Stability analysis of an urban tunnelling in difficult ground condition

This paper presents the results of stability analysis of an urban tunnelling in difficult ground conditions under a high hydraulic head aiming at evaluating appropriateness of the initial design and identifying potential problems arising from the tunnelling. In order to realistically capture the mechanical and hydrological interaction between the tunnelling and groundwater, a fully coupled 3D stress-pore pressure finite element model is adopted. Using the 3D model, the tunnel deformation and support stresses, and building response during tunnelling are evaluated. Based on the results, the appropriateness of the initial tunnel design was evaluated in terms of the support pattern, grouting scheme, and excavation method. Also highlighted is the importance of carrying out stress-pore pressure coupled analysis for tunnelling cases involving high hydraulic heads.