Structural responses and treatments of shield tunnel due to leakage: A case study

Abstract Structural performance of shield tunnels is of paramount concern during their long-time service. This work presents a case study describing the structural responses of a shield tunnel caused by unexpected leakage and the corresponding treatment measures. Firstly, the general information of the accident is introduced, and the structural responses of segmental lining are highlighted, e.g., longitudinal differential settlement, horizontal convergence, dislocation among rings, and concrete spalling. On this basis, the influence mechanism of leakage on the structural responses is preliminarily discussed. Finally, the treatment measures are proposed and their effectiveness is evaluated by field application. The research results show that the structural response caused by leakage is mainly differential settlement, but the horizontal deformation is not significant. The differential settlement further causes dislocation among rings and concrete spalling. The maximum settlement of the lower line tunnel and the upper one occurs at the special lining rings where the leakage occurs, and the maximum values are 580.4 mm and 301.3 mm, respectively. There is no dislocation among the special lining rings. However, severe dislocations of about 10 ordinary concrete segmental rings are observed on both sides of the special lining rings. The value of the dislocation increases first and then decreases when approaching closer to the special lining rings. Correspondingly, the concrete around the circumferential joints is also severely spalled. The greater the dislocation, the more severe the concrete spalling. The longitudinal differential settlement and dislocation among rings are effectively controlled by the proposed measures, mainly including polyurethane grouting and bonding steel plates by full-ring and across circumferential joints. The case presented can be used as a reference in similar conditions.