ABSTRACT
The loading on concrete linings of pressure tunnels and shafts by external water pressure is strongly influenced by the permeability conditions of the lining and rock mass. The outdated assumption, that the concrete lining is absolutely tight and the external pressure is fully acting on the lining, results in a very conservative design of the lining thickness. The herein described design approach shows, that if loosened rock zones with increased permeability in the vicinity of the tunnel are present, the external water pressure effectively acting on the lining increases and the limit has a value equal to the water head. Therefore it is in such situations even more important to carry out consolidation grouting, which considerably reduces the external water pressure effectively acting on the lining.
