Geotechnical input essential for power waterway design

Understanding of the ground complexity and rock mass behaviour are essential for optimal geotechnical design of underground structures. The recommendations of the Austrian Geotechnical Society define procedure and parameters important for underground design, with special concern on the parameters vital for the excavation and the primary support. The power waterway final lining design follows the recommendations, but different key parameters become essential. The primary state of stress, the rock mass deformability, permeability, and maximal and minimal groundwater levels are key design parameters for type determination and design of the final lining. These parameters have to be refined during all design phases and, if necessary, additionally investigated. A framework identifying and evaluating key variables controlling pressure tunnels behavior and defining suitable lining types have been discussed. Importance of the key parameters, possibility of their definition and experience from different projects are put in relation with the most used final lining systems.