Experimental study of the seabed responses induced by a floating column with a heave plate

Abstract

Oscillatory flows induced by the heave motion of floating platforms can alter seabed pore pressure gradients and flow shear stresses, potentially triggering sediment transport and scour. In this study, laboratory experiments are conducted in a large wave flume to investigate the seabed response around a floating column. During the experiments, vertical displacement of the column, free surface elevation, dynamic pore pressure, and final bed morphology are measured and analyzed. Results show that the heave period dominates the frequency response of both free-surface waves and pore pressure, whereas amplitude governs the near-field energy intensity. A distinct radial zoning mechanism is identified: vortex-induced shear stresses coupled with destabilizing seepage forces lead to the annular trench formation at the periphery, while vertical pressure gradients prevail at the center. Notably, short-period high-frequency oscillations significantly restrict the radial extent of sediment transport, leading to bowl-shaped undercutting rather than broad scour. These findings provide some engineering guidance for floating wind farm placing, spacing, and scour protection.