• Journal of the Korean GEO-environmental Society
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• v.15 no.6
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• pp.75-83
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• 2014

Suction bucket foundation is installed with the differential pressure created by pumping water out of bucket. Bucket foundation has usually been utilized in mooring anchor for offshore platform or floating oil and gas production facilities in the open sea. After suction bucket foundation successfully was applied as the foundation for offshore wind turbines in Europe, it recently attracts much attention in Korea, too. To estimate the penetration resistance of the suction bucket foundation is one of the important matters that should be considered during its installation. This study carried out a series of model tests to investigate the penetration resistance of suction bucket foundation. And the mobilized soil strength factor was reviewed through comparing the experimental results by two installation ways (e.g., push-in-load and suction) and the results calculated by the conventional equation.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.1
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• pp.31-36
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• 2022

This paper presents the measuring process of dynamic properties of offshore wind power foundation and provides consideration of each step. This Guideline enables to maintain consistent measuring procedure and therefore increase the reliability of test results. Small scaled suction bucket foundation was fabricated to represent the commercial support structure installation mechanism and two cases(free-free, free-fixed) of dynamic tests were performed at workshop. From the tests, the importance of dynamic properties of connection part between suction bucket and tower was figured out. More over, types and configuration of measuring devices are recommended which can help find the natural frequency of wind turbine foundation correctly. In field test, it was found that the natural frequency of suction bucket foundation was increased linearly with the penetration depth due to the confining effect of ambient soil. Meanwhile, it was not easy to get an enough excitation force with normal impact hammer because the N.F of suction bucket model was in the lower range of 0 Hz ~ 5 Hz. Therefore, new excitation method which has enough force and can excite lower frequency range was devised. This study will help develop safety check procedure of suction bucket foundation in field at each installation stage using the N.F measurement.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.61-73
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• 2023

Suction buckets are feasible options for offshore foundations to support subsea structures in deep water, enabling suction-induced installation by pumps. Recently, hybrid suction bucket foundations that combine single or multiple suction buckets with a mat foundation have been considered. The foundations effectively increase the load capacity while reducing construction costs. However, there is still insufficient experimental validation of hybrid suction bucket foundations regarding their bearing capacity. Furthermore, research on the horizontal load capacity under low vertical and moment loads is inadequate. In this study, we investigate the feasibility of using a hybrid suction bucket foundation for subsea installations in clay. We considered two types of hybrid suction bucket foundations: a circular mat with a single suction bucket and a square mat with multiple buckets. Centrifuge tests were performed to understand the hybrid suction bucket foundation characteristics under horizontal loads and their corresponding bearing capacity. Particularly, we verified the effect of the mat foundation and bucket embedment depth on the horizontal bearing mechanism and capacities. Results confirmed that the hybrid suction bucket foundation outperforms the single suction bucket.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.69-78
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• 2016

A suction bucket foundation has been considered to be a potential foundation type for offshore wind turbines. A suction bucket foundation is usually installed in soft soil, so the accumulated displacement of the foundation may occur under long-term cyclic loads. In this study, a series of 1-g model tests were performed to analyze the accumulated rotation of suction bucket foundations under long-term cyclic horizontal loads. The dry model ground was prepared to have two different soil densities by air-pluviation method. The model tests were performed varying the embedment depth of the suction bucket, the soil density, and the amplitude of cyclic load. A one-way horizontal cyclic load was applied over $10^4$ cycles. Test results showed that the accumulated rotation of the suction bucket foundation increased with the increase in the number of cycles and load magnitudes. Based on the model test results, a new equation was proposed to evaluate the accumulated rotation of the suction bucket foundations in dry sandy ground under long-term cyclic horizontal loads.

