Monitoring and Analysis of the Internal Force of the Lining Structure by FBG Sensors

Wavelength division multiplexing (WDM) technology was adopted to form a linear chirped fiber Bragg grating (FBG) sensor array in series for continuous monitoring of the strain to the secondary lining of a typical tunnel section. A large number of raw data were obtained that are helpful for understanding the conditions of concrete strain, structural internal force, and distributions and variations. The data also allow for the analysis of the reliability of the lining structure and the discovery of potential safety hazards in the tunnel lining in order to prevent the tunnel from losing stability during construction. The variation regularities of early concrete strain and structural internal force of the secondary lining were obtained by plotting and analyzing the curve diagrams of the internal force vs. time. The practice shows that this highly precise method can be applied to tunnels with adverse environmental conditions and can be widely used for the site testing of tunnel structures.