Restrike test on a vibratory and impact driven pile in sand

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The foundation structure accounts for approx. 1/3 of the total costs of offshore wind turbines. Consequently, optimizing its design and installation is one of the industry's goals to reduce project costs. Environmentally friendly installation methods are of particular interest. For that, the use of vibratory driving has been investigated for several years and it has been found that the installation process as well as the pile-soil interaction and disturbance of the surrounding soil after installation are significantly influenced by the operational parameters. These so-called installation effects need to be considered in the design process as they impact the load bearing behaviour. However, there are currently no general prediction approaches available due to a lack of real or large-scale test data. As a result, monopiles are currently only partially installed by vibration in most cases and must be impact-driven afterwards to reach target depth. As part of the German research project Seismic_on_Piles, investigation methods to enable cost-effective monitoring of the subsoil with repeated seismic measurements are developed to derive relationships between seismic data and geotechnical parameters. For this purpose, a large-scale test campaign involving vibratory and impact-driven monopile models is conducted. The innovation are the extensive soil measurements, like CPTs, earth pressure and seismics, carried out from pile installation through testing to their decommissioning. This paper provides a contribution to the understanding of the load bearing behaviour of vibratory-driven monopiles. The experimental campaign is presented below. Preliminary results including restrike tests before the lateral testing phase are analysed.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

6 - Pile Installation Challenges and Decommissioning in sands and clays: monopiles, anchor piles, pin piles