For the design of large-diameter monopile foundations for offshore wind turbines, proper assessment of the soil degradation due to the effects of cyclic loading is vital to ensure a safe and optimized foundation design. However, the assessment of soil degradation under cyclic loading and its effect on the foundation design under different load scenarios is a complex issue. Available methodologies for these assessments are either too simplified incorporating several assumptions and approximations, or they are very complex and highly computationally demanding (so that they cannot be implemented in the modern iterative design processes of new/future offshore foundations). Such a problem has led to an inaccurate and conservative design, which means higher costs for offshore wind energy.
In the main guidelines of the offshore geotechnical designs (DNVGL-ST-0126, DNVGL-RP-C212, API-RP-2A-WSD, and API-RP-2GEO), no clear method is provided that can be applied for large diameter piles for the assessment of cyclic soil-structure-interaction for coarse-grained materials. Therefore, the applied methodologies in nowadays designs are not concrete and robust and are sometimes very subjective.
The purpose of the research is to develop a practical and accurate approach for determining the cyclic degradation of soil around monopile foundations. The method will be developed for coarse-grained materials, will be representative of both one-way and two-way loading conditions, and will be developed to be representative of the XL monopile foundations. This will enhance a more cost-efficient and safe geotechnical design of XL monopile foundations for offshore wind turbines and hence provide significant value for a reduction in CO₂-emissions.
The work will incorporate 3D Finite Element (FE) modeling to properly consider the effects of drainage and to consider the varying soil stresses with depth, distance to the pile, and orientation compared to the loading direction. Based on a series of large-scale experiments and a comprehensive parametric study with several 3D FE models, regression analysis will be performed to establish a practical expression for the evaluation of cyclic degradation. Such practical expression will allow for incorporation with modern iterative design processes of new/future offshore foundations.


Simplied framework for predicting the cyclic degradation for extra-large diameter monopiles installed in coarse grained material.
Effektiv start/slut dato01/08/202231/07/2025


  • University of Bremen


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