基于光纤传感技术的地铁隧道冻结法施工监测

为了掌握地铁隧道联络通道冻结法施工中冻土的温度场和应力场,提出一种基于光纤布拉格光栅(FBG)传感技术的冻结法施工实时监测方法.在低温潮湿工作环境下,FBG传感器比传统电子式传感器在精度、灵敏度以及稳定性等方面存在较大优势.基于此,首次提出了整合FBG传感器的冷冻监测管设计方案及安装方法.通过在联络通道冻土帷幕左右两侧监测孔内布置FBG传感器,对冻结法施工过程中的冻土温度和应变进行实时监测.根据FBG传感原理并采用小波变换去噪方法对原始温度和应变监测数据进行分析,获得了冻土温度和应变沿厚度和深度方向的分布模式,为进一步认识冻土帷幕的形成和发展规律提供依据.

Monitoring of metro-tunnel freezing construction using fiber sensing technology

In order to grasp the temperature and strain fields of frozen soils during freezing construction of the metro-tunnel cross-passage, a method for real-time monitoring of freezing construction using fiber Bragg grating (FBG) sensing technology is proposed. Under the condition of low temperature and high humidity, FBG sensors have the advantages in terms of accuracy, sensitivity and stability in comparison with the traditional electrical sensors. In this connection, the design scheme and installation method of a novel freezing monitoring device integrated with FBG sensors is addressed. FBG sensors are deployed in freezing monitoring holes at both sides of the frozen soil wall of the cross passage to timely monitor the temperature and strain of the frozen soils in the process of freezing construction. The original temperature and strain monitoring data are analyzed based on the FBG sensing principle by use of the wavelet transform de-noising approach. The distribution pattern of the temperature and strain of the frozen soils in thickness and depth directions are recognized, which will provide a basis for further digesting the formation and expansion mechanism of frozen soil walls.