Monitoring of tunnel excavation based on the fiber Bragg grating sensing technology

Abstract

The application of advanced sensing technology is of great significance for investigating the disturbance caused by tunnel excavation. In this paper, fiber Bragg grating (FBG) sensing technology is introduced into tunnel construction. To monitor the deformation in the surrounding soil, an FBG inclinometer based on the conjugate beam method is developed and then validated by laboratory calibration. Then the laboratory model test is carried out according to the actual tunnel excavation of adjacent piles. FBG-based inclinometers are used in the model test to measure the deformation of the surrounding soil, and FBG sensors are attached to the piles to monitor the pile disturbance induced by excavation. The results show that the horizontal displacement of the soil on both sides of the tunnel is distributed symmetrically up and down with the centerline of the cross-section of the tunnel. The stress redistribution of the soil above the tunnel causes a more significant surface settlement than the subsurface settlement. Moreover, the displacements of the existing piles decrease with depth and are more susceptible to the excavation sequence. Additionally, this study confirms that FBG sensing technology is suitable for monitoring tunnel excavation.