嵌岩桩施工过程中桩端不可避免地会产生一定厚度的沉渣,本文采用虚土桩模型研究其对桩的扭转振动特性的影响。首先,将沉渣看做虚土桩,截面积与桩端一致,并将桩及虚土桩沿竖向划分为若干段;然后,建立扭转动荷载作用下的桩(虚土桩)﹣土体系振动控制方程;通过求解土体振动控制方程,得到桩(虚土桩)﹣土界面环向剪切复刚度;通过求解虚土桩振动控制方程,得到虚土桩顶部的位移阻抗函数(即桩端环向支承复刚度),通过桩段间阻抗函数的递推,求得桩顶位移阻抗函数;最后,将所建立的基于虚土桩模型的解答与已有解答进行对比,并通过参数分析的方法研究不同桩﹣土参数下桩底沉渣厚度、剪切波速及密度对嵌岩桩扭转振动复阻抗的影响。
During the installation of rock-socketed pile, a certain thickness of sediment inevitably accumulates at the pile bottom. Given this, the influence of the pile bottom sediment on the torsional vibration of the rock-socketed pile is investigated with the aid of the virtual soil pile model. First, the bottom sediment is regarded as a virtual soil pile with the same cross-sectional area as the pile tip, and the pile and the virtual soil pile are divided into a series of segments along the vertical direction. Then, the governing equation of torsional vibration of the pile (virtual soil pile) - soil system under torsional dynamic load is established. The circumferential shear complex stiffness at the pile (virtual soil pile)-soil interface is obtained by solving the governing equation of the surrounding soil. The displacement impedance function at the top of the virtual soil pile (i.e., the circumferential complex stiffness at the pile tip) is obtained by solving the governing equation of the virtual soil pile. Furthermore, the displacement impedance function of the pile top is obtained by the recursion of the impedance function at the adjacent pile segments. Finally, the established solution derived based on the virtual soli pile model is compared with the existing solutions. A parameter analysis is conducted to investigate the influence of various factors such as the sediment thickness, shear wave velocity and density on the complex impedance of the rock-socketed pile under different pile-soil parameters.
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