无封装FBG应变传感器在桩基试验中的标定研究

Experimental study on the calibration of unencapsulated FBG strain sensors in pile foundation test

针对海上风电桩基的沉桩模型试验,采用无封装分布式光纤光栅(Fiber Bragg Grating,FBG)应变传感器对模型桩的沉桩过程进行应变监测,为提高FBG应变传感器的测量精度,通过采用自主设计并研制出的标定装置,提出了一种用于桩基试验的无封装FBG应变传感器灵敏度系数的标定方法,并将标定结果与理论值进行对比。随后,在模型桩的桩顶、桩中和桩底位置安装电阻式应变片进行加载试验,将FBG应变传感器的测量应变数据与电阻应变片测量数据进行对比分析。研究结果表明:标定后的FBG应变传感器的灵敏度系数与理论值相比存在较大差异,最大误差为6.76%,这是由于标定后的FBG应变传感器测量结果更为准确,并且FBG传感器的测量精度要高于应变片。该标定试验为后续沉桩试验模型桩应变、应力及桩侧阻力的监测提供了可靠的数据支撑。

For the driving model test of offshore wind power pile foundation,Fiber Bragg Grating(FBG)strain sensor is used to monitor the strain during the driving process of the model pile.In order to improve the measurement accuracy of FBG strain transducers,a cali-bration method for the sensitivity coefficient of unencapsulated FBG strain transducers for pile foundation testing is proposed by using self-designed and developed calibration devices,and the calibration results are compared with the theoretical values.Subsequently,re-sistive strain gauges are installed at the top,middle and bottom positions of the model piles for loading tests,and the strain data meas-ured by the FBG strain transducers are compared and analyzed with the resistive strain gauge measurement data.The results show that the sensitivity coefficient of the calibrated FBG strain sensor differs significantly from the theoretical value,with a maximum error of 6.76%,and that the measurement results of the calibrated FBG strain sensor are more accurate,and the measurement accuracy of the FBG sensor is higher than that of the strain gauge.The calibration test provides reliable data support for the monitoring of strain,stress and pile lateral resistance of the model pile for subsequent pile driving tests.