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Zhexi HPP, located at Anhua County of Hunan Province, has a 104m-high concrete massive-buttress dam and an installed capacity of 947.5MW (including extension). It is mainly for power generation and concurrently for flood control and navigation. It feeds power to Dongting Lake and Central Hunan industrial areas via 110kV and 220kV transmission lines and is a backbone power source of Central Hunan power grid. It is honored as the first ruby of Hunan.
The dam site is located in a V-shaped valley, wher_e mountains stand facing each other and the peaks are about 200m high above the normal water surface. The dam foundation is interbedding of slightly metamorphic sandstone and slate of Banxi group of presinisan system. The rocks are compact and solid, with high compressive and shearing strength and low permeability, and are thin and have high dip angle although there are interlayer offset fracture zones. Thus these fracture zones would not impact the dam building.
A scheme of hollow gravity dam plus river-side powerhouse was adopted for the project layout. The main structures are the dam, right-bank conduit-type surface powerhouse and left-bank navigation structure. The dam consists of single-buttress dam for the overflow dam section and slotted gravity dam for the non-overflow section, and slotted step contracted flip bucket ski-jump energy dissipation was employed. The surface powerhouse accommodates one 72.5 MW unit and five 75 MW units, one penstock for one unit. The navigation structure is a slope dry hauling logway, accessible for 30t-level ship, with annual goods transported through the dam up to 250,000 tons.
The project was constructed by Zhexi Hydropower Station Engineering Bureau. The first unit was put into operation on January 28, 1962, and the rest were put into service in April 1965, April 1966, May 1968, October 1971, and July 1975, respectively. The navigation structure was completed and put into service in 1977.