The problem of the design and construction of penstocks for hydroelectric stations is practically solved. Thus, steel penstocks are usedfor high-head diversion hydroelectric stations in open stretches (Gizel'don, Baksan, Azma, Khrami, Gyumush, Sukhumi, and Krasnaya Polyna hydroelectric stations). Both steel penstocks (Svistukha, Egorlyk, Perepadnaya-l, Chir-Yurt, Mingechaur, Perepadnaya, Central Farkhad hydroelectric stations) and reinforcedconcrete penstocks (Zemo-Avchal'sk, Dnepr-2, Onda hydroelectric stations) are used for lowand medium-head reservoir hydroelectric stations. In our country there is experience [I] in constructing conduits from in situ concrete with prestressed bars with a diameter of 2.5 and 2.8 m for a head of 55m onthe 15-km-long Northern Donets--Donbas canal, from precast prestressed reinforced-concrete elements with a diameter of 2.8 m for a head of 40 m (0.7 ~an) and from precast elements without prestressing (4.5 km) on the Dnepr--Krivoi Rog canal. Finally, precast prestressed pipes with a diameter of 4 m (3.7 km) are used at the Kuban--Kalaus hydroelectric station.Two designs are used for high-headreservoir hydroelectric stations: eitherthe Conduit with a metal lining is located directly in the body of massive dam (Bratsk, Ust'-llm, Bukhtarma, Toktogul, Boguchany, Mamakan hydroelectic estations) or the concrete-encased conduits extend from the body of the dam to the downstream face (Krasnoyarsk, Sayano-Shushenskoe, Chirkey, Kurpsai hydroelectric stations).When designing the penstocks of pumped-storage stations (PSSs) it is necessary to solve a wide range of new engineering problems. They include first of all the selection of the route of the penstocks with consideration of the engineering-geologic conditions and general layout of the station. As a rule, for the PSSs examined in this article the route of the penstocksruns along a slope composed~soil rather than rock. Traces of landslide phenomena are often found already during surveys. Therefore, when designing penstocks it is necessary to assess the stability of the slope and to develop engineering measures to increase it. Such measures include primarily flattening of the slope, control of the levels and drainage of groundwaters, and grading and stabilizing the slope with construction of a surface water drainage system. The general and decisive conditions for selecting the design of a penstock for the investigated type of PSS are: location of the open route of the penstocks on slopes composed of soils; averageslope of the route of the penstocks 1:6-1:10; the relatively small design head (90-120 m) for PSSs, which for units with an individual capacity of about 20OMWpredetermines the turbine discharge of up to 250 mS/sec and penstock diameter from 6.5 to 8 m.Here it is timely to examine the problem of the reliability of the designs of metal penstocks, on the one hand, and of reinforced-concrete and concrete-encased penstocks, on the other.Despite the fact that among construction materials metal is distinguished by a high homogeneity and ...

Layout and Design of Installations. The Toktogul hydroelectric station comprises ( Fig. 1)a station building adjacent to the dam, a solid concrete dam, the underground complex of reinforcement, antiseepage and drainage measures, and installations for passing the construction discharges.The site was selected basically from the standpoint of locating the main installations in a single structuraltectonic block, which greatly reduces the probability of permanent deformations from heavy earth tremors. The station building is attached to the downstream face of the dam. The water intake is located in the dam. The design flood and emergency discharge are passed through two spans of the surface spillway, two submerged openings, and three turbines.Power is transmitted at 500 kV from the station to the Naryn River by cables in a tunnel and then by overhead Kne across the water divide to the switchyard in the Kara-Su River valley.Equipment is transported to the station building and its control sector along the left bank tunnels. There is an operational runnel 2.8 km long from the Kara-Kul settlement to the crest of the dam.Equipment for controlling the gates on the submerged spillways is delivered along the rigl= bank tunnel which emerges at the 897-m level. This tunnel is used in the construction stage as the main transport route for conveying concrete and other building materials when erecting the dam.

The construction in our country of pumped-storage stations with 7.5-m-diameter opentype reinforced-concrete conduits operating at a water pressure up to 200 m required the development of a special design of an expansion joint. This work is performed by the research department of the All-Union Planning, Surveying, and Scientific-Research Institute (Gidroproekt) together with the institute itself. As a result of design and experimental investigations, several designs were substantiated which can find use in hvdrotechnica] construction p=actice. An expansion joint with the use of a waterproof joint of glassfabric stretch material was examined in [I]. However, this solution has a number of shortcomings: it is necessary to develop a special technology on manufacturing the indicated joint, its dimensions do not permit transportation by vehicle, the use of special compositions on an epoxy resin base is required for its manufacture and assembly, and there is the danger of mechanical ~damages during assembly and operation.Therefore the task of developing and substantiating a simpler design was undertaken: not requiring parts manufactured with the use of special machine tools; permitting delivery of the parts to the construction site by vehicle; not needing a preliminary check assembly; not requiring the creation of special sealing shapes; making it possible to assemble the butt joint under conditions of the construction site; having the required reliability and maintainability.With consideration of the aforesaid, a design was proposed in which the gap between sections was covered with flat steel and rubber sheets.The butt joint (Fig. i) represents a steel cover plate 2 covered by a rubber strip 3. The steel over plate is made closed along the perimeter and one edge is welded to the lower section of the fragment of the conduit i. The second edge of the steel cover plate is left free and during work of the joint slides along the upper section of the fragment of the conduit. Therefore, it is necessary to machine (to round and trim) this edge and to make in it cuts to a certain depth every 150 mm around the circumference to increase the deformability of the cover plate. A tight fit of the edge of the cover plate against the conduit under pressure is achieved by this. The rubber strip is made closed along the perimeter and is fastened to the fragment of the conduit by bolts 4 and metal elements 5 and 6. Cover plates 5 are made of plate steel and the sole plate of sheet steel.Cover plates 5 are made split and are installed with a gap. To prevent damage of the rubber by these cover plates when tightening the bolts, a steel strip 6 (sole plate) is placed under them.A special testing complex consisting of a test stand, fragment of the conduit, and hydraulic jack, was developed and manufactured for an experimental check of the performance of the proposed design of the expansion joint (Fig. 2). The stand was made up of a lower

