Deformation Monitoring and Performance Analysis on the Shield Tunnel Influenced by Adjacent Deep Excavations

Abstract

The health monitoring and analysis on the metro tunnels are very important because the metro system is the lifeline of metropolises and the shield tunnels are easily affected by adjacent constructions. In this paper, health monitoring on the deformation of operating metro shield tunnels influenced by a close deep excavation is investigated with a case in Shanghai. Both manual and automatic measuring methods were adopted in the safety monitoring during deep excavation, and the results of both methods are compared to analyze the deviation of measuring methods. Comparison shows that the automatic monitoring results could be affected by poor working conditions and cumulative error. It is suggested that different monitoring methods should be verified against each other to ensure the reliability and accuracy of the monitoring results. Based on the distribution of tunnel settlements, the curvature radius of tunnel deformation is obtained by the cubic B-spline method and then used in performance analysis on the tunnels. The relationship between the settlements and horizontal convergences of the shield tunnels are also studied, which shows a significant correlation. Analysis shows that there is no significant relationship between the curvature radius and settlements of the tunnel, which means monitoring and controlling the settlements plays an important role in protection of the tunnels but cannot guarantee the safety of tunnels. The real-time data of the curvature radius should also be calculated and analyzed in health monitoring and performance analysis on shield tunnels.