The Remedial Performance of Suction Caisson Foundations for Offshore Wind Turbines under Seismically Induced Liquefaction in the Seabed: Shake Table Testing

The assessment of liquefaction hazards to offshore wind turbines (OWTs) requires an improved understanding of the interplay among the foundation geometry, ground shaking, and liquefaction-induced deformations. In this note, shaking table model tests were used to evaluate the behavior of suction caissons due to seabed liquefaction. Spectral accelerations and settlement of OWT foundations of varying skirt lengths on liquefiable sand were analyzed and compared.

Insights into the performance of caisson skirts as a liquefaction countermeasure relative to the benchmark models are provided. The experimental results identified the two controversial mechanisms controlling shear-induced caisson settlement; the liquefaction-induced bearing capacity failure as the skirt length increases, whereas the larger net excess pore-water pressures within skirts contribute more significantly to reducing seismic demand.

Overall, the skirted foundation with the longest skirt length experienced the least settlement and acceleration, which may be ascribed to the interplay of various mechanisms, i.e., the confining effect of the skirt and a slower pore-water pressure dissipation that limits the possibility of drainage.