A Method of Monitoring the Cross-Section Deformation of Tunnels Using the Strain Data from the Fully Distributed Optical Fibre Sensors

Abstract

Fully distributed optical fiber sensing technology allows the high-density strain to measure the overall curvature and cross-section deformation of tunnels. However, there are few studies on the use of longitudinal strain along the tunnel to measure the cross-section convergence deformation, and the method of obtaining the strain along the tunnel loop is costly. To address this issue, a method of monitoring the cross-section deformation of tunnels using the strain data is proposed. First, a model of the relationship between strain and deformation in tunnels is constructed to obtain the overall settlement using the longitudinal strain. Second, based on the finite element method (FEM), the deformation law about the strain measured points and non-measured points on the cross-section of the tunnel is proposed, and on this basis, the correlation coefficient is presented. Using the product of overall settlement and correlation coefficient, the cross-section deformation at non-measured points is obtained. The results of numerical examples shown that the proposed method can effectively expand the monitoring scale and realize high-density cross-section deformation measurement of tunnels.

Assessment of Tunnel Lining Stability through Integrated Monitoring of Fiber Bragg Grating Strain and Structural Deformation

“…Zhu et al [ 19 ] deployed seven strain gauges equidistantly along the circumferential section of a mountainous tunnel under complex geological conditions to measure structural strain and analyze construction safety. Ma et al [ 20 ] used fully distributed fiber optic sensing technology, laying four optical cables from the entrance to the exit of the tunnel. These cables were positioned directly above, below, east, and west of the shield tunnel to measure structural strain and analyze tunnel convergence deformation.…”