海上风电机组单桩基础模态及参数敏感性分析

Offshore Wind Turbine Monopile Foundation Modal and Parameter Sensitivity Analysis

摘要:

采用里兹向量直接叠加法，在考虑桩土相互作用的条件下对海上风机单桩基础进行模态分析，得到了单桩基础9阶模态特性，基于精确的基础设计，有效地避开了风机叶片工作时的振动频率以及海浪的波动频率.发现前2阶水平向弯曲振型频率为判断单桩基础共振的主要频率.通过探讨套筒、土体、桩基础等方面的一系列参数对单桩风电机组基础模态的影响规律发现单桩基础自振频率随着套筒壁厚、土层水平向参数、桩体壁厚、桩径的增大而增大，随桩悬臂长度的增大而减小，其中受桩径影响最为显著．单桩基础自振频率随桩体埋深呈现非线性变化，并存在临界深度，超过该深度后频率基本保持不变.桩侧土体的摩阻力大小对水平向弯曲振型没有影响．

Abstract:

Modal analysis of offshore wind turbine with monopile foundation based on pile soil interaction is made out by using direct superposition method of Ritz vectors, and then the former 9 order modal characteristics are obtained. With the accurate foundation design, the proximity of fan blade working vibration frequencies and the wave frequency are avoided. The first two orders are horizontal bending vibration modes which are the main frequency in discriminating the resonance frequency of single pile foundation. By probing into the parameters of the sleeve, soil, pile foundation which constitute the single pile foundation, it is found that the vibration frequency rises with the increase of sleeve thickness, soil horizontal parameters, pile thickness and pile diameter while descends with the increase of pile cantilever length. The most sensitive parameter is the pile diameter. The natural frequency of monopile foundation demonstrates nonlinear variation along with the pile length, meanwhile, a critical length is found. The frequency remains invariable if the pile length is beyond the critical value. The friction resistance between pile and soil makes no differences on the bending vibration mode.