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Dongjiang HPP

Dongjiang HPP, located at Zixing City of Hunan Province, 45km away from Chenzhou City, is the fourth cascade development on the Leishui River. The dam is of double-curvature thin arch type, 157m high, and was the highest double-curvature arch dam at that time. The project has an installed capacity of 500MW and was awarded national gold prizes for excellent engineering investigation and for excellent engineering design.
The project is mainly for power generation and concurrently for flood control, navigation, and industrial water supply. It features in a reservoir NPL of 285m, a total storage of 9.565 billion m3, and an annual energy output of 1,230 GWh. The project was commenced in March 1978, the first unit was put into service in October 1987, and all the three units were put into operation in August 1989.
Main Technical Features:
(1) Design of high concrete double-curvature thin arch dam. Dongjiang dam was the first high double-curvature thin arch dam built in China at that time. The dam is a double-curvature arch dam with variable circle center and variable radius, the maximum circular arc radius 309.3m, maximum central angle 95°, dam crest arc length 438m, crest width 7m, maximum bottom width 35m, maximum height 157m, and thickness-height ratio 0.223. To improve the stress status of arch abutment, the downstream surface of equal-thickness arch ring was thickened locally, and the horizontal arch ring was modified to an arch with variable thickness. Gravity abutments were furnished above El. 270m on the right bank. The design ranked the country’s leading level in 1980s.
(2) Slit flip bucket energy dissipater with its own characteristics was adopted for the right-bank ski-jump spillway.
(3) An arrangement manner with penstock on downstream face of the dam was adopted for the first time in China. The penstock was 5.2m in diameter and was encased with reinforced concrete.
(4) The project was designed with the largest eccentric hinge radical gate in the world, dimensions 6.4m7.5m and maximum retaining head 120m.
(5) New technologies employed in construction include three-side presplit blasting in dam foundation excavation and thermal insulating coverings and double air cushion plastic membranes for concrete surface protection. Thermal insulating coverings were made by putting from granular polystyrene foamed plastic into woven bags and were put up on transverse joints or upstream/downstream surface by dowels. Double air cushion plastic membranes, made by superimposing two layers of plastic membranes with bubble, were pasted on formwork in advance or on concrete surface right after form removal.