Concerning the problem of the seismic stability of the Nurek dam

1. The comprehensive investigations and calculations performed by many research, planning, and surveying organizations and universities of the country by means of modern, sufficiently substantiated methods in strict conformity with the requirements of the existing design standards showed [4] that the seismic stability of the Nurek dam constructed in an intensity 9 earthquake zone is provided without the installation of antiseismic collars. 2. The conclusions about the insufficient seismic stability of the Nurek dam and need for its reinforcement by antiseismic collars are a consequence of an unjustified overestimation of the calculated seismic actions used for its design, considerable underestimations of the design characteristics of the shearing resistance (strength) of its materials, and use of simplified methods of calculating its seismic stability. 3. The variant proposed by the authors of [7] for increasing the seismic stability of the upper part of the dam by its dicrete reinforcement with reinforced-concrete seismic collars leads to substantial inhomogeneity of the reinforced zone of the structure, which under intense seismic actions may lead not to an improvement but to a worsening of the working conditions of this zone of the structure. The need for and effectiveness of this measure was not proved by investigations and quite simplified calculations. It is seen from the results of dynamic calcualtions of the stress state and deformations of the dam even with overestimated accelerations of the foundation with the use of two different dynamic models of the soil that reinforcement of the upper, near-crest zone of the structure does not have an effect on shear of its large (in volume) upper part along deeper surfaces of sliding. The assertion of the authors of [7] that “the technical decision on reinforcing earth dams by means of structural measures of the antiseismic type, accomplished at the Nurek dam, is reliable, cost effective, and quite promising” essentially has no grounds.