A master thesis from Aalborg University
Geotechnical Design of Embedded Mooring Systems: Analysis of Chain-Soil Interactions’ Effect on Suction Anchor Design
[Geotechnical Design of Embedded Mooring Systems]
Term
4. term
Education
Publication year
2023
Submitted on
2023-06-09
Pages
151 pages
Abstract
This thesis investigates the geotechnical design of suction anchors and embedded mooring chains for floating wind turbines. The study addresses three questions regarding the embedded chain-soil interactions, the modelling of the pull-out capacity of suction anchors, and the optimisation of the combined mooring system. Regarding embedded chain-soil interactions, three approaches, Neubecker and Randolph [1995], Lee et al. [2014], and Mortensen [2015] were evaluated. Mortensen’s method gave reasonable results in estimating chain configuration, load reduction, and the increase in loading angle. A series of FEA using PLAXIS 3D considered several aspects of modelling the pull-out capacity for different load configurations. The analyses concluded that the self-weight of the anchor should be modelled as this influences the displacement field. Furthermore, applying force-controlled loading provided reasonable results in contrast to displacement-controlled loading. The optimisation employed a surrogate-based approach, incorporating Mortensen’s chain-soil interaction model and FEA. The optimisation minimised material consumption, revealing that increasing the skirt length is more beneficial than increasing the diameter. The padeye position of an optimised anchor was found to be 0-0.25 times the skirt length. The findings offer guidance for engineers in the optimisation of anchor design, considering the interaction effects with mooring chains. Implementing these insights can enhance overall load-bearing capacity, reliability, and cost-effective solutions for the entire mooring system of floating wind turbines.
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