No abstract

Adjacent tunnel construction and environmental disturbances can lead to longitudinal deformation in pipe-jacking tunnels. The longitudinal deformation of the tunnel is closely related to the occurrence of joint dislocation, joint opening, and other defects. In view of the difficulty of obtaining 3D longitudinal deformation curves, a method is proposed to obtain 3D longitudinal deformation curves based on a large number of 3D point cloud data with high spatial resolution and large spatial dimensions. Combined with the mechanism of defects occurrence, a theoretical basis for tunnel defects assessment based on tunnel longitudinal deformation is proposed. Taking one pipe jacking tunnel as an example, the longitudinal settlement curve and the 3D longitudinal deformation curve are compared. The correlation between the 3D longitudinal deformation curve and defects such as mud leakage, cracks, and differential deformation is illustrated from the perspective of three indexes: deformation amount, bending deformation, and shearing deformation. The accuracy and reliability of the 3D longitudinal deformation curve in tunnel defects detection and assessment are verified.

The maintenance of in-service shield tunnel lining has become a critical issue in recent decades due to the rapid development of the metro system in China. The external load is one of the most important factors influencing the deformation and performance of the in-service shield tunnels. It is hard to evaluate the external load since it is influenced by complex factors. And the arbitrary-distributed external load is not considered in the existing theories. A novel back-analysis approach for evaluating the external load using the deformation of tunnel lining was proposed based on Betti’s theorem. The theoretical rationality of the proposed method is analyzed, and the workflow is provided. The data and simulation models for a model test were adopted to validate the effectiveness and accuracy of the proposed method. The results show that the external loads can be back-analyzed with satisfying accuracy and low computational cost. Then, the practical application was conducted for an in-service shield tunnel. In addition, the workflow combined with laser scanning and back analysis was proposed for evaluating the practical loads. The proposed approach can be used for the back analysis of the external loads based on lining deformation scanned inside tunnels, with good performance.