黏土中海上风电超大型吸力桩基础沉贯安装分析

Installation Analysis of Super Large Suction Pile Foundation for Offshore Wind Power in Clay

吸力桩基础安装前需要进行沉贯和结构屈曲分析。针对国内首个全场采用吸力式基础的大型风电场,提出一种在黏土中超大型吸力桩沉贯阻力改进计算方法,在现有规范基础上,考虑桩侧向土的扰动效应,引入黏性土灵敏度,对桩侧土阻力进行折减。基于安装海域实测海床土壤参数,对吸力桩导管架基础沉贯阻力及所需压差进行计算,通过与DNVGL规范和实测值对比,验证改进计算方法的准确性,基于此方法对安装时可能需要临时顶起的阻力进行分析;进一步使用有限元法对两种吸力桩顶盖进行数值建模,开展吸力桩在安装沉贯及临时顶起过程顶盖屈曲特性研究。结果表明:随着贯入深度的增加,吸力桩导管架基础的沉贯阻力逐渐增大,DNVGL规范计算得出的沉贯阻力与所需压差较大,而改进方法计算结果与实测值更为接近;DNVGL规范计算得出的顶起所需压差整体上明显大于改进方法计算值;吸力桩在达到沉贯以及顶起所需最大压差时,顶盖处于弹性阶段,不会发生屈曲破坏。

Before the installation of suction pile foundation,the penetration and structural buckling analysis are required.This paper proposes an improved calculation method for penetration resistance of super large suction pile in clay for the first large-scale wind farm in China that adopts suction type foundation in the whole site.On the basis of existing specifications,considering the disturbance effect of soil on the side of pile,the sensitivity of cohesive soil is introduced to reduce the soil resistance on the side of pile.Based on the measured seabed soil parameters in the installation sea area,the penetration resistance and required differential pressure of suction pile jacket foundation are calculated.The accuracy of the improved calculation method is verified by comparing with DNVGL specification and measured values.Based on this method,the resistance that may require temporary jacking during installation is analyzed.Further,the finite element method is used to conduct numerical modeling for the two kinds of suction pile caps,and the buckling characteristics of caps during the installation,penetration and temporary jacking of suction piles are studied.The results show that,(a)with the increase of penetration depth,the penetration resistance of suction pile jacket foundation gradually increases,the penetration resistance calculated by DNVGL code and the required pressure difference are larger,and the calculation results of the improved method are closer to the measured values;(b)the differential pressure required for jacking calculated by DNVGL specification is obviously greater than that calculated by the improved method on the whole;and(c)when the suction pile reaches the maximum differential pressure required for penetration and jacking,the top cover is in an elastic stage,and the buckling failure will not occur.