Full 3D Modeling of Tunnel Excavation and Lining with Emphasis on Sequence Excavation,Comparison of 3D and 2D Analysis

In this paper 3D and full tunnel modeling with considering step by step excavation and installation of lining, will be discussed. Full 3D modeling of tunnel by finite element method (FEM) can be ideally represents the behavior of longitudinal and transverse ground settlement by progress of excavation and installation of lining. Results of numerical analysis showed good agreement with empirical formulations for longitudinal settlement. It is also seen that the effect of boundary condition of the model, there are up to five times the diameter of the tunnel and then reaches its maximum and steady-state condition. With increasing the tunnel depth, ground surface settlement decreases before the tunnel face and increases after the tunnel face. Also according to the results, settlement longitudinal curves of different depths intersect in the tunnel face, which means ground surface settlements in the tunnel face are the same for different depths. In the other section of the paper transverse settlement curve obtained by 2D analysis compared with the corresponding trough from 3D analysis, by comparing these two profiles area, can be reached to the stress release factor, that is one of the key parameters in the 2D analysis.