This thesis uses the finite element method to investigate the effect of tunnel support deterioration on the performance of tunnels. First, different methods to simulate tunnel excavation and the installation of a dual-lining system (primary shotcrete shell / secondary cast-in-place concrete inner lining) using the general-purpose finite element program ABAQUS are discussed. The second aim of this study is to understand the influence of long-time deterioration of tunnel supports and its impact on the stability of the combined support system (surrounding ground, shotcrete shell and inner liner). Using a parametric study, different deterioration processes are simulated, assuming elastic as well as elasto-plastic material behavior. This includes the simulation of tunnel excavation, the interaction between the shotcrete shell and the ground, and the interaction between the shotcrete shell and the inner lining. This allows one to interpret the main characteristics of the analyzed deterioration processes on the basis of the obtained stress distributions and displacements of the support elements.