Resistance against internal erosion of various types of cut off walls in dam construction.

As part of the scheme to deviate water from the Altmuhl and Donau region into the Regnitz-Main area, six dams are in the process of being constructed south of Nuremberg. The earth dams are founded on silty to gravelly sands. According to the particular requirements, slurry membranes, one phase cut off walls or two phase cut off walls were executed as ground seals. Describes the laboratory investigations for the determination of the safety against erosion. For the applied material composition of the slurry membrane a limit gradient of i = 200 was determined, the limit gradient of the one phase cut off wall reduces to i = 100, for the two phase cut off wall with a considerably higher content of solid material the limit gradient turned out to be i = about 300. If these limit gradients are exceeded, failure of the sealing wall due to erosion has to be anticipated under conditions of permanent loading. (from authors' abstract)