Response of operating metro tunnels to compensation grouting of an underlying large-diameter shield tunnel: A case study in Hangzhou

Abstract

Due to the shield tunneling underneath, long-term settlements may develop in the existing metro tunnels. The compensation grouting is applied worldwide to stabilize the settlement of ground and existing structures. Few field studies concerning large-diameter shield passing tunnel from below have analyzed the interaction between the compensation grouting and the existing tunnel. This paper presents a case study on the response of the operating metro tunnels to the compensation grouting of an underlying large-diameter tunnel in muddy clay stratum. The tunnel deformations before, during, and after the compensation grouting were monitored and analyzed. The long-term tunnel settlements were mitigated and stabilized by the timely compensation grouting. Smaller settlement rates were observed during the grouting treatment, and the settlement was gradually stabilized three months after the grouting. The grouting holes at the tunnel invert were used initially for better grouting efficiency. The horizontal displacement and convergence developed during the grouting construction and remained stable after the grouting process. Moreover, some limitations of the grouting treatment were discussed. The tunnel settlement in the section close to the center-line of the south-line tunnel cannot be prevented effectively. The differential displacement cannot be reduced by this grouting program.

Keywords

• Grouting treatment
• Shield under-crossing
• Large-diameter shield tunnel
• Tunnel settlement