Pile penetration into scour protection with DEM model

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The long-term performance of offshore foundations frequently relies on the protection against scour. To avoid erosion of the seabed, a coarse granular crushed rock layer is placed around the foundation. This layer is frequently set over the seabed before the foundation is installed, to optimise the construction of the offshore windfarm. In the case of monopiles, suction caissons, or anchors, the rock cobbles forming the scour protection layer may have a significant size and could be at the origin of initial damages and permanent deformations of the steel wall at the base, potentially affecting the continuation and completion of the installation to target depth. Additionally, the scour protection could initially bear the pile self-weight even in case of relatively soft seabeds, which exposes the pile to free falling once the driving installation is started. For the above cases, numerical analyses carried out with the Finite Element Method (FEM) based on continuous material model fail to capture some of the essential features of the problem, that is the interaction between the pile steel wall and the coarse granular hard rock cobbles. The Discrete Element Method (DEM) modelling carried out by the Authors provides a reliable estimate of such interaction, also taking into account a calibrated modelling of the seabed sands within the same DEM, which allow for truly large displacements to be taken into account in the analyses. Comparison with a field measure of a real pile do reinforce the reliability of the predictions obtained by the modelling technique.

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

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