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...

During construction of the Serebryansk hydroelectric station-1 dam, the most labor-consuming operations were those required for construction of the impermeable part-the core of sandy loam moraine soft [1]. Most of the core (90~ was constructed by dumping soil into pools of water; the remaining volume (the narrow upper part) was placed by dumping soil of natural water content in layers. Both methods are "wet" processes and, therefore, the effect of low temperatures on the course of the operations is quite considerable, and placing the soft in the core in the winter was impossible without taking special measures. Among these was the use of chlorides for the following purposes: for summer preparation of the unfrozen borrow for dumping in the structure in the winter; b) for preparation of the foundations and surface in the winter for the dumped fill; c) for combatting freezing of the soil in the dump trucks and excavator buckets.The method of dumping soft into pools has proved itself at many hydro developments on the Kola Peninsula, both by the simplicity of the technology and the high quality of the embankment obu3ined [2, 3]. Under summer conditions the pools were constructed with a depth of 2-2.5 m, a width equal to the width of the core, and length to 400 m. Blankets of 2-3-m-thick soil constructed on the slopes of the previously dumped upstream and downstream transitional layers of the dam served as the embankment for the pools in a longitudinal direction and drydumped transverse dikes in the transverse direction. After filling the pool with soil the dikes were removed, since theirsoil was considered to be of inferior quality.Dumping of the soil into the pools, with a number of changes in the technology of the operations, was adopted by the builders also for constructing the dam core during the winter. Winter dumping differed by an increase of the depth of the pools, construction of the core in strips along the transitional layers, and delivery of heated water to the pools, which permitted year-round operation at almost the same rate [4]. However. during the first winter season serious difficulties arose because of freezing of the dry-dumped embankments; the longitudinal blankets, which froze during pool preparation, thawed as the pool was filled with warm water and flattened out in the underwater part, remaining above the water in the form of frozen "bars'. As a result leaks formed in the blankets, which sometimes were so appreciable that it was impossible to raise the water in the pool to the necessary level. "the embankment transverse dikes did not leak owing to their greater thickness and better compaction, but their removal required preliminary loosening by drilling and blasting.Using the first winter season experience of core construction, by the second season the builders introduced modifications into the technology of operations, one of which was making the embankments of salted nonfreezing soft which eliminated the difficulties. There were no leaks in blankets of such soil, since on filling the pool fla...