The challenges of follower retrieval after anchor pile installation - a case study
The challenges of follower retrieval after anchor pile installation - a case study
Anchor piles are widely used for mooring structures to the seabed and are also considered a viable solution for anchoring floating wind farms in deeper waters. Anchor piles need to be installed with the pile top at or below seafloor level, requiring a follower between the hammer and the pile to avoid embedment of the hammer in the soil. Plug heave during pile driving and penetration of the soil plug in the follower can make retrieval of the follower a very challenging task, especially when the topsoil layer consists of poorly permeable, cohesive soils. This was the case during the Shell Penguin project, with a stiff glacial till plug making follower retrieval a challenging exercise. In this paper, a detailed analysis of the retrieval process is presented, with analysis of the forces acting on the follower and their relation to the topsoil properties and site conditions. The case study is accompanied by a calculation model, including friction and the occurrence of a (partial) vacuum at the follower-soil interface. The model is generally applicable to assess the required follower retrieval forces of any project, allowing for better installation risk assessment and risk mitigation.
J. van Wijk; Charlotte Stokman; Peter Lachnit
5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)
15 - Mooring lines, Cables, Pipelines, Immersed tunnels and Risers
https://doi.org/10.53243/ISFOG2025-113
Contact Information
- Secretary General - Dr A M McNamara
- Email: [email protected]
- Phone: +44 20 7040 8154
- City, University of London
- Northampton Square
- London EC1V 0HB. United Kingdom