Dynamics of the formation of an ice prism on reservoir slopes of a pumped-storage station

Abstract

When designing sloping structures on reservoirs with carryover and seasonal regulation of streamflow, the character and types of action of ice are determined in conformity with the Cons=ructlon Specifications and Regulations SNiP 11-57-75 [6]. There are no such regulations for reservoirs with daily regulation of the volume and level of water owing to lack of knowledge about the conditions and process of ice formation in these reservoirs and its physical and mechanical properties [1][2][3][4][5][6].The on-site investigations being conducted at the Kiev pumped-storage station (PSS) include observations of the state of the dike slopes of the PSS reservoir, weather conditions, and wind-wave and ice regimes.This article presents the results of these observations and the relationships following from them, which are of interest in connection with the possibility of taking them into account when designing structures situated under similar conditions.In this case it is taken into consideration that no slope disturbances were detected during the period of observations from 1975 to 1980.The ice situation in the Kiev PSS reservoir, which is operated in a daily regime, during the period of negative temperatures has the following characteristics according to the onsite observations [3]: a cover of solid ice forms in the middle part of the reservoir; prisms of multilayered ice frozen to the slope form on the upstream slope of the dike along the water edge at the normal pool level (NPL); between them is a polynya (clearing) with fragmented ice floes (Fig. i).The multilayered ice prism on the slope has the shape of a triangle, top width to I i = 12-14 m, thickness at the slope to h i = 3.0-3.5 m, and volume to W i = 18-24 m 3 per meter of dike length.The structure of the ice is not homogeneous and three characteristic zones are noted in the cross section of the prism.The ice of the upper zone is amorphous, layered, and white. The thickness of the layers is 5-15 mm and the interlayers between the layers (up to 5 mm) are filled with snow. The ice of this zone forms due to water of the reservoir while standing at the NPL and precipitation.The ice of the middle zone is of a cloudy color, semicrystalline with air bubbles of diameter d ~ i0 mm, with vertical cracks of various depths, sometimes with snow inclusions.In the lower zone the ice is crystalline with air bubbles of diameter d s 5 mm and transparent.Individual cavities are found in =he lower part of the prism. With a total measured ice prism thickness of 1.40 m, the thickness of the upper, middle, and lower zones were, respectively 15, 45, and 80 cm.

Ice Regime for Basins and Pumped-Storage Facilities

“…More than 220 pumped-storage power plants (PSPP) have been built up to present days [1][2][3][4][5][6][7][8][9][10][11][12][13][14], and a lot of them still operate under cold winter conditions.…”