Numerical Simulation of Effect of Foundation Pit Excavation on Underlain Shield Tunnel

In the background of a foundation pit excavation project on Yanan Road in Hangzhou City, this study simulated the excavation of foundation pit above an underground tunnel using 3D MIDAS/GTS software. The combined action of foundation pit, ground and tunnel were considered. The influence of foundation pit excavation on the deformation of underlain shield tunnel was evaluated and simulations were carried out on the effectiveness of different strengthening and control approaches. Results from the research showed that during the stages of piling and ground strengthening, settlement occurred at the tunnel; with the excavation of foundation pit, uplift deformation at the bottom of the foundation pit and the tunnel increased; with stricter strengthening and control techniques employed, the magnitude of uplift at the tunnel and bottom of the foundation pit reduced, suggesting that various control procedures were effective to some extent.