No 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.

For different types of drainage arrangements, use is basically made of multilayer sand-gravel and rubble inverted filters, the construction of which is extremely difficult and costly. A considerable portion of the total volume of the required sand and rubble is used for filters under the upstream slopes of large earth dams.The increasing volume of hydrau/ic and irrigation construction, together with the insufficient production of well-graded gravel-rabble material, has led to a search for artificial materials for filters: fabrics and nets forwater lowering and piezometric wells [1, 2], feIts made from mineral basaItic or glass fibers for hydraulic drains [3,4,5,8], etc. Such filters permit replacing several transition layers of sand-gravel filters by one layer of glass net or fiber. However, filters made from fibrous materials have found practical application only in horizontal pipe drains of irrigation and drainage systems and in piezometric and some other types of wells.In the period 1966-1969, the Ukrainian Branch of the 8. Ya. Zhuk Gidroproekt Institute and the Institute of Fluid Mechanics of the Academy of Sciences of the Ukrainian SSR conducted several investigations and design projects relating to the use of felts made from mineral fibers as inverted filters under pavements on upstream slopes and in the pipe drains of downstream slopes of earth dams. The basis for ~hese investigations and design work was the experience with the use of filters made from mineral-fibrous materials in hydraulic drains, as acquired by the Institute of Fluid Mechanicas of the Academy of Sciences of the Ukrainian SSR [7]. All the design work relating to different constructional elements of drainage zones was carried out in accordance with the Tentative Instructions [7].An inverted filter made from glass fiber and placed under cast-in-place reinforced-concrete pavement slabs on the upstream slopes of an earth dam was first contemplated by the Ukrgidroproekt in the design of the structures for the Mayachkovsk reservoir, on the Mayachk River in the Donets Region. This reservoir, which has a useful capacity of 7.8 million m a and forms a part of the structures intended for regulating the flow of the Kazennyi Torets River, provides protection against flooding of the Kramatorsk River and is at the same time a standby reservoir for the Northern Done ts-Donbass Canal.

Under conditions of daily fluctuations of the water levels in water bodies unsteady seepage is observed in the body of dams. With a rise of the level the inflow into soils of the structure from the upstream slope and outflow of seeping water from them into the foundation and drainage increase, r reaching maximum values at the normal pool level (NPL). With a drop of the water level the inflow and outflow of seeping water decrease, in which case, as a consequence of the low water yield of the soils and insignificant seepage velocity in them, the seeping water remains in the body of the earth structures in the form of a seepage mou~J, the surface level of which at the upstream slope is slightly below the NPL.The outflow of water from the mound Occurs along flow lines into the soils of the foundation and drainage of the lower pool (the water levels in which are considerably lower than the dead storage level (DSL) and without effluent seepage on the upstream slopes, as is seen from the flow nets of seepage through the body and foundation of a dam of homogeneous cohesive soils ( Fig. 1) and dam with a facing (Fig. 2). In a dam with a cutoff curtain the outflow of water from the sepage mound occurs only into the foundation soils with unloading in the bottom of the water body and also without effluent seepage on the upstream slope (~ig. 3).In all investigated cases, as a consequence of the absence of effluent seepage on the upstream slope at a water level in the water bodies drawn down to the DSL the protective coverings of the slopes do not experience an uplift pressure. This is important when protecting the upstream slopes by a filterless, solid reinforced-concrete covering.This type of covering, as is seen from the experience of operating a section of a filterless, solid reinforced-concrete covering of the upstream slope of the dike of the upper reservoir at the Kiev pumped-storage station [I, 2], reliably protects upstream slopes of dikes with daily fluctuation of the water level (Fig. 4). ..... ~zs 225,0 21~ (d -e Z20,O , I, --.~, .~s,.~21v~~j yl '~m~,~--.

No abstract