Lining pouring of No. 1 tailrace tunnel of Kaikai Hydropower Station in Angola completed ahead of schedule

China News Service, Kunming, September 30 (Huangdi) China Energy Construction Gezhouba Group reported on September 30 that the lining concrete pouring of the tailrace tunnel No. 1, a key line and control project of the Angola Kaikai Hydropower Station project undertaken by the group, was completed 77 days ahead of schedule, marking that the tunnel has fully entered the consolidation grouting and ancillary engineering construction stage.

Kaikai Hydropower Station is located in Dondo City, Kwanza Norte Province, Angola. It is located in the middle section of the Kwanza River, the "mother river" of Angola. It is the third level of the eight-level cascade hydropower station in the basin. The power station has a total installed capacity of 2,172 MW, and the average annual power generation after completion will reach 8,566 GWh. It will meet more than 40% of Angola’s power supply needs, provide more than 6,000 local jobs during the peak construction period, and promote local economic and social development.

As an important part of the water delivery system of Kaikai Hydropower Station, the tailrace tunnel is connected to the tailrace pressure regulating chamber and externally to the Kwanza River. It assumes the core functions of transporting water flow and discharging the tailwater of the generating unit. The tailrace tunnel is divided into No. 1 and No. 2 holes. The two holes are arranged in parallel. The axis of the tunnel is 50 meters apart. The length of the tunnel is 5151.329 meters and 5179.469 meters respectively. Due to the large span, deep burial depth and long distance of the cavern, the lining construction has the characteristics of limited working space, frequent intersection of processes, and large amount of concrete pouring.

Since the opening of the first warehouse for concrete pouring, the tailrace tunnel construction team has scientifically coordinated the allocation of core resources of four types of trolleys: inverts, steel bars, linings, and grouting, and built an efficient production line with "inverts operating first, steel bars following simultaneously, linings in place accurately, and grouting seamlessly relaying." The project team also dynamically optimized the trolley transfer, positioning and disassembly processes to minimize non-operation time and strictly controlled the construction period of a single warehouse within 5 days to achieve interlocking and efficient connection of various processes.

During the construction of the project, the construction team implemented full-process monitoring of key parameters such as steel bar binding spacing, protective layer thickness, formwork flatness and stiffness, concrete mix ratio, slump and pouring vibration. Quality personnel work 24 hours a day, and rely on a digital and intelligent management and control platform to establish a traceability mechanism for the entire life cycle of quality issues. After testing, the size and appearance quality of the 371.6-meter lining completed this time met the design and specification requirements.

In order to ensure construction safety, in view of the complicated working conditions with intertwined risks such as high-altitude operations, hoisting, temporary power use, and vehicle traffic in the cave, the project department prepared special construction plans and emergency plans one by one, and continued to optimize the ventilation, lighting, and drainage operating conditions in the cave to achieve zero accidents in safe production throughout the entire cycle.

In the next step, the project team will steadily promote follow-up construction such as the consolidation grouting of the tailrace tunnel, the concrete pouring of the No. 2 tailrace tunnel lining, and the tailrace outlet.