Experience in concreting the Toktogul'sk HES dam

Abstract

The Toktogul'sk Hydrocenter* is located on the Naryn River in a narrow canyon with steep (60-78*) slopes rising to 1200-1300 m above the dam's crest. The canyon's geological structure consists of limestones with developed lateral release cracks (to a depth of 50 m) and a system of intersecting tector~ic cracks. The high seismicity of the construction region (force 9-10) and the presence of potentially unstable blocks on the slopes required the implementation of a complex of undertakings [1] before the main work of excavating the foundation pit and of pouring the concrete into the structure could proceed. The sharply continental climate of the region with a long-term temperature range of 84"C and a mean annual temperature of + 8.4~ is, unlike that of Siberia and the North, characterized by sharp fluctuations in mean daily temperatures in the fall-winter-spring periods and in diurnal temperatures reaching 20-25"C [2].The concrete-gravity dam is 215 m high, 40 m long at the base and 300 m at the crest, and will contain 3,200,0O0 m 3 of concrete. During the erection of the hydrocenter, construction discharges are passed through a diversion tunnel with a system of check dams. Because of the difficult topographic and mining-geologic conditions, the auxiliary enterprises are located on individual construction platforms along both banks of the Naryn and on the floodplain terraces of its tributaries, the Karasu, Karskol, and Keinda.The concrete works, located on the Naryn's left bank 5.5 km from the hydrocenter site, include: a 220-m3/h concrete plant with eight 2400-hp concrete mixers; a cement warehouse; an installation for storing ice; an air compressor; a refrigeration station for water cooling and ice making; installations for cooling coarse aggregates; asteam ejector installation for cooling or heating sand; a boiler room, etc. The gravel-grading plant is located on the same bank 11.5 km from the site. The raw material from a gravel pit is transported 2-5 km to the gravel-grading plant, whence the gravel and sand are carried in dump trucks to the bunkers of the concrete works, 6 km away. The concrete mix is transported 5.5 km to the dam site in KrAZ-256 dump trucks on the right-bank road. In the immediate vicinity of the dam site the transportation system changes as the dam rises. Difficult natural geologic, topographic, and climatic conditions necessitated the development of new methods of concreting, which along with rapid concrete placement ensured a monolithic and crack-proof dam. In considering numerous methods of operation, cable and turret cranes were rejected because of the impossibility of approaching the dam near the crest level and of placing the required number of concrete-pouring machines at the level of the s~ucture's base or near it. Building concretecarrying trestles under the natural conditions of a narrow canyon also proved irrational. The principal features of the concreting technology developed and mastered in the dam's construction is the complex mechanization of the delivery, unloading, spreadi...

Characteristics of horizontal construction joints at the Toktogul'sk hydroelectric plant

“…This feature leads to full mechanization of the concreting operations, as well as a considerable reduction in the number of vertical joints. This in turn, improves the monolithic nature of the structures [1,2]. At the same time, the number of horizontal construction joints is significantly increased.…”

Condition of the concrete dam of the Toktogul hydroelectric station according to on-site observation data

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To increase the overhaul time of the turbine bearings at the Kremenchug hydrostation the following measures were taken:

i. A front grout curtain and drainage in the foundation and canyon walls are the cutoff measures.The characteristic design features of the dam are the absence of cuts into the canyon walls, the use of an additional surcharge by water, and the presence of deformation joints between sections in the shape of a fan, which made it possible to direct the main load to the foundation of the structure and to provide independent deformation of each section [i, 2].The dam was constructed by the layer-by-layer method with sectioning into concreting blocks measuring 60 x 32 m in plan and 0.5-1 m high [3]. Balancing was carried out by the method and under the supervision of workers of the I. I. Polzynov Central Boiler and Turbine Research and Development Institute with consideration ofmechanical, electrical, and hydraulic imbalance.

2.

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“…The dam was constructed by the layer-by-layer method with sectioning into concreting blocks measuring 60 x 32 m in plan and 0.5-1 m high [3]. Systematic filling of the reservoir began in August 1977.…”

Increase of labor productivity in multipurpose hydraulic construction

“…The correct organization of production" presupposes improvement in the plan of construction operations, 9 The maximum economic effect in multipurpose hydraulic construction can be obtained by radical improvement of construction operations. As a favorable example we can cite the use of the so-called Toktogul'sk method of pouring concrete, which enabled the Naryin Hydroelectric Station Construction Trust to increase labor productivity in 1971 by 128% while keeping the average wages at the 1970 level [9].…”