Investigation of the response of bored tunnels to seismic fault movement

The response of Twin Circular Bored tunnels (TBM) to seismic fault movement is investigated through three-dimensional finite element analysis. Both normal and reverse fault rupture is considered. The permanent tunnel lining is simulated with separate elastic rings of finite thickness. These rings are connected to each other in the developed finite element models using interface elements with equivalent material properties. The displacement of each elastic ring of the tunnels due to different seismic fault movements is computed and results are presented in terms of the absolute total, vertical and horizontal lining displacements and of the relative shear and normal displacements at the circumferential ring joints. Finally, simplified analyses in which the tunnels are modelled as continuous elastic tubes are also presented. Comparison of the results using the two modelling approaches shows that the conventional simplified assumption of continuous elastic lining cannot accurately reproduce the deformation of the tunnels due to seismic fault rupture.