First-stage cofferdams for the construction of the sayano-shushensk hydroelectric station: Fid-Bau Portal

First-stage cofferdams for the construction of the sayano-shushensk hydroelectric station

Korol', S. I. / Kazakevich, N. G.

Conclusions 1. In the construction of the Sayano-Shushensk hydroelectric station, most of the volume of the first-stage earth cofferdams was placed in the dewatered excavation bay, which was protected by a low-water cofferdam placed along the outer perimeter of the main cofferdams. The cofferdam works were carried out successfully. This method of cofferdam construction can be applied at other sites also, where the low-water period in the river is long. With this method, an earlier development of the excavation bay is achieved, and a good standard of connection between the cofferdams and the rock foundation is obtained. 2. The experience at the Sayano-Shushensk hydroelectric station shows that it is possible to construct a longitudinal earth cofferdam, for velocities in the constriction ranging up to 10 m/sec. This achieves a significant economy in comparison with a cribwork cofferdam. 3. When constructing cofferdams, where fill layers are frozen, the cofferdam body remains in the frozen condition for several seasons. In such a case, should the cofferdam settle irregularly and be undercut, no selfsealing of the core deformations occurs, and arching may develop. Therefore, to ensure normal performance of the cofferdams, and to prevent the formation of points of concentrated leakage, the supporting gravel zones must be maintained without fail. Even during the low-water period, when design indicates that the full section of the cofferdam is not required, a deep undercutting of its slope is not permissible.