Numerical Simulation of EPBM Induced Ground Settlement

Metro tunnel construction under high-density urban areas always poses the challenge of ground settlement which should be well predicted so that necessary precautions can be taken. An underground Metro line case study from Iran is used for the investigation. In this paper, an attempt has been made to predict ground settlement using available empirical and analytical methods. Significance of correctly estimating the parameters especially volume loss has been discussed. A numerical model is developed using the finite-difference-based numerical code FLAC3D to simulate tunnel construction using earth pressure balance shield tunnel boring machine (EPBM). The stage by stage construction sequence and EPBM parameters are simulated in this model. The ground settlement behaviour as the tunnel advances is presented as displacement contours and profiles. A critical comparison has been made among all methods used to predict the ground movement for the current case study. It was concluded that empirical and analytical methods are effective only if associated parameters like volume loss can be correctly ascertained. The numerical model was found to be the most reliable and useful tool for ground settlement prediction.