Competitive pumped-storage projects with vertical pressure shafts without steel linings

For the highly loaded pressure tunnels and shafts that are used for the extension of storage power plants with pumped storage and to increase installed capacity, alignments of the waterway system with high overburden are of great importance from the economical and safety points of view. With the development of the raise-boring method, vertical pressure shafts can now be drilled up to 800 m in one step. Considering rock cover, the use of vertical pressure shafts can enable optimal alignments. If the vertical shaft is located deep enough in the rock mass and safety against hydraulic jacking can be ensured, no steel liner is required in the shaft as long as rock permeability is low, and a reinforced concrete lining is sufficient. This is designed in order to limit crack widths and thus keep water losses below acceptable values. In view of highly increasing steel prices, such a concept results in economic and competitive pumped-storage projects.