Dukouba Hydropower Station Dam Civil works Construction organization design document
Dukouba Hydropower Station is a hybrid power station located in the upper reaches of Meixi River, Xinzheng Township, Fengjie County, Chongqing. It is the first level of cascade planning of Meixi River. The dam site area controls a drainage area of 765km2, with an average annual flow of 18.2m3/s. The power station is a Grade III medium-sized project mainly for power generation, with comprehensive benefits such as tourism and flood control. The total storage capacity of the reservoir is 98.54 million m3, and the effective storage capacity is 70.11 million m, which is an annual regulation reservoir. The dam site is located 7km upstream of Xinzheng Township, Fengjie County, 90km away from Fengjie County; The plant is located at the Dalangou of Pingping Town, 54km away from Fengjie County. The main structures of Dukouba Hydropower Station include water retaining (discharging) structures, water intake structures, diversion structures and power house, with a total installed capacity of 129MW (2 × 64.5MW). Concrete arch dam is a Grade 3 building. The foundation surface elevation is ▽ 470.00m, the dam crest elevation is ▽ 578.50m, and the maximum dam height is 108.5m. Parabolic variable thickness double curvature arch dam is adopted for its shape. The center angle of the crown is 98 °, the maximum half center angle is 46.76 °, and the minimum half center angle is 26.88 °. The maximum radius of curvature of the arch ring center line at the crown beam is 120.6m, the minimum radius of curvature is 53.4m, and the dam axis is 284.123m long. It is divided into 16 dam sections. The dam crest is 4.5m thick, the bottom is 20.0m thick, and the thickness height ratio is 0.18. Grouting gallery, traffic gallery, sump, pump and vent pipe are set inside the dam body, and grouting adit, drainage tunnel, traffic bridge, dam rear bridge and elevator shaft are set outside the dam. The flood discharge structure is located in the middle of the dam. The center line of the overflow weir coincides with the center line of the dam. It is composed of three overflow surface holes with the size of 12m × 12m (width × height). Each hole is equipped with an arc working gate for control, which is opened and closed by a hydraulic hoist. Weir body adopts WES type weir surface curve, and weir top elevation ▽ 563.00m. The front of weir crest adopts 1/4 elliptic curve, the rear of weir crest adopts curve equation, and the outlet adopts downflow. The maximum discharge is 3840m3/s, and the corresponding unit width flow is 116.4m3/s · m. As an energy dissipation structure, the plunge pool is a Grade 3 structure, including plunge pool, secondary dam and apron. The plunge pool is stepped, 165.53m long, 44m wide at the bottom, 79.44m wide at the top, and 469.0m at the lowest bottom elevation. At the end of the plunge pool, there are two dams with high backwater level. The axis is 66m long, 17.5m high, 2.7m wide at the top, 27.2m wide at the bottom, and ▽ 474.5m high at the bottom. There are drainage galleries and pumps in the dam. Behind the two dams, there is a 20m long apron and a toothed wall. The water intake adopts the tower type, which is divided into the upper structure and the lower structure. The substructure includes the water inlet passage, trash rack, trash rack breast wall and bulkhead gate shaft; The upper structure includes the water intake operation and maintenance platform, trash rack hoist chamber, hoist working bridge, bulkhead gate hoist chamber and traffic bridge. The elevation of water inlet bottom plate is ▽ 525.80m, and the elevation of maintenance platform is ▽ 578.50m. The headrace tunnel is arranged along the left bank, 600m long, round, 4.2m in diameter, and is lined with full section concrete. The cofferdam type is overflow cofferdam at the upstream and overflow cofferdam at the downstream. The upstream cofferdam shall be constructed by throwing and filling rubble revetment on the upstream face, reinforcing bar gabion slope pressing on the downstream face and anti-seepage with C20 concrete face slab. The downstream cofferdam is filled with earth and stone, and the structure of composite geomembrane seepage prevention is adopted. In order to meet the needs of mechanical construction, flood control and rescue, traffic and slag removal, the top width of upstream and downstream cofferdams is 8.0m. The upstream cofferdam is 14.4m high, the weir top elevation is ▽ 496.70m, and the axis length is 72.15m. The downstream cofferdam is 6.5m high, the weir top elevation is ▽ 486.80m, and the axis length is 31.3m. The diversion bottom outlet is constructed and blocked, and the diversion tunnel is blocked. The two diversion bottom outlets are arranged on the 8 # and 9 # dam monoliths. The elevation of the bottom outlets is 486.40m, and the size of the bottom outlets is 7m × 7m. The bottom outlets need to be plugged finally. The diversion tunnel is blocked with a gate for temporary water retaining, and the length of the plug is 36m. The construction diversion and water flow control works include river closure, drainage, construction of diversion bottom outlet, preparation of diversion bottom outlet and diversion tunnel plugging, flood control and other works, as well as other relevant temporary works. 1.2 Main contract items and quantities Main contract items include: concrete arch dam works, plunge pool works, water intake works, tunnel works. See the following table for main quantities. The construction period of Dukouba Junction Project is scheduled to start in the middle of July 2007, and the main works will be completed on June 1, 2010. Table 1-2 Main Control Duration