Sensitivity analysis of scour parameters of offshore pile foundation considering seabed characteristics and countermeasures for passive scour protection

Abstract

Offshore wind turbine pile foundations are subject to various degrees of scour under the combined action of waves and currents, which reduces the pile-soil contact depth and threatens the structural safety of wind turbines. Existing standards primarily specify hydrodynamic and structural parameters of wind turbine foundations but lack detailed classifications of seabed types. Field investigations indicate that seabeds composed of very fine sand and silt with varying relative densities and permeabilities exhibit significantly different scour depths.To achieve high-accuracy scour depth prediction, this study conducts scour tests on pile foundations across different seabed types and employs neural network models to analyze the scour evolution in seabeds with distinct characteristics. Sensitivity analyses are performed on three main categories of parameters influencing pile scour: hydrodynamic parameters, pile foundation parameters, and seabed geotechnical parameters.Test result and sensitivity analyses reveal that within the seabed geotechnical parameters, the internal permeability of seabed sediments is the most critical factor affecting scour development. The underlying mechanism is that seabeds with low permeability coefficients fail to form sufficient internal fluid pathways, resulting in reduced external fluid drag and less sediment mobilization, which ultimately leads to shallower scour depths.Based on these findings, three passive protection countermeasures aimed at reducing seabed permeability are proposed, providing valuable references for scour prediction and passive protection strategies for offshore pile foundations under complex marine conditions.

Keywords

pile scour / offshore wind power / seabed characteristics / scour prediction / scour protection / sensitivity analysis