土塞效应对管桩低应变测试视波速的影响研究

Influences of soil plug effect on apparent wave velocity of pipe piles during low-strain integrity

首先,基于附加质量模型建立了考虑环向波动效应的管桩纵向振动频域解析解,然后利用傅里叶逆变换得到半正弦脉冲激振力作用下时域响应半解析解,最后,基于建立的理论模型,研究了土塞效应对管桩视波速的影响,为管桩的低应变无损检测提供更加精确的管桩测试波速计算理论。本文解的理论反演曲线分别与现有理论解的反演曲线、模型试验和现场试验测试曲线进行了比较,验证了本文解的合理性和计算精度。分析表明:土塞效应对管桩视波速的衰减作用随着管桩壁厚和纵波波速的减小而增强;土塞的存在会导致桩端反射信号幅值到达时间随着桩顶接收角度的变化而变化;土塞效应会增大桩端反射信号的宽度。

First,the analytical solution in the frequency domain for the vertical dynamic response of pipe piles is established based on the additional mass model with the consideration of wave propagating both in the vertical and circumferential directions.Then,the corresponding quasi-analytical solution in the time domain for the pipe piles subjected to a vertical semi-sinusoidal impact force is obtained by utilizing the Fourier transform technique.Finally,based on the derived solutions,the influences of soil plug effect on the apparent wave velocity of pipe piles(AWVPP) are investigated.The proposed theory can provide a more precise AWVPP calculation basis for the low-strain integrity tests on pipe piles.The rationality and accuracy of the proposed solution are verified by comparing the fitted curves of the current solution with those based on previous theories and a series of model pipe pile experiments and field tests.The result shows that the reduction degree of AWVPP due to the soil plug effect increases with the decrease in wall thickness and vertical stress wave velocity of the pipe piles.Owing to the soil plug effect,the width of the reflected signal from pipe pile toe is widened,and its arrival time varies as the receiving acceleration transducer moves along the circumferential direction of pipe pile head.