成层软土地基中锥形桩的横向稳态动力响应分析

Analysis on the lateral steady-state dynamic response of tapered piles in the layered soft soil foundation

摘要

本文基于Timoshenko-Pasternak模型，研究成层软土地基中锥形桩在横向稳态简谐激励作用下的动力响应。将桩身视为线弹性Timoshenko锥形梁-柱，考虑桩侧摩阻力与桩周地基参数沿桩身变化，建立初始轴向压力作用下三参数Pasternak黏弹性地基中锥形桩的动力学模型，推导其横向稳态振动控制微分方程，通过ANSYS命令流构建成层地基中锥形桩的有限元数值模型，求解得到桩身横向位移与内力幅值及固有频率，并与已有模型解对比，以验证模型的合理性。进而探讨相应边界条件下桩身几何参数和桩周地基参数对桩顶横向动阻抗的影响。研究结果表明，在等体积条件下，锥角大小对桩顶横向动阻抗影响较大，在低频范围内增大锥角会有效提高桩顶横向动刚度和动阻尼；桩土刚度比降低时，桩顶横向动阻抗增大，土体剪切效应对桩顶横向动力响应的影响增强；给定桩端约束条件和参数范围内，桩顶横向动刚度和基频大小随着软土厚度的增大而显著降低后趋于平缓。

Abstract

Based on the Timoshenko-Pasternak model, the dynamic response of tapered piles in layered soft soil foundations under lateral steady-state simple harmonic excitation was investigated. The pile body was regarded as a linearly elastic Timoshenko tapered beam-column, and the changes of the lateral friction resistance and the parameters of the pile foundation along the pile body were considered. A dynamic model of tapered piles in the three-parameter Pasternak viscoelastic foundation under the initial axial pressure was established, and the governing differential equation of lateral steady-state vibration was derived. The finite element numerical model of tapered piles in the layered foundation was established using the command flows of ANSYS, and the natural frequency and amplitude of the lateral displacement and the internal force of piles were calculated. The rationality of the model was verified by comparing it with the existing models, and then the influence of the pile body’s geometry parameters and foundation parameters on the lateral dynamic impedance of the pile top was analyzed. The results show that the tapered angle has a great influence on the lateral dynamic impedance of the pile top under the condition of constant volume, and increasing the tapered angle in the low frequency range can effectively improve the lateral dynamic stiffness and dynamic damping of the pile top. When the pile-soil stiffness ratio decreases, the lateral dynamic impedance of the pile top increases, and the influence of the soil shear effect on the lateral dynamic response of the pile top is enhanced. As soft soil thickness augments, the dynamic stiffness and fundamental frequency of the lateral impedance of the pile top exhibit a dramatic decreasing trend, and then tend to level off within the given constraint conditions and parameters.

关键词

成层软土地基 / 锥形桩 / Timoshenko-Pasternak模型 / 有限单元法 / 桩顶横向动阻抗

Key words

layered soft soil foundation / tapered pile / Timoshenko-Pasternak model / finite element method / lateral dynamic impedance of the pile top

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基金资助

安徽工程大学技术开发项目(HX-2024-09-034)