成层土中考虑桩侧土竖向作用的螺纹桩动力响应

Dynamic response of screw pile considering vertical action of pile side soil in layered soil

摘要:

螺纹桩与桩侧土的作用相对复杂,为研究竖向荷载作用下螺纹桩的振动特性,从桩侧土的三维波动出发,考虑土体的成层特性和桩侧土的竖向作用,对滞回阻尼地基中螺纹桩纵向振动特性进行研究。基于三维波动理论建立桩侧土波动方程,采用Laplace变换和修正阻抗函数传递法得到桩土完全耦合条件下的螺纹桩振动响应解。将理论计算结果与现场实测曲线进行对比,证明螺纹桩-土相互作用模型的合理性。结果表明:相比桩侧土为均质体的假定,考虑土体的成层特性可以充分考虑应力波在分层界面的反射和折射现象,更符合实际情况；在有效桩长范围内,随着桩长的增加,桩侧土对螺纹桩的侧摩阻力越大,阻尼效应越明显;螺纹桩螺牙的存在对桩体具有一定的减振效应,且随着螺牙外径的增加,桩顶复刚度曲线的振幅水平和共振频率均显著减小。理论模型能较好地模拟螺纹桩与成层土的相互作用机理,为螺纹桩的应用提供理论支撑。

Abstract:

The effect of screw pile and pile side soil is relatively complex. In order to study the vibration characteristics of screw pile under vertical load, the longitudinal vibration characteristics of screw pile in hysteretic damping foundation are studied from the three-dimensional fluctuation of pile side soil, considering the layered characteristics of soil and the vertical action of pile side soil. Based on the three-dimensional wave theory, the wave equation of pile side soil is established, and the vibration response solution of screw pile under the condition of complete coupling between pile and soil is obtained by Laplace transform and modified impedance function transfer method. The theoretical calculation results are compared with the field measured curves to prove the rationality of the screw pile-soil interaction model. The results show that compared with the assumption that the soil around the pile is homogeneous, considering the layered characteristics of the soil can fully consider the reflection and refraction of the stress wave at the layered interface, which is more in line with the actual situation. In the range of effective pile length, with the increase of pile length, the side friction resistance of pile side soil to screw pile is larger, and the damping effect is more obvious. The existence of the screw thread of the screw pile has a certain vibration reduction effect on the pile body, and with the increase of the outer diameter of the screw teeth, the amplitude level and resonance frequency of the complex stiffness curve of the pile top decrease significantly. The theoretical model can better simulate the interaction mechanism between the screw pile and the layered soil, and provide theoretical support for the application of the screw pile.