基于光纤光栅的双壁开口模型管桩测试技术研究

Research on testing technology of double-walled open pipe pile based on FBG

针对光纤光栅传感器在模型管桩试验应用情况,提出了一种光纤光栅传感器理论灵敏度系数和实验灵敏度系数应变标定方法。结合理论分析,在封装FBG应变传感器前,对模型管桩内、外管进行有限元Abaqus应力分布模拟分析,得到双壁开口模型管桩对封装FBG应变传感器没有影响,提高了实验应变测量精度。对模型管桩封装后的FBG应变传感器进行标定实验,每次按200逐级加载后并卸载,循环加载5次,得到内外管FBG传感器应变灵敏度系数分别为2.15pm/με、2.24pm/με,且线性度均达到0.999以上。该方法简单、易操作,可用于光纤光栅应变传感器在模型管桩试验前的标定,为光纤光栅传感器在试验和工程中应用奠定了基础。

In order to measure the pile friction,pile tip resistance and soil resistance of the open pipe pile during sinking,a double-walled open mode pipe pile with fiber Bragg grating (FBG)sensor is designed. A fiber grating sensor theoretical sensitivity coefficient and experimental sensitivity coefficient strain calibration method is proposed in view of the application of FBG sensors in the model pipe pile test.Combined with the theoretical analysis,the finite element Abaqus stress distribution of the model pipe pile is simulated and analyzed before the FBG strain sensor is encapsulated.The double-walled open model pipe pile has no influence on the FBG strain sensor and the experimental strain measurement accuracy is improved.The calibration experiment of FBG strain sensor after the model pipe pile encapsulation is carried out by every step loading and unloading of 200με,and it is loaded for 5times.The strain sensitivity coefficients of FBG sensor encapsulated on internal and external tubes are 2.15pm/με and 2.24pm/με,respectively,with Iinearity greater than 0.999.At the same time,the method is simple and easy to operate, and is suitable for the calibration of fiber grating strain sensor before the model pipe pile test,which lays the foundation for the application of FBG sensors in the experiment and engineering.