The technical lifetime of underground structures does not only depend on the long-term behaviour of individual support elements and material characteristics but also on various boundary conditions, which influence the entire long-term system behaviour of the structure. Latest by April 2019 all road tunnels with a traffic load of more than 20,000 vehicles per day must have two tubes due to the requirements of the tunnel safety law (STSG). Thanks to the construction of second tunnel tubes and the corresponding cross passages sampling of support materials including membranes was possible. The paper presents outcomes regarding the long-term behaviour of support elements and membranes. To evaluate the stresses and the supporting effects of the tunnel shells flat-jack tests and different simulations were performed. The results presented can be used as a basis for future designs.
Tunnels are an indispensable part of modern transport infrastructure. As multi-generation structures their long-term preservation as well as their technical service life is of central importance.
The current state of research in the field of durability of structural elements must be considered separately. In almost all areas a prediction of materials and structural components towards lifetime exists. System-wide investigations were rarely performed, so that there is no technical lifetime consideration of the outer lining in systems included.