Main structures of Zeya hydropower scheme

Abstract

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...