HCA 4 PInS: Development of a method for realistic simulation of pile installation using an HCA model

• Applicants: Dr.-Ing. Jan Machacek; Professor Dr.-Ing. Patrick Staubach; Professor Dr.-Ing. Torsten Wichtmann; Professor Dr.-Ing. Hauke Zachert
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 526401246

As part of the "Klimaschutzprogramm 2030", the installed capacity of offshore wind turbines shall be increased to 25 GW by 2030. In addition to the development of new wind farms, this will be achieved by the planned market entry of wind turbines with a capacity of up to 14 MW. However, the foundations for these turbines must be installed under strict environmental and nature conservation conditions. The conventional pile installation method of impact driving can only meet these requirements if additional technical solutions are used to reduce pile driving noise. An alternative installation method is the comparatively low-emission vibratory pile driving. However, initial model and field tests show that the load-bearing capacity of vibrated piles is lower compared to the one of driven piles. Common design procedures using nonlinear springs (p-y curves) or the finite element method (FEM) neglect the actual installation process. The aim of this project is to develop a suitable numerical strategy based on the so-called "zipper-method" in combination with a high cycle accumulation (HCA) model, which allows a realistic simulation of the installation process and the subsequent computation of the (high) cyclic lateral loading from wind and wave action. Herein, the pile installation simulation will, for the first time, take into account the most important parameters of the installation, while the pile-soil interaction will be represented as accurately as possible. This includes, for example, the mapping of the actual installation time and frequency or the actual number of load cycles, effects of inertia, and partial drainage. The developed numerical method is validated using model and field tests from the literature. Based on this numerical strategy, analytical approaches are derived that allow a simplified consideration of the installation effects depending on, among others, the installation method, the soil density and the drainage conditions in common wished-in-place FEM calculations. This will ensure the knowledge transfer from this research project into engineering practice, and enable planning engineers and authorities to consider the influence of pile installation in the pre-dimensioning and detailed design of monopile foundations. Furthermore, the numerical tools developed in this project allow a systematic investigation of pile installation effects and can thus support the development and evaluation of novel installation methods.

• DFG Programme: Research Grants