光纤布拉格光栅用于黏质土中静压沉桩贯入特性的测量研究

Measurements of Penetration Characteristics of Jacked Piles in Clayey Soil Based on Fiber Bragg Gratings

为深入研究光纤光栅(FBG)传感技术在静压沉桩贯入特性测试中的适用性,采用大比例模型实验系统进行静压沉桩贯入实验。数据测试采用光纤光栅应变传感器,同时采用轮辐式压力传感器和光纤光栅压力传感器作对比。通过在桩端和桩顶安装全截面动态轮辐压力传感器和光纤光栅压力传感器,对比分析基于两种传感技术的静压沉桩贯入过程差异。同时基于FBG传感技术采集桩身应变数据,研究静压沉桩贯入过程的桩身侧摩阻力、桩身轴力和桩身单位侧摩阻力等贯入特性。研究结果表明:FBG传感技术对静压沉桩的贯入测试性能优越,能够准确体现静压沉桩的贯入特性,清晰反映随沉桩深度增加的静压沉桩过程,同时由静压沉桩过程分析发现,桩顶压桩力、桩端阻力、桩身轴力和桩身单位侧摩阻力具有稳态贯入的特点,这对静压沉桩的模型实验与工程设计具有较大的参考价值。

To extensively study the applicability of Fiber Bragg grating(FBGs) sensing technology in the penetration test of jacked piles, a large-scale model test system is used to conduct the penetration test of jacked piles. This paper uses a fiber grating strain sensor for data testing, while using a spoke type pressure sensor and a fiber grating pressure sensor as control groups. By installing a full-section dynamic spoke pressure sensor and a fiber grating pressure sensor at the end and top of the pile, respectively, the difference between the penetration processes of the jacked piles based on the two sensing technologies is compared and analyzed. Simultaneously, the pile body strain data is collected based on the FBG sensing technology, and the penetration characteristics of the side frictional resistance, the axial force, and the unit side frictional resistance of the pile are studied. Results show that the FBG sensing technology has superior performance in the penetration test of static pressure piles, can accurately reflect the penetration characteristics of jacked piles, and can clearly reflect the pile jacking-in process with the increase of pile driving length. Furthermore, it is found that the driving pressure, the end resistance, the axial force, and the unit side frictional resistance of the pile body have the characteristics of a steady-state penetration. Therefore, this study presents a great reference for the model test and the engineering design of static pressure piles.