Field observations of the 40-year-old dam suggest good quality of construction-assembly work and professional operation of the power plant.The concrete dam of the Krasnoyarsk hydroproject is a gravity structue with discharge chambers 4 -6 m wide in the base, a vertical thrust face, a downstream face inclined at 1:0.76 in the powerhouse section, and at 1:0.8 in the remaining section of the dam (Fig. 1). It has a maximum constructed height of 128 m, and length of 1072.5 m along the crest. The body of the dam is cut into sections 15 m wide and columns 11.5 m long. The expansions joints between the sections are sealed by keys formed from metallic sheets and grouting of a portion of area of the joint in lieu of the asphaltic keys normally employed. The granite rock bed beneath the lower surface of a heavily grouted curtain extends to a depth of up to 60 m. Weep holes are situated 5 -7 m from the upstream face, and are continued for 30 -40 m into the rock bed.The first generating sets at the plant were started in November 1967, and the hydroproject was placed in continuous service in 1972. In this paper, it is our intention to trace how the basic diagnostic indicators of the dam's condition have changed after 40 years of service.Information on the average strength characteristics of the basic grades of concrete, which were obtained during construction, and from recent measurements is presented in Table 1.A negligible decrease in strength has occurred on the outer faces of the dam in a layer with a thickness of up to 100 mm. The concrete in the split abutment, separate bulkheads of the bottom (construction) discharges, and the slab stabilizing the right bank in the immediate vicinity of the discharge section of the draft tubes of the generating sets has been largely subject to deterioration to a depth of up to 200 mm in the zone of variable water level on the downstream face.Use of special medium-thermite cements from the Krasnoyarsk Cement Plant, which had been developed for waterdevelopment works in Siberia, has contributed heavily to the

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