考虑海床特性的海上桩基冲刷参数敏感性分析及被动冲刷防护对策

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

摘要

海上风电桩基基础在波流作用下，均会产生不同程度的冲刷，导致桩土接触深度减少，影响风机安全。现行规范围绕水动力及风机基础结构参数进行了限定与说明，但对不同类型的海床并未进行详细划分。实地观测表明，海底可能存在不同相对密度及渗透性的极细砂和粉砂，表现出差异明显的冲刷深度。因此，为实现高精度冲刷深度预测，开展了不同海床类型下的桩基冲刷试验，并结合神经网络方法，针对不同特性的海床进行了冲刷发展的研究，并对水动力参数、桩基参数及海床岩土体三大类参数，进行桩基冲刷参数敏感性分析。根据试验结果及参数敏感性分析可知，在海床岩土体参数中，海床沉积物内部渗透性是影响桩基冲刷发展的第一影响参数，其内在原因为：低渗透系数的海床内部无法形成足够的流体通道，外部流体对其拖曳能力低，导致海床泥沙起动量少进而表现为冲刷深度低。并根据此，提出了三种降低海床渗透性的被动冲刷防护治理对策，为海上复杂工况下桩基冲刷预测方法及被动防护治理提供了重要参考依据。

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.

关键词

桩基冲刷 / 海上风电 / 海床特性 / 冲刷预测 / 冲刷防护 / 敏感性分析

Key words

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

Author summay

张平(1985—), 男, 高级工程师, 副主任工程师, 硕士, 主要从事水工结构、海工结构研究。E-mail: [e-mail]

基金资助

山东电力工程咨询院有限公司技术服务项目(37-2024-21-K0001)