A centrifuge study on the dimensionless factor for drainage around large-diameter offshore monopiles
A centrifuge study on the dimensionless factor for drainage around large-diameter offshore monopiles
Offshore monopile foundations are increasing in size, to support ever-bigger wind turbines. Current monopile diameters are of the order of 10 m, with further increases planned. The assumption of a fully drained cyclic response for sand around monopiles, while sufficiently accurate for the small diameters used in the past, becomes unreliable for the large diameters used today (>10 m), as the longer drainage path around the monopiles circumference decreases the sands capacity to fully drain within a load cycle. Designing such systems while accounting for partial drainage effects is the subject of ongoing research. An essential step in design will be the classification of the expected level of drainage, based on the properties of the monopile and the surrounding soil. In this work, a proposed dimensionless factor for drainage around large-diameter monopiles is examined using centrifuge experiments, performed at the beam centrifuge of ETH Zurich as part of the GEOLAB project. The proposed factor depends on the soils bulk stiffness and hydraulic conductivity, and on the piles dimensions. The results from three tests where the monopile was subjected to displacement-controlled loading are presented. Each test achieved the same value for the drainage factor through a different combination of loading frequency, pile diameter, and viscosity-adjusted hydraulic conductivity. The drainage response as represented by excess pore water pressures at homologous points of the different models is shown to be remarkably consistent across experiments, verifying the validity of the proposed dimensionless factor.
Rory Fleminger; O. Adamidis; Christopher Martin; Athanasios Agalianos; Liam Jones; I. Anastasopoulos; Proserpine Peralta; Nicole Santos
11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)
Session 2: Scaling laws and fundamentals
https://doi.org/10.53243/ICPMG2026-398