Horizontal Bearing Capacity of Monocolumn Composite Bucket Foundations for Offshore Wind Turbines

Abstract

Monocolumn composite bucket foundation is a new type of offshore wind energy foundation. Its bearing characteristics under shallow bedrock conditions and complex geological conditions have not been extensively studied. Therefore, to analyze its bearing characteristics under complex conditions—such as silty soil, chalky soil, and shallow bedrock—this paper employs finite element software to establish various soil combination scenarios. The load – displacement curves of the foundations under these scenarios are calculated to subsequently evaluate the horizontal ultimate bearing capacity. This study investigates the effects of shallow bedrock depth, the type of soil above the bedrock, the thickness of layered soil, and the quality of layered soil on the bearing characteristics of the monocolumn composite bucket foundation. Based on the principle of single-variable control, the ultimate bearing capacity characteristics of the foundation under different conditions are compared. The distribution of soil pressure inside and outside the bucket wall on the compressed side of the foundation, along with the plastic strain of the soil at the base of the foundation, is also analyzed. In conclusion, shallow bedrock somewhat reduces foundation bearing capacity. Under shallow bedrock conditions, the degree of influence on foundation bearing capacity characteristics can considerably vary on different upper soils. The thickness of each soil layer and the depth to bedrock in stratified soils also affect the bearing capacity of the foundation. The findings of this paper provide a theoretical reference for related foundation design and construction. In practice, the bearing performance of the foundation can be enhanced by improvingthe soil quality in the bucket, adjusting the penetration depth, adjusting the percentage of different types of soil layers in the bucket, and applying other technical construction methods.

Keywords

Monocolumn composite bucket foundations / Shallow bedrock / Bearing characteristics / Offshore wind power / Silty soil / Chalky soil

References

[1] Cai Z, Wang Q, Guan Y, Han X, Li W. Influences of bulkheads on bearing characteristics of composite bucket foundation of offshore wind turbines. Chinese Journal of Geotechnical Engineering, 2021, 43(4): 751-759(in Chinese)

[2] Chen L, Tian H, Xu M. Seismic response analysis of offshore wind power composite bucket foundation based on geotechnical test. Structural Engineers, 2023, 39(6): 171-178(in Chinese)

[3] Cui X, Shi Y, Wei X, Le C, Jiang M, Zhang P. Analysis of bearing characteristics of four-bucket jacket foundation in combined loading mode. Acta Energiae Solaris Sinica, 2024, 45(6): 581-588(in Chinese)

[4] Ding H, Zhang C, Zhang P, Zhai H. Effect of overlying soft soil layer on bearing capacity of four bucket foundation for offshore wind turbines. Journal of Harbin Engineering University, 2020, 41(1): 67-75(in Chinese)

[5] Ebrahimipour A, Eslami A. Analytical study of piles behavior for marine challenging substructures. Ocean Engineering, 2024, 292: 116514

[6] Giddings J, Bloomfield H, James R, Blair M. The impact of future UK offshore wind farm distribution and climate change on generation performance and variability. Environmental Research Letters, 2024, 19(6): 064022

[7] ISO. ISO 19905-1-2023. Petroleum and natural gas industries-Site-specific assessment of mobile offshore units-Part 9: Foundations, 2023, Geneva, International Organization for Standardization

[8] Jia N. Analysis on penetrating-levelling mechanism and penetration resistance of bucket foundation with inner compartments for offshore wind turbines, 2017, Tianjin, Tianjin University4-8(in Chinese)

[9] Le C, Ding H, Zhang P. Influences of bulkheads on the bearing mode of concrete bucket foundation for offshore wind turbine. Engineering Mechanics, 2013, 39(212-19(in Chinese)

[10] Le C, Ren J, Jiang M, Zhang P, Ding H. Analysis of the moment bearing capacity of four-bucket jacket foundation in sandy soil. Ocean Engineering, 2021, 39(2): 12-19(in Chinese)

[11] Liu J, Ni D, Xiao J, Zhang P. Analysis of penetrating process of single-column composite bucket foundation for offshore wind turbine. Acta Energiae Solaris Sinica, 2023, 44(3): 239-243(in Chinese)

[12] Liu Y, Ding H, Zhang P. Model tests on bearing capacity of composite bucket foundation in clay. Chinese Journal of Geotechnical Engineering, 2016, 38(12): 2315-2321(in Chinese)

[13] Mahmood MR, Fattah MY, Khalaf A. Experimental investigation on the bearing capacity of skirted foundations on submerged gypseous soil. Marine Georesources & Geotechnology, 2020, 38(10): 1151-1162

[14] Mosallanezhad M, Hataf N, Ghahramani A. Experimental study of bearing capacity of granular soils, reinforced with innovative Grid-Anchor system. Geotechnical and Geological Engineering, 2008, 26(3): 299-312

[15] NEA. Design code for offshore wind farm turbine foundations, 2018, Beijing, China Water & Power PressNB/T 10105-2018. (in Chinese)

[16] Rezazadeh S, Eslami A. Skirted semi-deep foundations behavior on deposits with variable undrained shear strength. Ships and Offshore Structures, 2020, 15(5): 492-502

[17] Soares-Ramos EPP, Oliveira-Assis L, Sarrias-Mena R, Fernández-Ramirez LM. Current status and future trends of offshore wind power in Europe. Energy, 2020, 202: 117787

[18] Zhang P, Feng J, Shi Y, Le C, Ding H. Influence of length to diameter ratio of the skirt on horizontal bearing characteristics of tripod suction jacket foundation in sandy soil. Journal of Marine Science and Application, 2024, 23(2): 406-416 in Chinese)

[19] Zhang P, Guo W. Load-bearing characteristics of offshore wind power single column composite bucket foundation under composite loading conditions. Advances in New and Renewable Energy, 2024, 12(2124-132(in Chinese)

[20] Zhang P, Qi X, Zhang C, Le C, Ding H. Penetration tests of multi-bucket foundation in sand for offshore wind turbines. Journal of Ocean University of China, 2023, 22(4): 949-960 in Chinese)

[21] Zhang P, Wang Y, Xiao J, Gao Y. Investigation into the towing performance of single-column composite bucket foundations. Hydro-Science and Engineering, 2024, 2024(3): 99-107(in Chinese)

[22] Zhang P, Wei Y, Xiao J, Ding H, Li Y. Torsional bearing capacity of composite bucket foundation in silty sand. Acta Energiae Solaris Sinica, 2021, 42(9): 270-278(in Chinese)

[23] Zhang Q, Zhang P. Effect of combined action of scouring and earthquake on the displacement deformation of single-column composite bucket foundation. Advances in New and Renewable Energy, 2023, 11(6): 548-555(in Chinese)

RIGHTS & PERMISSIONS

Harbin Engineering University and Springer-Verlag GmbH Germany, part of Springer Nature