Dams, hydroelectric power plants
Government of Tajikistan
Start Date
In progress

The Rogun Hydropower Plant, on the Vakhsh river in Tajikistan, is designed with an installed power of 3’600 MW to provide additional energy supply for Tajikistan and neighbors countries.

The design of the tunnels for the protection against flood, during the various phases of the project implementation and along the operation period, is a challenge in consideration of the risk of overtopping of the rockfill dam and due the fact that the dam location is placed in a seismically active zone; i.e. several important faults cross the tunnel profiles, requiring ad hoc design of relevant linings.

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Detailed Overview

Project Highlights

• Rockfill Dam ( with impervious earth-fill core type, H = 335 m, L_crest = 650 m, V = 70 Mm³ )
• Cofferdam (raising of existing 50 m up to 100 m )
• Reservoir ( full capacity = 13’3000 hm³ )
• Diversion Tunnels ( No. 3, Q_tot = 5’600 m³/s )
• Spillway ( No. 5 tunnels, D = 9-15 m, Ltot = 10 km, Q_tot = 7’800 m³/s )
• Power waterways and tailrace tunnels
• Underground power station ( No. 6 Francis turbines, IP = 6×600 MW )

The Rogun project was commenced in the sixties, within the U.R.S.S., and its design and construction evolved until now. The dam type is an impervious core rockfill dam, deemed the most adequate type for the specificity of the site and the size of the dam.

The dam construction is phased in several construction steps: pre-cofferdam (used to start the river diversion), cofferdam (starting for early generation, crest el. 1’065 m a.s.l.), Stage 1 dam (increasing of early generation, crest el. 1’110 m a.s.l.) and Main dam (final crest el. 1’300 m a.s.l.).

Two Diversion Tunnels, named DT1 and DT2, developed in parallel with their intakes were placed shortly upstream of the pre-cofferdam on the left bank, while a third tunnel at the right bank, named DT3, is foreseen at higher elevation to complement the discharge capacity of the above-mentioned tunnels.

Two Middle Level Outlet are foreseen: MLO1 and MLO2.
MLO1 will operate during construction and is divided into two stretches. The first one is a single 15 m diameter conduit, with reinforced concrete lining, and a gates chamber. When the reservoir will reach the final operation level, the gates will definitely be closed and this portion of the tunnel will be abandoned. The second stretch includes a bifurcation that splits the tunnel into two steel lined tunnels (Left and Right) of a smaller diameter (9 m). This second portion will be used during plant operation, fed by two upper shafts, S1 and S2. The MLO2 engages on the DT3 after the gates chamber, from a higher elevation.

There are also two further tunnels on the right bank, acting as High-Level Tunnel Spillways. They were conceived to replace the high-level orifice and surface spillways of the original project. The two tunnels with an internal diameter of 9 m, are entirely steel lined and equipped with an inlet shaft structure (named respectively S3 and S4). These spillways will discharge an exceptional flow of about QPMF = 9’000 m3/s. Their exceptional size and the need to cross important faults along their path make the design of these tunnels also very delicate and stimulating.

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