River closure construction of Nuozhadu hydropower project
OU Shun-li · Yangtze River · 2008
Nuozhadu hydropower station is a large I project and its main permanent hydraulic structure is grade I structure.The project is composed of core wall type rockfill dam,flood spillway on left bank,flood discharge tunnels on left bank and right bank,underground power generation system and diversion works on left bank etc.The reservoir capacity is 23.703 billion m3,the installed capacity of the power station is 5850 MW(9×650MW).In river closure of Nuozhadu hydropower station,the measured maximum flow velocity at closure gap was 9.02 m/s,the maximum water level difference before closure was 7.16 m,the maximum discharge was 2890 m3/s.For the reason of sufficient preparation,reasonable arrangement, the river closure characterized with large water level drop,large discharge,high flow velocity and difficulty was completed safely and orderly.The experiences obtained in this river closure are: ① it is very important for river closure to keep abreast of flow condition and reasonably select river closure time;② One-off success of river closure depends on full preparation,scientific and reasonable advancing construction,decision on-site commanding;③reasonably design of berme dyke advance;④ the berme dyke advancing with proper upper and lower spur angles is feasible to form stagnant area and favourable for river closure with large discharge and flow velocity;the berme dyke head should be protected timely and should not be too far from axis,if it exceeds 10 m,the scoured place should be dumped again.