 2.5 m significant wave height and 11 s peak period, which indicates preliminary technical feasibility. Compared with traditional installation techniques, the proposed structure and method will contribute to the efficient transportation and installation of BFTTs. • Proposed concept & method for simultaneous transport of multiple BFTTs. • Future potential: Large-scale transport & quick installation of multi-bucket foundations with integrated turbines. • Verified preliminary feasibility for static stability, hydrodynamics, multi-body coupling, and bearing capacity. [ABSTRACT FROM AUTHOR]

By taking the importance of seepage parameters into account during the suction process, a comparison analysis of seepage field between bucket foundations with (C-BF) and without multiple subdivisions inside (N-BF) is performed in this paper, with the consideration of tilt adjustment as well as the complexity in underwater soil. Scaled model experiments were conducted at first to acquire the excess pore water pressure μ e , and then the law of three-dimensional heat conduction was used to simulate the seepage field and the parameters of the two models. The results of simulations were compared with those of the model experiment, and it is shown that the computational results agree well with those of experiments; N-BF is more sensitive to the tilting of the bucket body than C-BF; the layered soil can protect the seepage filled with limited hydraulic gradient and seepage flux; basically the seepage field variations with the same internal structure under different working conditions have their own regularities. [ABSTRACT FROM AUTHOR]

The integrated transportation of offshore wind turbine (OWT) and bucket foundation (BF) has obvious advantages in the application of shallow sea (<20m) wind farm engineering. However, this approach will face more challenges when it is applied to distant and deep-sea wind farms. In this study, a U and K shaped assembled platform (U&KSAP) is proposed and introduced for the first time, which is used to transport and install the OWT and BF (OWT&BF) in deeper and farther offshore wind farms. Firstly, the integrated transportation and installation method of OWT&BF based on the novel U&KSAP is discussed. The monitoring and brief analysis of U&KSAP and BF for the first sea transportation was carried out, and some key parameters were obtained. Secondly, the integrated transportation experiments of U&KSAP and OWT&BF were carried out in a towing tank. Finally, the main factors affecting the motion behavior of the integrated transportation process were discussed. The experimental results show that the U&KSAP has good seakeeping and is capable of integrated transportation. During integrated transportation, the influence of towing speed on drag resistance is obvious. The motion behavior of OWT&BF and U&KSAP is more sensitive to wave height and period, especially near the resonant period. The increase in towing speed and the air pressure inside the BF can slightly reduce motion response. At the same time, certain control measures should be taken for the top wind turbine to reduce horizontal acceleration during integrated transportation. • A novel integrated transportation and installation method of offshore wind power is proposed. • The first long-distance transportation process of U and K shaped assembled platform and bucket foundation is introduced. • The model experiment of integrated transportation of offshore wind turbine and bucket foundation is carried out. • Sensitivity analysis is conducted to evaluate different parameters of the integrated transportation process. [ABSTRACT FROM AUTHOR]