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Wuqiangxi HPP, located in Yuanling County of Hunan Province and 300km away from provincial capital Changsha City, is the largest power station on the main stream of the Yuanshui River. It has a gravity dam (maximum height 85.83m) and an installed capacity of 1200MW. It 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 and navigation. It features in a NPL of 108.00m, a total storage of 4.35 billion m3, a check water level of 114.7m (P=0.01%), a total discharge flow of 54,000m3/s, an installed capacity of 1200MW. The construction of main works was commenced in December 1989, and all the five units were put into operation in December 1996.
Main Technical Features:
(1) Because of the narrow river channel, its powerhouse at dam toe, flood discharge and energy dissipation structure and navigation structure were arranged in one row, of which the flood discharge and energy dissipation structure occupied a large part of the river channel. How to minimize the length of overflow front and work quantity and to ensure the safe operation at check water level 114.7m (P=0.01%) and total discharge flow 54,000m3/s was a key problem to tackle in project layout. With cooperation of the companies concerned, HydroChina ZhongNan adopted an energy dissipater scheme combining flaring pier, ski-jump bottom outlet and stilling basin based on plenty of experimental studies. Compared to the scheme proposed in the preliminary design, the scheme adopted reduced the length of overflow front by 24m and the length of stilling basin by 50m. That not only solved the layout problem, but also saved the excavation volume by 1.10 million m3 and concrete volume by 40,000 m3.
(2) Giant radial gates for surface orifices largest in the world in the 20th century were employed, sized at 19m23m (WH).
(3) Large-tonnage prestressed gate pier structure was applied successfully.
(4) The head of its continuous three-lift ship lock was the highest in China in the 20th century, the service head of single lift 42.50m.
(5) Large-diameter penstock on downstream face of the dam was used, with a diameter up to 11.2m.
(6) The utilization of temporary ship lock successfully solved the problem of navigation during the construction period.
(7) The new technology of continuous large-area thin-lift concrete placement for dam body was first adopted in dam concreting to shorten construction period.
(8) Left-bank high slope was treated successfully, and the stability problem of creeping high slope was solved.
(9) 8.3m-diameter large-runner turbines were employed.
The project is mainly for power generation and concurrently for flood control and navigation. The power station is connected to Central China Grid and mainly supplies power to Hunan Province. The catchment area above the dam site is 83,800km2, accounting for 93% of the whole Yuanshui basin area. At the dam site the mean annual flow is 2,050m3/s, annual runoff 64.3 billion m3, and measured maximum flood discharge 27,000m3/s. The formation of the dam area is mainly of sandstone, quartzite, slate and phyllitic slate, with a mean wet compressive strength of 569～2160kg/cm2. The strata strike parallel to the river and dip to the right bank. Its reservoir is a seasonal regulation one and has a NPL of 108m and a total storage of 4.2 billion m3.
Many new technologies and materials were adopted in the design and construction of the project, including new energy dissipater combining flaring pier, ski-jump bottom outlet and stilling basin, surface bay, large radial gate, large-diameter penstock, stainless steel runner for large unit, continuous large-area thin-lift concrete placement, high slope, high-head three-lift ship lock, and large-scale aggregate processing system, which were supreme in China and represented the hydropower construction level of China in 1990s.