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1. The placement in a dam of horizontal earthquake-proofing layers of soils whose dynamic moduli of deformation are lower than for the main soils of the structure makes it possible to alter purposefully the dynamic characteristics of the dam (natural frequency and modes of oscillations), to reduce the level of the seismic load on the structure within given limits, and to restrict the distribution of zones of the limit state. 2. The presence of one earthquake-proofing layer directly at the base of the dam or of several layers alternating with the main soil located at a height up to 0.5Hd from the base can reduce the level of the seismic load on the structure by a factor of 1.5–2. 3. By varying the location of the earthquake-proofing layers over the height of the dam it is possible to locally influence a change in the level of the seismic load on the structure and dimensions and location of zones of the limit state. 4. The investigated design measures can effect a savings in certain cases due to using cheaper soils for the earthquake-proofing layers compared to the main soils of the dam, and mainly due to depressing the profile when providing its seismic stability. 5. The investigated designs are sufficiently efficient technologically, and their practical realization is not related to any changes in traditional construction methods.

The 300-m-high Nurek dam was designed and constructed with compressed, economical profile with a steepness of the upstream slope of 1:2.25. Modern earth dams in seismically active regions are often designed with flatter upstream slopes. Longterm investigation into the design and construction of the Nurek dam have made possible considerable progress in solving the problem of increasing the reliability and earthquake resistance of high earth dams being built in regions with high seismicity. The Nurek dam was constructed with a high earthquake resistance in conformity with standards. The technical decision on reinforcing earth dams by means of structural methods of the antiseismic collar type, accomplished at the Nurek dam, is reliable, cost effective and promising. The authors conclude that it is expedient to continue the development and investigation of such measures and to broaden the sphere of their use.