Investigation of the causes of destruction of the separators of a ski-jump spillway of a high dam

Conclusions

For the first time the method use for investigating flow separators of high-head structures made it possible to recreate on a model cavitation phenomena that occurred in the original. The studies established the main cause of destruction of the elements of separators. The sources of cavitation that involved destruction of the concrete on the surface of the separators are: the presence of a sharp edge at the junction of the top and side surfaces of the separator; the presence of a poorly streamlined section at the initial part of the separator at the junction of the vertical side faces and surface of the spillway at the entrance to the gap between the separators; the presence of construction defects on the surfaces of the separator (depressions, pits, beds, and, especially, projections from formwork offsets). The last, as the experiments showed, are the most dangerous, especially if their vertical face is oriented against the flow.

Rounding of the edges can eliminate the occurrence of cavitation on the side surface at the start of the separators; however, the requirements imposed on the quality surfaces remain the same, since this does not eliminate cavitation on irregularities.

Facing of the separators and adjacent spillway surfaces with metal provides sufficient smoothness and greatly increases the resistance of the surface to cavitation erosion. Here one can consider that the lining practically eliminates the appearance of concealed but probable defects on the concrete surfaces during operation of the structures.