Experimental Study on Deformation Behavior of Shield Tunnel Subjected to Riverbed Scour Based on DOFS

Exploring the deformation behavior of shield tunnels is significant to design and safety assessment for shield tunnel structures. This paper carries out a reduced scale model test of shield tunnel subjected to riverbed scour for the first time. A new loading device system is designed to simulate the initial stress field of stratum and effect of riverbed scour. Distributed optical fiber sensing (DOFS) technology is adopted as measuring method to achieve the surrounding soil deformation and structural deformation, ovality, and radius of curvature of shield tunnel. The test results show that uneven rebound deformation of stratum and shield tunnel structure occurs in both transverse and longitudinal directions under the action of riverbed scour. Variations in ovality differences exist along the longitudinal direction of the shield tunnel, indicating that the transverse and longitudinal deformation of the shield tunnel affects each other. The radius of curvature of the longitudinal deformation of the shield tunnel at the vault is much smaller than that of the bottom. The results demonstrate the broad application value of DOFS technology in shield tunnel structure monitoring and reveal the deformation mechanism of shield tunnels subjected to riverbed scour, which can provide important reference values for the structure design and safety monitoring of shield tunnels.