ABSTRACT
The construction of the curtain and drainage for rock and earth dams from galleries arranged at dam foundation maybe regarded as a successful solution. Draglines or special machinery are used for construction of counterseepage soil walls in dam foundations. Permeability can be reduced and the strength properties of large rock bodies at dam foundations may be improved by cement grouting, silicatization, cold or hot bitumization, and pressure filling in deep boreholes with clay or other materials. For instance, a stratum of rock salt (NaCl) the leaching of which could bring about displacements of rock bodies in the dam foundation is encountered beneath the upstream prism of Rogun Dam. In any case, the seepage prevention constituents of dam foundation should guarantee a sufficiently long time of leaching, not less than 50 years counted from the incipient seepage to the time of the exit of leaching front into tailwater; this time depends on the class of permanent structures.
