The concrete aggregate is processed from a quarry. The designed production capacity of the sand and gravel processing plant is1000t/h, the maximum concrete gradation is 4, and the coarse aggregate is divided into 4.8 ~ 19~38mm, 19~38mm, 38 ~ 76mm and 76 ~1. Fine aggregate is divided into 4.8 ~ 1.2 mm coarse sand and 1.2 ~ 0.74 mm fine sand. Two 4× 4.5m3 mixing plants produced by Italy CIFA Company, each with a production capacity of 360m3/h. The pre-cooling capacity is 8.3 million kcal/h, and the storage temperature of dam concrete is not higher than1h. For concrete pouring, three 30t radial cable cranes are used to hoist the concrete into the silo. The span of the cable crane is1265m, the horizontal speed is 7.5m/s, the vertical speed is 3m/s ... the tank lifting capacity is 9m3/s, and the longitudinal slope of the rail at the moving end of the cable crane can be set according to the terrain conditions, with the maximum longitudinal slope of 19%. The actual excavation amount of dam foundation is 2.88 million cubic meters, and the highest excavation intensity is194,000 cubic meters/month. The height of the steps is10m. AtlasRoc742HC-0 1 drilling rig bore holes with diameters of 76mm and 89mm, and the hole spacing was mostly between 2.5 m ×2.5 m and 2 m ×2 m, using 60mm emulsion explosive coils, and the hole plugging depth was 0.8 ~ 2 m ... The underground powerhouse construction belongs to the excavation of large chambers and high side walls. The surrounding rock is hard and complete, with little groundwater, but high in-situ stress. The maximum principal stress in syenite is 20 ~ 30 ~ 40 MPa, and that in basalt is 30 ~ 40 MPa. In the process of excavation, in addition to reasonably arranging the excavation sequence and slag discharge channels of each cavern and strengthening the monitoring of surrounding rock deformation, a large number of1.75t prestressed anchor cables are used in the powerhouse, main transformer room and tailrace surge chamber, and steel fiber shotcrete is adopted in time according to the geological forecast in areas where rockburst may occur.
For the excavation of inclined shaft (37 58') and 9 vertical shafts (deepest 186m) of high-voltage cable, a drift pilot shaft with a diameter of 1.5m is drilled by a patio drill, and then the conventional expanding excavation method is adopted from top to bottom. The hole inclination is low, the bottom inclination of the 280m inclined hole is less than 20cm, and the actual productivity reaches 0.5 ~ 0.7m/h..
The surrounding rock geological conditions of the two diversion tunnels are also good. The main engineering geological problems are: two soft rock zones (fissure chlorite basalt, chlorite basalt and actinolite basalt), the fracture zone between syenite and basalt, and rockburst caused by high ground stress. The maximum principal stress of in-situ stress is 20 ~ 35 MPa, and the direction of action is basically perpendicular to the river and inclined to the river bed, with an inclination of about 10 ~ 30. The main excavation method of diversion tunnel is drilling and blasting. At first, random bolts and local sprayed concrete are generally used for support, and finally, systematic bolts, sprayed concrete and local reinforced concrete lining are used for support. In order to meet the requirements of high-speed water flow and wood flow, the side wall and floor are lined with reinforced concrete thin lining. Ertan Hydropower Station is equipped with six parallel diversion pipes, which are arranged by single pipe and single machine. The length of each pressure pipeline varies from 302 meters to 368 meters, and the inner diameter of the pipeline is 9.0 meters. The lower bending section and the lower horizontal section of the pressure pipeline are pressure steel pipes, and the steel pipe near the factory building is connected with the volute through the inner diameter of the gradual change section of 9.0m to 7.2m.. The main structures and lengths of the six pressure pipes are the same.
The pressure pipeline is buried underground and is designed to be supported by concrete, rock and steel lining. The designed maximum water head is189.0m. The main material of pressure pipeline is ASTM A 537 CL. 1 steel.
Each pressure pipe consists of 39 parts. Calculated from the center line of the pressure pipes, the total length of the six pressure pipes is 599.964 meters, the weight of * * * is about 5383 tons, and the wall thickness of the pressure pipes is 28 mm to 52 mm.
The underground powerhouse project of Ertan Power Station was undertaken by Sino-German joint venture SGEJV, with Germany and Holzman as the responsible parties. The pressure pipeline project is a part of the underground powerhouse project contract. Except for the second-stage concrete backfilling and grouting work outside the pressure pipeline, the whole pressure pipeline project is subcontracted to NOELL Company of Germany. NOELL company is supervised by SGEJV, and the instructions of engineers are conveyed by SGEJV. The pressure pipeline project started in September 1994 and was completed in February 1997.