Rogun dam is a 335m high clay core rockfill dam which will be constructed on Vakhsh River in Tajikistan. Originally, two diversion tunnels with similar geometry were designed for discharging the seasonal floods, up to 3290m3/s. River diversion was carried out in November 1987 and a 45m high rockfill cofferdam was constructed. However, because of two collapses in the diversion tunnels, the cofferdam was overtopped in May 1993. Reconstruction of these tunnels started in 2009 and the collapsed areas were repaired. Nowadays, the design of complementary rehabilitation including new concrete lining for those parts of the tunnels will be used as tailrace tunnels are underway. The present paper describes the present conditions of diversion tunnels No. 1 and 2, explains the procedure used for the structural design of these tunnels, and presents the results of such design.
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