Client: BM Holding
Total Installed Capacity 33 MW
High Pressure Power Tunnel
Steel Fiber Reinforced Concrete (SFRC)
Pressure Tunnel Lining with Drainage Holes
Arpa Hydropower Project is a diversion type hydroelectric facility that makes use of the head between 1005 m and 660.60 m of Arpa Creek for energy generation. The project is in operation since 2012.
The project consists of 1.670 m long open channel flow tunnel, octagon forebay, 100 m deep vertical shaft, 1.750 m long steel fiber reinforced lined energy tunnel, emergency valve chamber, 600 m long penstock inside the tunnel, 230 m long penstock outside the tunnel, powerhouse and tailrace channel. The type of water conveyance is designed as tunnel-shaft-pressurised tunnel, which minimizes the negative social impacts and the cost of project. The forebay which is located at a steep topography is designed as octagonal and linked with 100 m long vertical shaft from the center. This design reduced the amount of the excavation significantly. 282 m long access tunnel connecting to the intersection of shaft and pressurized tunnel has been designed for reducing the construction time of pressurized tunnel by executing the excavation works through two faces simultaneously. A watertight gate that can sustain 100 m of water pressure was placed at the intersection of shaft and energy tunnel and also can be used for maintenance purposes during operation.
Cost Effective Solution in Pressure Tunnel
The tunnel was required to be lined due to the hydraulic and geological requirements. Steel fiber reinforced concrete has been used in the horseshoe-shaped tunnel, which eliminates the use of reinforcement, shortened the construction process, reduced the cost and increased the durability of the tunnel. At the locations where the hydrostatic pressures reach around 300 m and the rock mass over the tunnel cannot resist this pressure, steel penstock which is fixed by support masses have been employed. Considering that the system is pressurized and the considerable volume of water accumulated in the tunnels, an emergency valve was constructed in the tunnel.