Structural safety analysis of shield tunnels based on convergent deformation

Purpose Damage to the pipe structure and increased bolt stress in operating tunnels will significantly affect the long-term stability of shield tunnels. However, due to the large number of segments and complex bolt installation methods, it is difficult to directly obtain the conditions of segments and bolts. Convergence deformation, as an important indicator for the health assessment of operating tunnels, is easy to collect and can directly reflect the structural state of tunnel segments and bolts. Design/methodology/approach Taking the typical sections of Hangzhou Metro Line 1 and Line 3 as an example, the current structural damage is simulated by monitoring tunnel convergence deformation. First, based on the disease data, the relationship between convergence deformation and segment leakage, segment misalignment as well as the longitudinal joint opening between two segments is analyzed statistically. The stress of bolts, steel bars and segments under different convergence deformations is simulated by Midas. Then a reinforcement measure of circumferential internal tension steel rings is proposed. Findings It is found that when the segment convergence exceeds 85 mm, although the overall force on the segment has not reached the material limit, there are certain safety risks in the structure. After comparison, the reinforcement measure has a relatively significant effect on controlling the lateral deformation of segments. Originality/value The results have important guiding significance for the evaluation of structural diseases, early warning and control of structural diseases at different convergence deformations.