黏弹性土层中单桩纵向振动的对比分析

Comparison and Analysis of the Longitudinal Vibration of the Single Pile in Viscoelastic Soil Layer

在频率域内研究了黏弹性土层中端承桩纵向振动的动力特性.将土骨架视为具有分数阶导数本构关系的黏弹性体,基于黏弹性理论,采用平面应变模型给出了分数阶导数黏弹性土层的动力阻抗.考虑桩纵向振动时的横向惯性效应,将桩等效为Rayleigh-Love杆,得到了桩头动力复刚度和导纳的解析表达式.通过数值计算,分析了不同模型土条件下桩头动刚度因子和阻尼随激励频率的动力响应.同时,研究了Rayleigh-Love和Euler-Bernoulli两种模型桩动力特性的差异.分析了桩-土界面连续性模型和相对滑移模型对黏弹性土层中桩纵向振动的影响.结果表明:1随着阶数和材料参数比的增加,桩头刚度因子和阻尼明显减小;2对于大直径桩,随着外荷载激励频率的增加,桩横向效应对刚度因子和阻尼有显著影响.3连续性模型条件下桩头的刚度因子和阻尼在共振时的振幅小于相对滑移模型条件.

Dynamic characteristics of longitudinal vibration of the end-bearing pile in viscoelastic soil layer were studied in frequency domain. The soil skeleton was treated as a viscoelastic medium with fractional derivative constitutive relations. Based on viscoelastic theory, the dynamic impedance of fractional derivative viscoelastic soil layer was obtained by the plane strain model. Taking effect of the transversal deformation and inertia of the pile into account and modeling pile as a Rayleigh-Love rod, the analytical expressions for dynamic stiffness and admittance of the pile top were obtained. By the numerical method, the dynamic responses of dynamic stiffness factor and damping of pile top against the frequency for different modeling soil were analyzed. The difference for dynamic characteristics of pile with the two modes of Rayleigh-Love and Euler-Bemoulli was studied. The influences of the continuity model and the relative slip model at the interface between pile and soil on the longitudinal vibration of pile in viscoelastic soil layer were analyzed. It is shown that the stiffness and damping of the pile top are significantly reduced against the order and material parameters increasing. For large diameter pile, the influence of transversal effects on the stiffness factor and damping is much great for the pile when the exciting frequency is large. The amplitudes of the stiffness and damping of the pile top at resonance for continuity model is much smaller than ones for the relative slip model.