Intense construction of earth dams with the maximum use of local construction materials has been observed in recent years in world dam constructlon practice. The volume of soils being placed in dams amounts to many millions of cubic meters. Therefore even a slight decrease of their construction cost has a substantial economic effect and increases the technical and economic indices of hydrostations being planned or under construction.Improvement of the construction of earth dams is accomplished by more progressive equipment and more economical construction methods [i].The following main methods of constructing earth structures presently exist in hydrotechnical construction practice: the method of layer-by-layer placement with mechanical compaction, hydraulic filling, and method of placing the fill in water.The method of placing fill in water eliminates certain difficulties due to the physical and mechanical properties of soils being placed under various construction and climatic conditions and has the main advantages that, compared to the hydraulic filling method, it is more convenient in a production respect and, furthermore, makes it possible to construct structures of many clay soils and, compared with the mechanical compaction method, it does not require the costly operation of compacting mechanisms and has a more productive placement of fill, This method was developed for the first time and introduced in practice in the USSR on the construction of dams of moraine soils in Karelia and on the Kola Peninsula The experience of constructing earth structures shows that the use of the method of placing fill in water is possible for various types of clay soils, from loess and moraine loamy sands to dense clays, and also soils of any degree of lumpiness are suitable: from a tecturally uniform powdery state to large lumps difficultly amenable to mechanical crushing. Low-strength rocks with a compressive strength less than 15 MPa are finding wider use in the construction of earth dams in the USSR and abroad. They include naturally disintegrated rocks of eluvial--deluvlal-proluvial origin and preserved rocks such as siltstones, argillite, shales, mealy dolomites, chalk, etc. Some low-strength soils can be placed in water [2].The graph (Fig. i) of the grain sizes of various earth structures constructed by this method shows curves bounding the region of suitability of soils as a function of the height of the fill layer and gives some characteristic grading curves of constructed dams [3].The soil of the first layer is placed pioneer-fashion in standing water of the filling area-pool formed by small embankments, whereupon the water being displaced flows over a spillway into the adjacent pool. After the pool is filled with soil, fill is placed in the next pool, etc. Then the second layer of the structure being constructed is place in the same way, etc.Initial compaction of the soil occurs under the effect of the soil layer's own weight and the dynamic action of the soil-loaded trucks Passing over the layer and bulldozers leve...
