and V. I. BelovaMakeup and Organization of the Control of the State of the Concrete Structures. The makeup and extent of the observations on the structures during their operation were partially determined in the design stage and were finally established during construction and the initial Period of project operation. The observations include control of the seepage regimen, settlements, displacements, stress state of the reinforced-concrete elements, and temperature regimen of the water and the reinforced-concrete elements. During the design, construction, and initial operation stages the observations were conducted by personnel from the Gidroproekt Institute, who installed the controlmeasuring instrumentation (some of the piezometers were installed by the constructors).At the hydraulic shop is a group of nine men in charge of control of the state of the hydraulic structures. This group, headed by a senior engineer, is divided into two specialized groups: 1) one in charge of surveying observations consisting of an engineer, a foreman, and three workers (it carries out also surveying observations on the state of the hydraulic stzuctures at the Kegmnsk hydroelectric plant); 2) one in charge of piezome~ic observations and of observations on the stress state of the structures, made up of an engineer and three workers. The personnel at the hydraulic shop gradually acquired experience with all the observations, thanks to the technical assistance provided by the Gidroproekt Institute. The seepage observations have been conducted since 1967, the observations on the stress state of the reinforced-concrete elements since 1968, and the observations on the settlements and displacements of the structures since 1970. Of special importance in the system of structural control is the period of inundation of the pit and filling of the reservoir. To enhance the reliability of the results of the observations carried out by the shop personnel, it is necessary to complete a set of operation observations during about 1.5 years before the pit is inundated and the head on the structures is increased, which will enable the personnel to acquire sufficient knowledge about the instruments and the observation methods and to become prepared for the work.Makeup of the Control-Measuring Systems. The observations on the seepage regime of the structures are carried out by means of embedded and contact piezometers as well as devices for measuring the flows. Observations are carried out also on the penetration of sand into the deep drainage self-venting wells. A total of 317 piezometers was instaUed in the plant structures,* as follows: at characteristic points along the underground contour of the pow-I! Fig. 1. Flew-measuring tank in overall drainage wells. 1) Metal tank; 2) opening establishing the end of the measurement; 3) opening establishing the initiation of measurement; 4) valve for closing the outlet tube; 5) measuring volume; 6) drainage well. erhouse, 67 piezometers, of which 19 were embedded and 48 were contact types; in the water-holding...
GENERAL INFORMATION ON STRUCTURES AND MONITORING EQUIPMENTThe Riga hydroelectric station --the lower reach of the sequence of hydrostations on the Daugava River with a capacity of 384 MW--is intended for covering the peak part of the load curve of the Unified Power System of the Northwest of the USSR. In view of the peakload operating regime the daily range of variation of the water level in the lower pool reaches 4m at a maximum head of the hydrostation of 18 m.The length of the station structures ( Fig. i) is 15.4 km; earth dams and embankments compose the greater part of the upstream face. The embankments are located along both banks of the river.
The Plyavinyas hydroelectric station is the third in the sequence of hydroelectric stations on the Daugava River (Fig. 1). Its capacity is 825,000 kW developed by I0 units using mixed-flow turbines under a head of 40 m. Numerous national economic problems were solved by constructing the hydrodevelopment [1].With respect to complexity and unusualness of the hydrogeologic conditions [2] the construction of the Plyavinyas station (Fig. 2) has no analogs either in Soviet or foreign hydropower construction practice. The presence of high-pressure water-beating horizons in rocks of the Amata-Gauya suite (Upper Devonian) and talus and Plyavinyas suite (Upper Devonian! related with it and the character and uniqueness of the moraine soils in the foundation, particularly the presence of moraine sandy loams expanding under a certain head of artesian waters, created difficulties and the need to conduct additional work during construction and required the creation of a complex drainage system for relieving the indicated artesian horizons for normal operation of the hydrodevelopment.
Effectiveness of monitoring the condition of structures from the viewpoint of the operating personnel --this means sufficient knowledge about the work of the structures to ensure their safe and reliable condition obtained with minimum expenditures of labor and means. The hydraulic structures of the cascade of Daugava hydroelectric stations (Plyavlnyas, Kegum, and Riga) differ with respect to the head being absorbed, length of the upstream face, and geologic and hydrologic conditions [1-3]. The structures of the Plyavinyas hydrostation are situated under the most complex hydrogeologic conditions, and the structures of the Kegum hydrostations under the most favorable.
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