In conformance with current design norms [1], the shape of the modern concrete gravity dam is selected on the basis of a condition whichis prohibitedinthedam and in its contact with the foundation, which is tension, and in addition, for a basic loading combination in all sections, the minimum principle compressive stresses on theupstream face should be not less than 1/4 the value of the hydrostatic pressure. For any particular loading combination the exclusion of tensile stresses is mandatory, and the requirement that compressive stresses be maintained at not less than 1/4 the value of the hydrostatic pressure applies only to the contact between the dam and foundation.The reason that these conditions must be fulfilled is the need to prevent crack development and to limit the counter pressure of the water in the concrete mass. Domestic and foreign experience gained with dam construction indicates, however, that crack development is practically eliminated on the upstream face, and failure occurs along the contact with the foundation. Temperature effects and the development of tensile-stress regions in the foundation below the contact in the direction of the upstream face of the dam are the basic reasons for crack development[2, 3]. Generally, it is virtually impossible to satisfy normal requirements for dams situated in regions susceptible to high seismic activity [4].The absence of catastrophic consequences resulting from crack formation can be explained by the comparatively shallow depth of crack development and the effective performance of the drainage, which is a mandatory structural element for the dam and subsurface contour. Fulfillment of the above-cited standard requirements results in the fact that the compressive strength of the concrete is not fully developed (usually by 10-15%). As a result, the volume of a gravity dam, as a rule, significantly exceeds the volume of a buttress dam, in which the properties of the material are more fully utilized. As a result of this, the gravity dam is frequently not considered, although it always attracts attention due to the simplicity of its design, which makes it possible to employ the most inexpensive means of placing concrete; to its size, which is smaller than other types of dams; to the dependence onthe quality of the foundation; and to the possibility of obtaining a compact grouping of basic structures within the hydraulic facility. These advantages offered by gravity dams compel us to search for new means of improving their design in order to reduce their cost. As one approach, we can propose the following:1. Select the shape of the dam from the compressive strength of the concrete in the zone of its downstream face, the strength of the foundation beneath its base, and the ability of the dam as a whole, and of its individual parts, to resist plane shear and overturning; 2. Assuming the formation and exposure of cracks, do not restrict the magnitude of the tensile stresses in the upstream face, including the contact zone;3. In order to exclude the counter pressu...

No. 61 (1978The intakes of pumped-storage stations (PSSs) equipped with reversible units operate under complex hydraulic conditions with convergent (turbine) and divergent (pump) flow regimes in the conduit. The latter are characterized by nonuniformity of the velocity and pressure fields, increase of energy losses in the outlet with large angles of divergence, and worsening of the operating conditions of the mechanical equipment. Cases of failure of the conduit lining and bars of the trash racks are known. The hydraulic conditions in the offtake can considerably worsen in the case of a nonuniform vertical velocity distribution at its inlet (in the presence of an elbow in the transition between the intake and conduit). That is, when designing an intake-offtake a certain conflict occurs between the requirement of providing minimum losses in the compressed convergent inlet portal of the turbine intake with preservation of the standard velocities Vr ~ 1.5 m/sec at the site of the rack (the degree of constriction of the section reaches m = ~in/mcon = 5-7) and the striving to reduce losses in this same section in a pump operating regime by reducing the expansion angles of the diverging duct (the degree of expansion should not exceed m ~ 3). This conflict can be resolved either by increasing the dimensions (length) of the intake or by increasing the permissible velocities of the trash rack (decreasing the inlet area). Obviously, the problem is solved on the basis of a technical and economic comparison of variants with the use of the initial data on the energy characteristics of the intake.For the Zagorsk and Kaisiadorys PSSs equipped with large reversible units with a capacity of 200/217 MW and discharges of 226/189 mS/sec a model investigation was carried out for numerous layouts of the intakes with various dimensions (L i = 5-1ODcon, B = l-2Dcon) , angles of convergence of the inlet section ~ = 40-6 ~ and shapes and configurations of the boundaries and transition sections. Minimization of the enery loss function in turbine and pump regimes was the basis for selecting the optimal variant.The investigations showed that intake schemes with angles of total divergence 8-12 ~ correspond to minimum total losses, which radically differs from the geometry of the intakes of hydroelectric stations. Accordingly, for the Zagorsk PSS a variant of a compressed intake (Fig. i) with the following dimensions was designed: total length of intake L i = 60.15 m = 8.17Dcon; angle of total convergence (divergence) ~ = 8.1~ length of inlet section 11 = 22.2 m = 2.95Dcon; angle of convergence (divergence) of the inlet section a~ = 17.5~ angle of convergence in plan B~ = 7.2~ configuration of the upper face of the portal radially R = 4Dcon; length of the straight section Z2 = 20.15 m = 2.87Dcon; width Of the straight section b= = 7.5 m = Dcon; length of the transition from square to round Is = 15.5 m = 2.0Dcon; angle of convergence (divergence) of the transition ~3 = 4 ~ A special feature of the design of the intake is an overhanging portal ...