The importance of drainage system in railway tunnels and possibilities to reduce the LCC
This paper will present the current state of drainage systems in new and existing SBB-railway tunnels. The fundamental drainage concepts, their limits as well as the LCC will be considered. The problems linked with the water pressure, its quantity and chemistry which may vary along the length of the tunnel will be described. The importance of both accessible and non-accessible elements, like, for example, the advantages of an extensive gap between the lining extrados and the excavated rock mass will be shown. A drainage system should ensure the permanent safe drainage without formation of any local water pressure behind the lining or the invert. An insufficient design concept or respectively construction mistakes may lead to premature failure of the drainage system. Moreover, as shown by experiences from older and newer tunnel, this causes often a sudden increase of the maintenance costs or even unplanned tunnel closures. The choice of appropriate design and materials as well as maintenance approaches play a primary role in preventing problems and reducing maintenance costs.