Convergence Deformation of Existing Shield Tunnel Induced by Adjacent Shield Tunnelling Construction

The subway system has benefited the transportation in a lot of modern cities with advantages such as convenience, rapidity, large volume, etc. However, with the construction of more and more subway systems, the underground space is increasingly crowded. According to engineering practice, existing tunnel is inevitably distorted by adjacent tunneling construction, reducing stability and safety, especially when the distance between two tunnels is small. To explore the convergence deformation of existing tunnels, field monitoring and analysis are conducted on the convergence deformation of the existing tunnel induced by the adjacent tunnel construction. This research finds that: (i) the convergence of each monitoring section gradually develops and stabilizes, and then the convergence of tunnel segments exhibits “horizontal duck egg” pattern and non-uniform convergence pattern; and (ii) after the tunnel shield machine passes, due to the lateral compression deformation of surrounding soil, horizontal convergence of the existing tunnel has an increase in horizontal convergence and a decrease in vertical convergence.