光纤Bragg光栅传感技术在隧道监测中的应用

在阐述光纤Bragg光栅（FBG）传感技术的工作原理和优点的基础上,以昆明白泥井3#隧道为实例,提出FBG传感器在隧道内的铺设方案及温度补偿技术。经过对隧道断面的24h连续监测,讨论隧道内最大温差对Bragg反射中心波长变化的影响,并对隧道每一监测断面上温度传感系统所取得的Bragg波长值进行可靠性的估计,验证FBG监测系统的可靠性。对隧道进行8个月的定期监测,并对隧道断面的应变变化情况进行分析,分析结果表明：干湿季节交替是导致测点应变波动的重要因素,而雨季是致使测点应变变化增大的主要原因。目前隧道二次衬砌结构稳定;同时,研究结果表明,FBG可准确地测出隧道的应变分布,将其应用于隧道变形监测中是可行和有效的。

APPLICATION OF FIBER BRAGG GRATING SENSING TECHNOLOGY TO TUNNEL MONITORING

On the basis of introducing the basic principle and advantages of fiber Bragg grating(FBG)sensing technology,the layout schemes of FBG and temperature compensation technology in the Bainijing Tunnel No.3 in Kunming City are put forward.After 24-hour continuous monitoring,the influence of daylong maximal difference in temperature on the changes of the Bragg wavelength is discussed;and reliability estimation of the Bragg wavelength obtained by temperature sensing system on each monitoring tunnel cross-section is carried out.The calculation results validate the reliability of the FBG measurement system as a result that the standard errors of the Bragg wavelength are less than 14 pm.Then,the eight-month strain monitoring data illuminate that alternation of dry season and rainy season as an important factor is the reason in strain fluctuation of monitoring spots and rainy season as the main reason for the increase of strain change.Finally,an important monitoring position is determined;and the secondary lining of the tunnel is stable at present.The achieved results show that the FBG is good at measuring strain distribution of tunnels due to its excellent characteristics compared with traditional electromotive sensors and other optical fiber sensors.As a result,it is a feasible and effective method for structural health monitoring and damage detection of tunnels.