涌潮荷载下桩式丁坝的动力响应

Dynamic response of pile-groins under the action of bore load

通过势流理论研究了简谐荷载作用下的无黏性流-圆桩-土体系统的动力响应。采用动力Winkler弹性地基梁模型模拟桩与土的相互作用,考虑无黏性流体和桩体的耦合作用,将圆桩散射的特征函数展开,由解析法给出了埋置在土中的圆桩在无黏性流体中的稳态动力响应。最后将实测的钱塘江涌潮冲击荷载用傅立叶变换展开成正余弦荷载。考虑由流体黏性引起的速度力和黏性阻尼的Morison公式的速度力分项,研究分析了涌潮作用下桩式丁坝的受力特性及桩身振动响应。计算结果表明:埋置桩的自振频率较高,而涌潮荷载中高频分量相对较小,所以涌潮下桩式丁坝不易发生共振,工程中可采用静力方法进行设计。

The dynamic response of the water-cylindrical pile-soil system under harmonic load is studied by potential flow theory.The water is assumed as inviscid fluid and the Winkle elastic foundation beam model is applies to simulate the interaction between pile and soil.The coupling between fluid and pile is considered by expanding the eigen-function of the dispersion due to the cylindrical pile.On this basis,the steady dynamic response of the pile inserted in soil under the action of inviscid fluid can be deduced analytically.For verifiying the validity of this analysis result,the in-situ observed impact force acting on a pile due to bore in the Qintang River is expanded into series by means of Fourier transformation to examine the dynamic response of the pile to the velocity force due to fluid viscosity.The velocity force item in Morison formula expressing the viscous damping is taken into account.The calculation result shows that the natural frequency of the pile is high and the high frequency component of the bore load is comparative small,the resonance of pile-groin will not occur.Practically,only the static load should be considered in engineering design.