The Zeya hydropower scheme is under construction in the middle reach of the Zcya River, a large tributary of the Amur River [1]. Included in the structures are a massive buttress dam with a spillway section, a power-station unit with a building adjoining the dam, distribution works and auxiliary operational structures, a permanent bridge over the Zeya River, and a transshipment port. Selection of Type of Concrete DamConsideration was given to gravity, massive buttress, and multiple-arch forms of concrete dams. The selection of type of concrete dam for severe climatic conditions is a complex engineering problem. An analysis was made of the construction and operation experience with the dams of the Bratsk, Mamakan and other hydropower schemes, construc~d under similar climatic conditions [2][3][4][5][6]. Full-scale observations of these dams and computations showed that the behavior and strength of a dam is most greatly affected by the forces due to external temperatures. It was necessary to select a dam of such design that it would be able to adapt itself to normal and continuous operation at a below-zero mean annual temperature and for a considerable air-temperature variation during the year. Semigravity dams with internal cavities (dams with widened joints, and massive buttress types) have this advantage, which make it possible to artificially create a required temperature regime within the dam body, both during the construction period and in service.Computations for the Zeya hydropower scheme and operational experience for the Mamakan dam have shown that this type of dam, with enclosed cavities, provides the maximum monolithicity of the structure, the minimal widening of construction joints along the periphery, an above-zero concrete temperature in the principal load-carrying components, operational stability of the drainage system, and a guarantee that the design distribution of foundation pressures will be achieved. The above considerations led to the decision to design the Zeya dam in the buttress form, with an internal artificial climate, maintained in enclosed and heated cavities.For a mass-gravity dam it would be necessary to take supplementary measures to reduce the thermal effects on its stressed state. Consideration was given to one such measure, the use of thermal insulation along its downstream boundary. However, this was not feasible at the spillway boundary. Therefore, an alternative which is the principal method for gravity dams was examined, namely, the provision of thermal protection and heating in the downstream boundary zone. This solution would be more effective than the former but would entail considerable operating expenditure.Adoption of the massive-buttress alternative for the Zeya dam not only reduced on the unfavorable thermal forces included in the dam's stressed state but also enabled its cost to be lowered 15% below that of a gravity-profile dam. Under very severe climatic conditions the massive-buttress type is superior to the mass-gravity dam, not only from the viewpoint of ensurin...
Construction of the Zeya hydraulic development was started in 1964. the river channel was closed off in 1972, and the first generating unit, with an installed capacity of 215,000 kW, was placed in operation in November 1975. The startup complex Included the following structures: the first stage of the massive buttress dam, two powerhouse sections together with the erection area, the central control desk, the transformer shop, the 220-kV switchyard together with the switchboard block and the compressor room, the trans-shippiag port. and the bridge across the Zeya River.The first start'up scheme for the units of the Zeya plant was worked out during the technical project stage. The periods for commissioning the units and readying the upstream front ( Fig. 1) were adopted on the basis of overall completion of the hydraulic development in 1978. It was assumed that during the first years the reservoir would be filled with an inflow having a 50% frequency of occurrence. The reduced construction ~rne (completion three years after commissioning the first units) and the rapid filing of the reservoir dictated large capital Investments (about 80%), which were necessary for commissioning the ~rst units. Subsequently, other alternatives were considered for placing the first units in operation with lower capital investments. The reduction in the volumes of the startup complex took place in three stages (1971, 1972, and 1973), in each of which optimal solutions compatible with the construction progress were found. The problem of the teehnieoeconomic indices of the startup complex for the first units was solved as part of the general startup scheme for all units, since the solution of this problem only within the limits of the minimal capital investments for commissioning the first units could lead to delays in commissioning the next units or to deterioration of the power-economy indices of the starmp period.The reduction in the capital investments for commissioning the first units was accomplished by the following means: a) Lowering of the startup head. The Francis turbines designed for the project could operate under a head of no less than 50 m" according to factory requirements, for this reason it was necessary to install in the first units temporary runners to be replaced by permanent runners, or to install diagonal turbines, capable of operating under heads of 40-35 m. The technicoeconomic analyses showed the expediency of the use of diagonal turbines. b) Limiting the rate of reservoir filling during the first years within the range of inflows having a 95% frequency. c) S tarring reservoir filling in the second half of the summer with a view to reducing the available storage for receiving the design storm flow. d) Making a detailed analysis of the dam behavior during the different construction stages in order to determine the sequence in dam construction and grouting for maximum reduction in the startup concrete volume while adhering to the minimum allowable stresses at the dam foundation level in the concrete on the upstrea...
The site of the Zeya hydroelectric station is located in a gorge whose width at the water's edge is 350 m. The mean annual air temperature in the region of the construction site is --4.1~ the mean monthly temperature of the warmest month (July) is +18.6~ and of the coldest month (January) --30.1"C.The mean annual temperature during construction of the main structures varied from +0.4 to --2.5 ~ .An intrusive mass of dlorltes serves as the foundation of the structures of the hydrostation. The diorites are intersected by several zones of tectonic disturbances with a thickness from 0.2 to 3 m.The modulus of deformations of the foundation varies from 3-10" to 2.104 MPa and averages 1.3.104 MPa. The indices of the shear strength of the concrete with respect to the dlorites are: friction coefficient 0.70 and cohesion 0.03 MPa. The specific water absorption of the rocks is from 0.01 to 0.005 dmS/mln (in rare cases it was 1 dm'/mln~.The barrier of the Zeya hydrostation is formed by a buttress dam with a crest length of 714 m and maximum height of l12 m. The volume of concrete in the dam is 2,160,000 m'. The dam has a triangular profile with upstream and downstream slopes of, res~ectlvely, 1:0.15 and 1:0.8.The buttresses with a 7 m thickness on the spillway part and 5 m on the powerhouse part on the upstream side have massive heads.The thickness of the head varies with height from ii to 6 m. On the downstream side the hollows between the buttresses are covered with 3.5-m-thick slabs on the spillway part and 1.5-m-thick slabs on the nonoverflow parts [i]. The width of the spillway section is.15 m and of the powerhouse section 24 m.
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