Experimental collapsing of the slope of a 35-m embankment under the effect of seismic shooting was carried out at the construction site of the Nurek hydroelectric station for refining the characteristics of the mechanical properties of the soils.

The passage of major floods through incomplete large-scale high-head hydraulic facillties, and the scheduled development of stage construction of the reservoir as the structure is being raised, are serious engineering problems and require the timely completion of intake structures at each stage of construction. These circumstances were fully manifested during the passage of the Vakhsh flood in 1978 at the incomplete Nurek hydroelectric plant, in which the design head reaches 300 m and the maximum flood flows amount to 3600 mS/sec.Four intake tunnels arranged in stages according to reservoir depth were constructed in rock excavations on the left bank of the Nurek hydro project to pass the Vakhsh flows in 1978. The first three tunnels, I, If, and Ill, are construction tunnels, while the fourth is an operating h~h-flow spillway:with a deep intake. In addition to this, a similar spillway with a surface intake should be completed by 1980. The first four tunnels are accommodating high flows through the slope of the left bank, while the surface intake spillway is being excavated in the stage-Ill construction tunnel beyond the segmented-gate chamber (Fig. i).The stage I construction tunnel was intended for the passage of Vakhsh River flows during the initial period of construction of the hydroelectric plant. All remainln 8 tunnels would ensure filling of the reservoir after startup of the plantWs units, and for these purposes were equipped with segmented regulating gates designed for a capacity of 2000 mS/sec through two gates in each tunnel under a head of 100-120 m.Passage of maximum flood flows and the stepwlse impoundage in the reservoir during the construction period were to be provided for by the complete readiness of the next two tunnels --I and If, II and III, Ill and the deep spillway tunnel--by the next flood. Passage of flood flows during the plant's operation is provided for by two spillways and by the working units.The readiness of the basic structures of the Nurek plant in 1977 made it possible to maintain the level of the reservoir at an elevation of 858 m. This made possible the operation of the first six hydraulic units, of which three were equipped with temporary rotors designed for a reduced head with water supplied to them from a temporary intake.The complete readiness of the stage-III construction tunnel and the deep submerged spillway for passage of the 1978 flood and the further filling of the reservoir should have been provided by the planned constructlon schedule for 1978, and all units at the plant should be placed in service with basic rotors and water supplied from the permanent plant intake. In conformity with this, the total reservoir volume required to ensure the planned generation of electricity and to satisfy the demand for water in 1978 should be 8 kmS; this determined the required level of the reservoir--885 m.According to plan, passage of the 1978 flood and the impoundage of this volume of water in the reservoir should be realized in two stages:i. For water levels up to elevation 858 m...

An effective technology of constructing earth structures was developed and introduced on the construction of the flood-control complex of Leningrad, which after correlating to other local conditions can be successfully used in many other cases of hydrotechnical practice.The complex of structures, isolating the Neva Bay when catastrophic sea waves and storm winds approach from the Gulf of Finland and thereby protecting the city from destructive consequences of flooding, is located at a site between the populated aread of Gorskaya, Kronshtadt, and Bronka. The length of the route is 25.4 kln, including 22.2 km directly over the waters of the bay, with an average depth of the water of 2.9 m and height above the normal water level of 8 m [i]. Figure 1 shows the layout consisting of ii earth and rock dikes, two navigation structures, and six aqueducts. This complex, large, and diverse hydro developement consists of objects, structures, and mechanisms, many of which in such a combination do not have any analogues. The main characteristic consists in that the bulk of the construction and installation works is accounted for by the construction of the protective dikes, cofferdams, and other useful earth embankments. At present there are two variants of the technology of constructing dikes which differ in the location of the central and side zones, earth materials, and sequence of constructing (Fig. 2). In the first variant the central zone of the dike is constructed from fine sand and rests through transition zones against two rock berms preliminarily placed in water on a sand-~ravel bed. The sand is delivered to the field of operations by barges from underwater deposits in the Gulf of Finland. The rock and sand-~ravel soil is delivered by railroad from quarries of the Isthmus of Karelia over a distance of up to 150 km. The main shortcomings of this technology are the costly and labor-intensive delivery of scarce (under the given conditions) earth materials and impossibility of intensive opening up of the field of operations.On the suggestion of the general contractor -the Leningrad Trust for Specialized Hydraulic Engineering Works (Lengidroenergospetsstroi) -a second variant was developed on the basis of results of investigations by the B. E. Vedeneev All-Union Scientific-Research Institute of Hydraulic Engineering (VNIIG) and the Leningrad Branch of the All-Union Planning, Surveying, and Scientific-Research Institute (Lengidroproekt), which made it possible to start construction of the protective structures ahead of schedule, in 1981, since the use of imported earth materials was reduced to the minimum and local soils of nearby deposits were maximally used in it. In this variant of the dike the central zone is constructed of moraine loam of a crumb structure with an optimum particle-size distribution of the crumbs. Stability of the slopes of the loam embankment is provided by a rock revet/nent placed on a layer of sand~ravel soil. Construction of the structure begins with pioneer placement of loam in water to a depth up ...