Numerical study on responses of an existing metro line to staged deep excavations

摘要

Responses of a substructure adjacent to deep excavations are complex, especially when the substructure is connected to the supporting systems of the excavations. In this study, a three-dimensional (3D) numerical model is developed by finite difference (FD) software, FLAC3D v5.0, to examine the responses of a metro line to deep excavations through a case history in Shanghai, China. The developed numerical model includes four deep excavations, which were located at two sides of the metro line and were connected to the structures of the metro station. These deep excavations were constructed in stages and the construction processes are simulated in accordance with the practical execution. Responses of the rails to the deep excavations are illustrated and the numerical results are compared to the measured data to validate the developed numerical model and input parameters. Moreover, 3D structural responses of the metro station and shield tunnels to the deep excavations are presented and analyzed. Numerical results indicate that (i) the walls of the station move upward during the excavations and the slabs are uplifted by the walls; (ii) The station heaves significantly whereas the shield tunnels settle slightly. (iii) The station will be distorted if the unloading is asymmetric.