Inversion model for mechanical status of longitudinal joints in shield tunnel

The mechanical status of longitudinal joints in shield tunnel during operation is an important index for structural evaluation. For most of the tunnels that are not pre‐embedded with monitoring elements, only a few indicators can be measured directly during daily inspections. To comprehensively evaluate the deformation and mechanical status of the tunnel, an inversion model of the longitudinal joints, which is based on the measured convergence deformation of the shield tunnel, is proposed. First, the joint rotation deformation is determined using the successive rotation method. Then, the internal force of the joint is obtained based on the joint deformation. The two steps of the model are coupled with the iterative process for obtaining the accurate position of the joint neutral axis. The proposed model is verified by full‐scale ring test. It provides a new approach for obtaining the tunnel mechanical status and thus lays a theoretical foundation for decision‐making with regard to tunnel maintenance.