Effective fastening of the bottom of the stilling basin of a high-head dam by prestressed anchors

Abstract

1. The problem of energy dissipation of the flow remains one of the most important in constructing high-head hydraulic structures with pulsating loads. 2. During operation of the world's largest gravity-arch dam of the Sayano-Shushenskoe hydrostation, the energy of the flow being discharged is dissipated by a stilling basin. It was established that the powerful dynamic impulses created in this case originate, among others, from the baffle platform and its foundation. The latter circumstance requires the provision of reliable tightness of the joints between the blocks composing the platform and deep solid transition of the platform with its foundation. 3. For the first time in domestic hydrotechnical practice fastening of the platform of the stilling basin by means of advance grouting and prestressed anchors installed to a depth greater than 20 m was mastered on the construction of the Sayano-Shushenskoe dam. 4. Works on the manufacture, transport, assembly, tensioning, and testing PSAs were successfully mastered by the Krasnoyarsk enterprise of Gidrospetsstroi. A number of innovations were introduced at the know-how level. 5. Passage of the 1992 floodwaters at the elevation of the NPL, after pumping water from the stilling basin, showed the effectiveness of the repair and restoration measures taken, which indicates the correctness of the selected designs, optimal technology, and high quality of the works of Gidrospetsstroi. 6. An analysis of the strengthening works for high-head structures under analogous conditions permits recommending the following measures for designing and constructing a stilling basin: grouting of the foundation in the region of the stilling basin to a depth of 30–40 m; grouting of the joints through embedded grouting reinforcement between the blocks of the platform of the stilling basin and other places of it; construction of relief drainage; advance grouting of boreholes and installation of prestressed anchors to a depth of 20–25 m. The indicated measures increase the operating reliability of the stilling basin and prevent the possibility of destruction of its concrete structures.