部分埋入群桩的竖向振动特性

采用动力Winkler动力梁模型,由传递矩阵法推导了部分埋入单桩竖向振动的计算公式;充分考虑了被动桩与土体的共同作用,基于桩–桩相互作用因子的叠加法,建立了部分埋入群桩的动力模型。通过参数(埋入比L1/L2、桩间距s/d和激振频率f)探讨,得到了匀质半空间和层状地基中常见部分埋入群桩的动力特性变化规律:①埋入比的增大会显著的降低单桩和群桩的阻抗;②部分埋入桩的存在会降低桩–桩相互作用,从而进一步消弱群桩的空间协同工作的能力;③部分埋入桩对于群桩基础的低频动力响应影响不大,但随着频率的提高而日益显著。然后,本文的退化解与现场实测结果和试验数据进行了比较。最后,本方法被用于分析某海上风力发电机组群桩基础的幅频曲线,并指出了其动力响应与完全埋入群桩的差异,为工程设计提供参考。

Vertical vibration of partially embedded pile groups

A simplified analytical method is developed for the axial harmonic response of partially embedded pile groups in homogeneous and non-homogeneous soil deposits.Based on pile-to-pile interaction factors,the transfer matrix method is used to establish the dynamic model of partially embedded pile groups,while the pile is treated as dynamic Winkler beam.A comprehensive parameter study focuses on the influence of length ratio(L1/ L2),pile spacing(s/d) and vibration frequency(f) on the dynamic response of pile groups,and the following conclusions can be drawn:① the increase of length ratio(L1/ L2) will reduce the vertical dynamic impedance of a single pile and pile groups;② the pile-pile interaction factors vary with the pile spacing and vibration frequency,and will be seriously weakened due to the existence of length ratio(L1/ L2);③ the length ratio(L1/ L2) has little influence on the dynamic response of pile foundations in low frequency,but it will be more and more evident with the increase of vibration frequency.And this approach is verified by comparing field test results.Finally,the present model is used to predict the vertical dynamic vibration of a pile foundation of an offshore platform.