Pile sway calculation procedure and control during skirt pile driving operation in the North Sea

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4. Pile sway calculation procedure and control during skirt pile driving operation in the North Sea

ABSTRACT:  This paper discusses the installation difficulties associated with driving long, slender piles that have minimal self-weight penetration.  The most critical issue arises when pile sway occurs during installation, especially when driving begins with the heavy hammer positioned above or within the splash zone. Pile driving operations were performed to support a four-legged steel jacket in water depth of approximately 80m, consisting of four vertical skirt piles with a diameter of 2743mm (108") and 75.0m penetration. The total length of a single pile is 93.5m including stickup portion above mudline and the wall thickness varies between 75mm to 100mm. A submersible hydraulic hammer, IHC S2300, was used for the installation of the piles.

Pile sway occurs when the structural system comprising the pile and hammer or just the pile is exposed to a sea state with a given significant wave height and peak period. The assessment of pile sway to determine the dynamic response is performed through a spectral analysis. A set of sea states is exposed on the pile and hammer assembly. For each sea state and for different pile penetration depths, the most probable expected response is evaluated. The most probable extreme response typically occurs when the hammer is just above the still water level, i.e., predominantly in the splash zone. Experience from this installation demonstrates that the detailed pile sway analysis was an invaluable tool for monitoring and executing the pile installation that took place under a challenging weather condition.

Keywords: Pile sway; Offshore pile; Long pile; Wave loading.

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

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