Hydrotechnical construction in recent years has been characterized by complex natural conditions of operation of the structures and an increase of the height of dams and storage capacities of reservoirs.These circumstances, just as the increase in the number of hydrostations and increasing wear of earlier constructed structures, are causing an increase of the requirements imposed on their safety.Problems of a theoretical evaluation of the quantitative indices of reliability of hydraulic structures and especially their life, as is known, still do not have a satisfactory solution. Attempts to use the theory of reliability of machines, mechanisms, and other massproduced devices for determining the probability of failure of the structure run into considerable difficulties related to the individual characteristics of each structure and its operating conditions. Therefore on-site observations are presently regarded as the main means of ensuring safe operation of structures.We will examine below one of the aspects of this problem --the direct use of the readings of monitoring and measuring equipment (MME) for timely detection and assessment of dangerous phenomena and processes during operation of structures and their foundations related to possible redistribution of loads, changes in the characteristics of the strength of materials, failure of individual elements, etc. Such phenomena and processes can lead to an emergency situation, in which case the MME will record the immediate progressive changes in the operating indices of the structure [i].In conformity with the construction standards and operating regulations [2, 3,4], the conduction of on-site observations should be organized on all hydraulic structures for evaluation of the state of the "structure--foundation" system, timely detection of defects, prevention of accidents, and improvement of the operating conditions.In this case the observations for structures of the I, II, and III classes should be carried out by means of the MME, and visual observations are sufficient for structures of class IV. Monitoring observations of deformations, settlements, opening of joints, seepage force and discharges, stresses, etc., should be conducted on the structures.Prompt evaluation of the state of the structure from the results of these measurements encounters considerable difficulties, especially on operating structures, owing to the limited number or even absence of qualified hydraulic engineers among the operating personnel.In connection with this it is considered necessary to determine for each structure the maximum permissible or "critical" values of the physical indices so that on comparing them with the readings of the MME the state of the structure can be promptly evaluated.This requirement is given in a number of departmental directives and in individual new standards (e.g., [5]), but its fulfillment runs into considerable difficulties owing to the absence in previously published Construction Specifications and Regulations (SNIP) of instructions concerning the method ...

To increase the overhaul time of the turbine bearings at the Kremenchug hydrostation the following measures were taken:i. The rotors of the units were balanced by placing weights of 450-800 kg on the rotor rim. 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. The ellipticity of the turbine bearings was determined and eliminated. Ellipticity was determined by measuring the gaps between the rubberized bushings and turbine shaft with the thrust bearing raised. The gaps were measured by a special gauge witha vernier. Three measurements at the trailing and leading edges and in the center (a, b, c) were taken opposite each segment.The measurement results are given in Table i. A further determination of ellipticity was carried out by the graphic method with the use of the data of column 6 of Table i. With the use of an arbitrary circle at a scale of 10:1 (or any other scale) the values of the deviations from the circle are plotted with the use of the data in column 6 of Table i. A circle is inscribed in the figure obtained and the final values of the deviation from a circle (ellipticity) of individual segments of the bearings in millimeters are determined.Individual shims are installed under segments having deviations from a circle of more than 0.3 mm to eliminate ellipticity. In addition to this, shims of the same thickness are installed under all segments (including under the segments with individual shims) in accordance with the data of "rocking" or play of the shaft before repair. Turbine bearings with elimination of ellipticity last the overhaul period with allowable values of play of the shaft.The accomplishment of the indicatedmeasures considerably increased the operational reliability of the bearings of the units of the Kremenchug hydrostation.The concrete dam of the Toktogul hydroelectric station, constructed in a narrow canyon of the Naryn River, is a massive structure consisting of a central and six side sections (three on each bank). The total height of the\dam is 215 m with a base width along the flow of 173 m.Thick-layered, quite strong marmorized limestones with widespread wall and bottom release joints are the foundation of the dam. 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]. Systematic filling of the reservoir began in August 1977. By mid-1980 the upper pool level reached the maxi...

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