Experimental Study on Tilt Adjustment Technique of Tripod Bucket Jacket Foundation for Offshore Wind Turbine in Sand

Abstract

For the tripod bucket jacket foundations used in offshore wind turbines, the probable critical tilt angles should be avoided during tilt adjustment operation. Thus, these critical values must be identified by engineers, and remedial techniques must be established prior to the occurrence of the problem. Model tests were carried out for typical tilting conditions of tripod bucket foundations, which were allowed to tilt freely at various penetration depths without interruption by manual operation. After the foundation ceased its tilting, some measures, such as water pumping, water injection, air injection, or a combination of the above methods, were enabled for adjustment. The research results showed two critical values in the tilting state of the tripod bucket jacket foundation, namely the terminal and allowable angles. In the installation condition, the terminal angle was negatively correlated with the initial penetration depth, but the opposite was observed with the removal condition. The allowable angle was less than or equal to the terminal angle. The allowable angle in the installation was related to the terminal angle. The critical angles all varied linearly with the initial penetration depth. When tilting during installation, adjustment measures can be used in the order of high drum pumping, low drum water injection, high drum pumping and low drum water injection, air injection, and exhaust. When tilting during removal, the sequential use of low drum water injection, air, and exhaust was applied. For buckets that were sensitive to angle changes, adjustment measures of the “point injection” mode can be selected.

Keywords

Tripod bucket jacket foundation / Tilt adjustment / Penetration and removal / Terminal angle / Allowable angle / Offshore wind turbine

References

[1] Achmus M, Schroeder C. Installation and bearing behaviour of bucket foundations for offshore structures. Bautechnik, 2014, 91(9): 597-608

[2] Chen Q, Zhang P, Ding H, Le C, Xu Y. Study on Seepage Characteristics of Composite Bucket Foundation Under Eccentric Load. China Ocean Engineering, 2021, 35(1): 123-134

[3] CNS (2019) Standard for geotechnical testing method GB/T 50123-2019 (in Chinese)

[4] Ding HY, Wang LG, Du J. The model tests for adjustment of penetration of multi-bucket foundation platform. Rock and Soil Mechanics, 2004, 25(3): 386-390

[5] DNV (2005) Geotechnical Design and Installation of Suction Anchors in Clay Recommended Practice DNV-RP-E303

[6] Jia N (2018) Analysis on Penetration-levelling Mechanism and Penetration Resistance of Bucket Foundation with Inner Compartments for Offshore Wind Turbines. Tianjin University.

[7] Jia N, Zhang P, Liu Y, Ding H. Bearing capacity of composite bucket foundations for offshore wind turbines in silty sand. Ocean Engineering, 2018, 151: 1-11

[8] Ren Y, Vengatesan V, Shi W. Dynamic Analysis of a Multi-column TLP Floating Offshore Wind Turbine with Tendon Failure Scenarios. Ocean Engineering, 2022, 245: 110472

[9] Wang X, Zeng X, Li J. Vertical performance of suction bucket foundation for offshore wind turbines in sand. Ocean Engineering, 2019, 180(4): 40-48

[10] Wu Y, Zhang Y, Li D. Solution to critical suction pressure of penetrating suction caissons into clay using limit analysis. Applied Ocean Research, 2020, 101: 102264

[11] Zhang C (2018) Research on Penetration and Sinking-leveling of Multi Bucket Foundation for Offshore Wind Turbines. Tianjin University.

[12] Zhang PY, Ding HY, Le CH. Model tests on tilt adjustment techniques for a mooring dolphin platform with three suction caisson foundations in clay. Ocean Engineering, 2013, 73: 96-105

[13] Zhang PY, Ding HY, Le CH. Installation and removal records of field trials for two mooring dolphin platforms with three suction caissons. Journal of waterway, port, coastal, and ocean engineering, 2013, 139(6): 502-517

[14] Zhang PY, Ding HY, Le CH. Penetration and Removal of the Mooring Dolphin Platform with Three Caisson Foundations. Journal of Offshore Mechanics and Arctic Engineering, 2013, 135(4): 041302

[15] Zhang PY, Zhang Z, Liu YG, Ding HY (2016) Experimental study on installation of composite bucket foundations for offshore wind turbines in silty sand. Journal of Offshore Mechanics and Arctic Engineering 138(6). https://doi.org/10.1115/L4034456

[16] Zhang Y, Shi W, Li DS, Li X. A novel framework for modeling floating offshore wind turbine with consideration of the dynamic effects of mooring system based on the vector form intrinsic finite element (VFIFE) method. Ocean Engineering, 2022, 262: 112221