About the design of new or recalculation of existing inner linings of tunnels taking the non-linear material behaviour of concrete into account

In underground constructions, soil and rock act as a loading and load bearing element at the same time. This is especially the case for tunnel linings embedded in soil and rock. Therefore, for the practical application of non-linear methods for the design of tunnel shells, it is of major importance to develop a safety concept free of contradictions. Based on the experiences of several tunnelling projects where non-linear calculation methods have been applied, an overall approach for the verification of the lining in ultimate limit state and serviceability limit state is presented. The concept is especially fit for the analysis of unreinforced or lightly reinforced tunnel shells and for the verification of existing tunnel linings as it is able to activate additional system capacities. Currently the analysis and verification of existing tunnels has become increasingly important. Thus, the retro-fitting of tunnels with the objective of meeting new safety standards, such as the German RABT 2006, is always associated with an assessment of the existing linings and their current structural condition. On this basis, necessary renovation and repair work can be planned. The proposed verification concept is also fit for this purpose.