Selection of the revetment on the upstream slope of the upper reservoir at the Zagorsk pumped-storage station and its condition after seven years' service

Abstract

It is known that pumped-storage stations (PSSs) are the most mobile sources with respect to increasing and shedding the load within the daily load curve of a power system.Fluctuations of the water levels in the upper and lower reservoirs can reach more than 10 m in 24 h. In this connection the requirements imposed on the type of revetment of the upstream slopes of PSSs are high. A concrete or asphaltic concrete revetment on an underlying filter layer with discharge of the seepage water either under the water level or onto the downstream slope is usually used.The dam of the first phase of the upper reservoir of the Zagorsk PSS with a total length of about 5 km is made of morainal and blanket loams with horizontal drainage of a sand-gravel mixture on the foundation and inclined drainage at the foot of the downstream slope.For economic reasons and owing to the absence near the construction site of a sufficient number of quarries of the sand-gravel mixture with the required size distribution for the sand filter, a variant of revetment of the upstream slope in the form of a monolithic reinforced-concrete covering 20-cm thick without an underlying filter layer (filterless revetment) was used. To prevent rising of the revetment slabs from the action of the uplift pressure owing to their small thickness, monolithic reLqforced-concrete anchor teeth with a depth of 80-100 cm connected by reinforcing bars to the revetment slabs are provided for (Fig. 1). For sealing working and expansion joints, a preservative-treated board 25-m-thick and a 100 x 50 x 5-cm under-joint reinforced concrete plate covered with two layers of fiberglass fabric on bitumen were used (Figs. 2 and 3). It was assumed that such a revetment would be sealed, and the entire uplift pressure diagram would be divided into small diagrams in proportion to the distances between the anchor teeth.The ground for the tooth was excavated by an excavator with a 400-mm-wide reconstructed bucket. The tooth was concreted to the elevation of the bottom of the slab. After this the reinforcement of adjacent sections was joined and the recess left was concreted.Expansion joints were made every 40 m along the length of the slope. The size of the section was about 6 • 10 m. Revetting the slopes began in 1984. Several methods of placing the monolithic concrete and compositions were tested when concreting the revetment slabs.1. Placement of stiff f'me-grained (~-_nd) concrete with a slump of 0 cm with crane delivery of the concrete mix; manual smoothing; compaction by a plate vibrator designed by the All-Russian Institute for Planning and Organizing Power Construction (Org6nergostroi) equipped with two IV-24 vibrators moved by a crane through a winch. It was not possible to reach the calculated travel speed of the plate of 1 m/min necessary for compacting the concrete mix. The minimum travel speed of the plate reached was 3-5 m/rain. With this technology the surface of the concrete was smooth, but on drilling cores it was found that only the upper layer to a depth of 1-2 cm was...