Impact on Existing Tunnel Due to Construction of New Shield Tunnel in Close Proxomity

During the construction of small spacing shield tunnel in Tianjin soft ground, the magnitude of the advanced tunnel stresses and deformation changed. It was written according to the engineering project of Tianjin metro with the smallest interval of 0.98 m. Stiffness migration method was employed to simulate the process of the new-construction tunnel, considering the soil reinforcement. The displacement of surrounding soil, internal force and displacement of the existing lining segment was analyzed and predicted. The calculated results were compared with the measured data, and the variation of the internal force and displacement was summarized.Resultsshow that the grouting reinforcement largely reduced the displacement and internal force of the existing tunnel, but might produce certain mutations when just entering the reinforced region. It should be monitored during the tunnel construction.