基于光纤布拉格光栅传感器的PHC管桩现场静压贯入试验研究

Static-Pressure Penetration Field Test of PHC Pipe Pile Based on Fiber Bragg Grating Sensor

为探究光纤光栅(FBG)传感技术在预应力高强度混凝土管桩(PHC管桩)静压贯入特性现场测试中的适用性及实施温度补偿的必要性,对2根闭口PHC管桩进行了现场静压沉桩试验。将FBG温度传感器、低温敏FBG应变传感器采用刻槽法对称安装于PHC管桩的桩身两侧,通过光纤光栅解调仪对静压过程中的温度变化及桩身应变状态进行监测。试验结果表明,在沉桩过程中桩周土体温度变化高达2.62℃,需采取温度补偿措施,以确保FBG应变传感器测试结果的准确性;试验中24个低温敏FBG应变传感器全部存活,能够对静压过程中的桩端阻力、桩身轴力、侧摩阻力及单位侧摩阻力的变化规律进行动态、实时监测;且此传感器具有温度补偿的功能,能够较好地满足现场试验的测试需求,为FBG传感技术在岩土工程现场测试中的应用提供了新方法。

Herein,two closed prestressed high-strength concrete(PHC)pipe piles were tested under static pressure at the construction field to explore the applicability of fiber Bragg grating(FBG)sensing technology and elucidate the necessity of temperature compensation.FBG temperature sensor and low-temperature-sensitive FBG strain sensor were symmetrically installed on both sides of the PHC pipe pile using the grooving method.The temperature change and strain state of the pile under static pressure were measured using FBG demodulator.The test result indicates that during the process of pile sinking,the temperature variation of the soil around the pile is 2.62℃.Further,the accuracy of the test results of the low-temperature-sensitive FBG strain sensor will be affected if no temperature compensation measures are undertaken.In this test,all low-temperature-sensitive FBG strain sensors survived,facilitating dynamic and real-time monitoring of the change law of pile-tip resistance,pile-axial force,side-friction resistance,and unit-side friction resistance under static pressure.Moreover,the sensor possessed the function of temperature compensation,which can comply with field test requirements,providing a new method for the application of FBG sensing technology in geotechnical engineering field tests.