• New & Renewable Energy
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• v.6 no.3
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• pp.47-54
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• 2010

Foundation plays an important role in the offshore wind turbine system. Different from conventional foundations, the suction caisson is proven to be economical and reliable. In this work, three-dimensional finite element method is used to check the suitability of suction caisson foundation. NREL 5MW wind turbine is chosen as a baseline model in our simulation. The maximum overturning moment and vertical load at the mudline are calculated using FAST and Bladed. Meanwhile the soil-structure interaction response from our simulation is also compared with the experiment data from Oxford university. The design parameter such as caisson length, diameter of skirt and spacing of multipod are investigated. Accordingly based on these parameters suggestions are given to use suction caisson foundations more efficiently.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.494-503
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• 2010

This paper reviews research trend in suction bucket foundation. Wind energy farm has been considered as an efficient alternative to fuel energy as world markets attempt to discover renewable resources. Recently, Korean government initiated the research projects investigating installation method of offshore wind energy foundation and design guideline as well as verifying feasibility of offshore wind farm. In fact, the installation of monopile and gravity type foundation has been sucessfully carried out in European and other advanced countries, and design guideline of those foundations are well established; however, various types of foundation would be necessary in the near future as offshore wind farm demands abundant wind resources in deep sea. In this paper, bucket foundation is spot lighted as a powerful and economic alternative applicable to deep sea condition.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.4
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• pp.202-211
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• 2016

This study aims to analyze seismic responses of suction foundations for offshore wind turbine. For this purpose, dynamic centrifuge model tests were carried out. The skirt length of the suction foundation is a critical element for bearing mechanism against environmental loads. Thus, dynamic centrifuge model tests were performed and analyzed for three suction foundation models with the ratios of skirt length to suction foundation diameter of 0.5, 0.75, and 1 installed in dense sand. As results, the acceleration amplification at the suction foundation, residual settlement, and residual tilting angle were compared.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.825-839
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• 2010

The global and domestic market for offshore wind farm is expected to grow fast, and the design and installation of substructure and foundation is getting more important. As for the offshore wind farms located in the shallow(depth < 20m) water, the construction and installation of the substructure and foundation makes up about 1/4 ~1/3 of the offshore wind farm construction cost, and the portion is expected to increase because the turbine capacity is increasing from 2 ~ 3MW to 5MW or larger and the water depth of wind farms is also increasing over 30m. As a foundation for offshore wind turbine, the suction caisson foundation is being considered to be a highly competitive alternative to the conventional monopile or gravity based structure, because it has features suitable for the offshore construction such as quick installation, no heavy equipment for penetration and no hammering noise for driving. In order to study the installation behaviour of the suction caisson, laboratory tests were performed with sand. The pore water pressure and displacement were measured to analyze the suction pressure during penetration, the penetration speed and the amount of heaving.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.183.2-183.2
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• 2010

A three-dimensional numerical modeling using the finite element method for the suction caisson are described to decide suitability as foundation of offshore wind turbine in this paper. In the simulation, soil-structure interaction is defined by comparing experiment data. The reaction of monopod suction caisson is presented by moment loading which was calculated by FAST. Tendency of suction caisson appeared by difference of length and diameter of skirt under coupled loading. Length and diameter of skirt are suggested and evaluated as a offshore wind turbine.

• Journal of Ocean Engineering and Technology
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• v.38 no.2
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• pp.74-85
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• 2024

Offshore wind turbines are supported by various foundations, each with its considerations in design and construction. Gravity, monopile, and suction bucket foundations encounter geotechnical issues, while jacket and tripod foundations face fatigue problems. Considering this, a gravity foundation based on a steel skirt was developed, and a monopile foundation was analyzed for Pile-Soil Interaction using the p-y curve and 3D finite element method (3D FEM). In addition, for suction bucket foundations, the effects of lateral and vertical loads were analyzed using 3D FEM and centrifuge tests. Fatigue analysis for jacket and tripod foundations was conducted using a hotspot stress approach. Some hybrid foundations and shape optimization techniques that change the shape to complement the problems of each foundation described above were assessed. Hybrid foundations could increase lateral resistance compared to existing foundations because of the combined appendages, and optimization techniques could reduce costs by maximizing the efficiency of the structure or by reducing costs and weight. This paper presents the characteristics and research directions of the foundation through various studies on the foundation. In addition, the optimal design method is presented by explaining the problems of the foundation and suggesting ways to supplement them.