Experimental Investigation on Grouting Repair in Operational Shield Tunnels

Objective After a significant cross-sectional deformation of shield tunnel structure, using internal tension steel ring reinforcement and the like will incur substantial material and labor costs. Improving the stress conditions of the shield tunnel structure and proactively correcting deformations through secondary grouting is a more economical approach. Therefore, it is necessary to conduct an in-depth study on the effectiveness of grouting repairing cross-sectional deformation in shield tunnel structure, as well as the structural response during and after grouting process. Method Field grouting tests are conducted in a shield tunnel of Wuhan Metro, peripheral strata defects, structural cracks, and convergence deformations before and after grouting are measured and compared. The law of tunnel structure convergence deformation and horizontal displacement changing over time after lateral grouting inside tunnel structure is analyzed in-depth. Result & Conclusion The test results demonstrate that the effectiveness of lateral grouting inside the tunnel in repairing ground defects, addressing tunnel structural cracks, and correcting significant cross-sectional deformations. The distribution pattern and time-history development of convergence deformations and horizontal translations of the lining ring under grouting load influence are revealed. During grouting process, the lining ring at the grouting point exhibit a ′vertical-ellipse′ deformation convergence trend. Approximately 2.5 hours after grouting, the lining structure exhibits some rebound in ′vertical-ellipse′ convergence deformation due to the grout shrinkage, and the deformation trend further continues. Around 20.0 hours post-grouting, the tunnel structure convergence deformation will be basically stabilized.