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During the design and construction of the Nurek hydroelectric station, several advanced solutions regarding arrangement and design of the underground structures, which operate under high internal and external water pressures and flow velocities, were adopted. STRUCTURES UNDER HIGH INTERNAL PRESSURESFalling into the category of underground pressure structures at the Nurek hydroelectric station are three supply tunnels, each with trifurcations, nine penstocks, an intermediate supply tunnel with a trifurcation, and the upstream segments of the spillway tunnels from the intake portals to the regulating gates ( Figs. 1 and 2). Smoothing Out Lining with Antiseepage Rock GroutingThe 10-m-diam. supply tunnels pass through sandstones and aleurolites (siltstones) characterized by a strength coefficient of 5-10 according to M. M. Protod'yakonov.Each tunnel is designed to discharge 450 m3/sec, the internal static head ranges up to 85 m. Taking into account that the overlying thickness of surrounding rock is able to absorb the water pressure in the tunnels, they are provided with a non-load-bearing smoothing-out lining 500m m thick, using Mark-300 concrete, and reinforced with construction-type reinforcement (four rods of A-Ill steel per linear meter of tunnel). The internal water pressure is transmitted to the rock and to limit water loss from the tunnel, antiseepage grouting is carried to a depth of 5 m into the rock. The tunnels were temporarily strengthened by reinforced-concrete anchors and shotcrete 50 mm thick.In the intermediate supply tunnel to the hydroelectric station (D = 6.5 m, H = 130 m) a smoothing-out lining 400mm thick is also applied, using concrete of the same standard, reinforced with four rods of 20-and 28-mm diam. per linear meter of the tunnel. Antiseepage grouting of the surrounding rock was carried to a depth of 2-5 m. The tunnel has been operating continuously since 1972. Provision against Groundwater Pressure in Designing Pressure TunnelsExamples are known from practice where provision was made against groundwater pressure in designing pressure tunnels [i]. Proposals have been made which suggest that when there are low-permeabillty (e.g., grouted) rocks around the concrete lining of a pressure tunnel, one can, in designing the linings for internal pressure, take into account the pressure on the outer surface of the lining due to water seeping out of the tunnel [2].Taking the above into account, the antiseepage grouting in supply tunnels --as well as linings of the upstream pressure segments of diversion tunnels (from the intake structures to the gate chambers) --at the Nurek hydroelectric station were designed, taking into account also the groundwater pressure.In designing the antiseepage grouting system, the internal water pressure in the tunnels were taken to be 50% of the piezometric head, and the trough-shaped linings of diversion tunnels, which were provided with borehole drainage, were not designed for an internal pressure.This situation made it possible to adopt a smaller depth of antiseepage...
During the design and construction of the Nurek hydroelectric station, several advanced solutions regarding arrangement and design of the underground structures, which operate under high internal and external water pressures and flow velocities, were adopted. STRUCTURES UNDER HIGH INTERNAL PRESSURESFalling into the category of underground pressure structures at the Nurek hydroelectric station are three supply tunnels, each with trifurcations, nine penstocks, an intermediate supply tunnel with a trifurcation, and the upstream segments of the spillway tunnels from the intake portals to the regulating gates ( Figs. 1 and 2). Smoothing Out Lining with Antiseepage Rock GroutingThe 10-m-diam. supply tunnels pass through sandstones and aleurolites (siltstones) characterized by a strength coefficient of 5-10 according to M. M. Protod'yakonov.Each tunnel is designed to discharge 450 m3/sec, the internal static head ranges up to 85 m. Taking into account that the overlying thickness of surrounding rock is able to absorb the water pressure in the tunnels, they are provided with a non-load-bearing smoothing-out lining 500m m thick, using Mark-300 concrete, and reinforced with construction-type reinforcement (four rods of A-Ill steel per linear meter of tunnel). The internal water pressure is transmitted to the rock and to limit water loss from the tunnel, antiseepage grouting is carried to a depth of 5 m into the rock. The tunnels were temporarily strengthened by reinforced-concrete anchors and shotcrete 50 mm thick.In the intermediate supply tunnel to the hydroelectric station (D = 6.5 m, H = 130 m) a smoothing-out lining 400mm thick is also applied, using concrete of the same standard, reinforced with four rods of 20-and 28-mm diam. per linear meter of the tunnel. Antiseepage grouting of the surrounding rock was carried to a depth of 2-5 m. The tunnel has been operating continuously since 1972. Provision against Groundwater Pressure in Designing Pressure TunnelsExamples are known from practice where provision was made against groundwater pressure in designing pressure tunnels [i]. Proposals have been made which suggest that when there are low-permeabillty (e.g., grouted) rocks around the concrete lining of a pressure tunnel, one can, in designing the linings for internal pressure, take into account the pressure on the outer surface of the lining due to water seeping out of the tunnel [2].Taking the above into account, the antiseepage grouting in supply tunnels --as well as linings of the upstream pressure segments of diversion tunnels (from the intake structures to the gate chambers) --at the Nurek hydroelectric station were designed, taking into account also the groundwater pressure.In designing the antiseepage grouting system, the internal water pressure in the tunnels were taken to be 50% of the piezometric head, and the trough-shaped linings of diversion tunnels, which were provided with borehole drainage, were not designed for an internal pressure.This situation made it possible to adopt a smaller depth of antiseepage...
The development of water-power construction in the USSR can be divided into several periods: the first --realization of the plan proposed by the State Commission for the Electrification of Russia; the second --the prewar period, which saw the exploitation of the Dnepr and Volga rivers and the Caucasian and Kola peninsulas, and the initial explltatlon of the rivers of Central Asia; the third --the post-war period, which saw the rapid completion of the exploitation of the Volga and Dnepr and Trans-Caucasla and the start of construction on hydroelectric plants in Siberia; the fourth --the systematic exploitation of the Angara and Enisei and the start of construction on the first hlgh-head hydraulic facilities; the modern period --the construction of hlgh-head hydro projects in the alpine and foothill regions of Siberia, the Far East, Central Asia, Northern Caucasia, and Trans-Caucasia.In the initial period, water power was based on fundamental studies of prominent Russian scientists of the prerevolutlonary period, and on foreign experience and techniques in practical matters. Later, the development of water-power construction in the USSR took a course that differred markedly from foreign experience. This was determined by the need for the rapid solution of the most complex problems on which the developed capitalist countries had a considerable head start and by the natural construction conditions, which differred from those in the European countries. All this served to create the Soviet school of water-power construction, which had captured substantial international authority. The services rendered by the journal G~otekhn~cheskoe Stz, oitel'stvo, which since its establishment, has taken a leading position in shedin8 light on problems associated with water-power construction, and, particularly, in problems involving the organization and production of work, have been important to the creation of the school. Since the first years, the Journal has been an aid to Soviet, and, recently, to foreign specialists.The journal has exposed and promulgated basic ideas concerning the improvement of such trends in water-power construction as: the overall organization of construction; the closure of river channels and the organization of the concrete, rock-crushing, gravel-screenlng and other establishments required for the building of hydraulic structures; the mechanization of concrete and earthwork, and mechanism for the production of these operations; the compositions of concrete mixes; study of the thermal-stressed state of dams; tunneling, dewaterlng, and consolidation operations; and, the assembly of metallic hydraulic designs and hydraulic equipment and other trends in the organization and production of work.
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