The dam at the Serebrynka-I hydroeIectric plant belongs to the ciass of high rock-earth dams with cores. The maximum height of this dam is 78 m, and its crest length is 2400 m. Its construction was carried out under thesevere climatic conditions of the Far North during the period 1966 to 1971.The material used for the supporting shells of the dam was ran-of-quarry rock placed in layers up to 18 m high, without applying special compaction measures. The core was constructed from moraine soil placed in water. The transition zones between the moraine core and the shells consisted of a layer of sand-gravel-pebble material ranging in thickness from 6 to 18 m. At the lower elevations, the downstream transition zone was a two-layer inverted filter. The construction of the dam is shown in Fig. 1.The dam core was placed in 100-200-m long courses, whose width was equal to the core width at the elevation at which the work was being carried out. The height of each course was 3 m. Dikes were constructed along the perimeter of each course, and water was then pumped in to a depth of 2-2.5 m. The moraine soil was placed in the artificial pools thus formed. After placing each course in the core, the pool for the next course was formed in the same manner, and so on.During the winter, the pools were not entirely filled with soil. Along their perimeter, the constructors placed only 6-10 m wide strips. The dikes for the next courses were constructed on the previously placed strips, the water level in the pools rose 3 m, and strips were placed again along the perimeter. Thus, over the entire winter period the middle part of the core remained under water and was not subjected to freezing. The maximum depth of the pools was 2.5 m. The water temperature in the pools was kept above freezing by pumping in hot water from an electric boiler. The shells were placed simultaneously with the core.Experience with the construction of the Serebrynka-I hydroelectric plant has been partially described in the literature [2, 5, 6]. In this article, the writer describes briefly the results of full-scale observations on the pore pressure, seepage, and settlement in the dam during its construction and operation.

The construction of hydro developments with high dams of large volumes lasts, as a rule, more than !0 years, which leads to immobilization of capital investments and reduction of their effectiveness in the economy.To avoid this, capacities are started up at intermediate heads with the dams still under construction, sometimes with the use of temporary runners. For example, the staged start-up of units of a hydroelectric station whose construction is being completed made it possible to produce additionally about 33 billion kWh of electricity during five years.The staged putting of structures into operation is specified by the design. A limit level of filling of the reservoir and minimum allowable profile of the dam ensuring satisfactory operation of the structure at the acting head are established for each stage. When assigning the dam profile of each stage it is assumed that, with consideration of staged construction, the stress--strain state of the dam of the complete profile at the normal pool level (NPL) will correspond to the calculated design assumptions.Among structures put into operation in stages are the dams of hydroelectric stations: the Sayano-Shushenskoe gravity-arch dam and the Nurek eartPr-rock dam.The Sayano-Shushenskoe gravity-arch dam with a height of 242 m and crest length of 1066 m has a base width of 105.7 m and crest width of 25 m. The dam is divided lengthwise by contraction joints into sections about 15 m wide. The sections consist of 27-m-long columns. A grout curtain I00 m deep and a drainage system are constructed in the foundation of the dam.The dam is located in a canyon with steep walls (800-900 m above the waterline).Its foundation is composed of schists.The climate of the construction region is markedly continental, the seismicity is 6-7.To monitor the work and state of the dam during construction and temporary and permanent operation, it is equipped with a considerable number of monitoring and measuring instruments. A monitoring system is created on the structure, which consists of about 3000 embedded sensors for determining deformations, temperature, and seepage pressure in the concrete, a piezometric network, a number of geodetic instruments, and devices for measuring displacements of the structure and rock foundation.The staged start-up of the dam requires timely cooling of the concrete masonry to the temperature of grouting the column and radial joints, promptintervention in the technology of constructing the structure, and effective checking of the curing of the placed concrete, which under conditions of Siberia is one of the primary problems.For this purpose, additional embedded telethermometers were installed in the dam.For provision of on-site observations, regulation of the temperature regime of the dam, and provision of timely sealing of the concrete masonry of the dam, a special service was created at the construction site which works in close contact with design and research institutes. One of the tasks facing the service was a determination of the effect of the temperat...

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The core of the dam was constructed" by dumping moraine soil into water. The builders successfully solved, in so doin~ the problem of year-round conducting of operations, and the technology of dumping the soil improved constantly. During the summer the dam core was dumped into individual pools with a length of 100-400 m, a width equal to the width of the core at the operating elevation, and height of 3 m. The pools were embanked about their perimeters and filled with water to a depth of 2-2.5 m. The moraine soil was dumped into these ardfical pools. Dumping was done by the "pioneer method" with a wide front and the pools were filled with soil over the entire area. After dumping one layer of the core, pools were created in the same way for dumping the next layer, etc. The thin above-water soil layer (0.5-0.8 m) was compacted by the repeated runs of the dump trucks over it.Unlike the summer technology, during the winter the moraine soil was dumped only as strips with a width of 6-10 m, running along the perimeter. The embankment of the next layer was placed on the dumped strips, the water level was raised 3 m, strips were dumped about the perimeter, etc. A pool with a depth to 12 m was created. Thus, the middle part of the core was always under water and did not freeze. The soil, freezing to a depth of 30-50 cm, thawed rapidly when the water level in the pool was raised by the next 3 m. Elec=ic thermometers embedded in the frozen soil showed that thawing occurred within 5-10 days.The reduction of the usual demands imposed on the material and method of dumping the rock shoulders was due to the design of the dam, which provides, as it were, independent settlement of the shoulders and core with slippingalong thetransitional zones.The high category of the dam and the characteristics of its construction required thorough investigations to evaluate the granulometric composition of the soil in the structure and, in particular, to solve the problem of qualitative substantiation of the winter method of constructing the core. The main indices of the quality of the soil placed in the dam core were: a) dry unit weight of the soil and its fines (fraction smaller than 2 ram); b) relative density and void ratio; c) granulometric composition; d) water impermeability. During construction of theSerebryansk dam about 3000 samples of the moraine soil were taken and tested.For comparability of the quality of the summer and winter dumped fills and for evaluating the degree of inhomogeneity of the core body with respect to density, impermeability, and granulometric composition, the core was conditionally divided in zones I-VII (Fig. 1)depending on the time of placing the soil, and the indicated characteristics were determined for each. The demity characteristics of each of the zones are represented by curves of the distribution of the values of the dry unit weight of the soil and of its fines (Figs. 2 and 3). The average values of the dry unit weight of the core soil corresponding to 75 and 5090 were respectively 2.03 and 2.10 tom/m 3. V...

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