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1.
1.  A study of the strength and deformation properties of asphaltic concrete is necessary for analyzing the stress-strain state of dams with asphaltic concrete diaphragms. The properties of asphaltic concrete substantially depend not only on composition but also on temperature. The results obtained make possible an evaluation of the main deformation and strength properties of asphaltic concrete, diaphragms, and facings of dams in relation to composition and temperature at early design stages.
2.  To obtain generalized indices of properties in relation to composition and temperature of asphaltic concrete, all experiments were conducted on the basis of the mathematical theory of design of experiments. Each experiment had threefold replication.
3.  The experiments showed that the angle of internal friction for 7% bitumen in excess of 100% of the mineral part is practically independent of temperature. The strength of the material increases due to cohesion, which with a drop of temperature from 200 to 10 increases about fivefold.
4.  Investigation of the deformation properties of asphaltic concrete showed that the modulus of volume changeE 0 for=0.1 MPa varies by 4–7 times depending on the temperature.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 5, pp. 26–30, May, 1989.  相似文献   

2.
1.  The prefabricated cutoff wall as one of the economically justified designs can be regarded as the main watertight element of an earth dam.
2.  The cutoff wall can be made from precast asphaltic concrete and concrete blocks and combined — from both joined together on asphalt mastic. An analysis of the stress-strain state showed that each of these walls has a sufficient margin of deformability.
3.  The cutoff wall of precast concrete blocks, eliminating the use of asphalt for its construction and having a practically unlimited margin of deformability, can be of interest to designers and builders.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 11–14, November, 1993.  相似文献   

3.
1.  Oscillations due to low-frequency sources of excitation beneath the impeller in the draft tube develop in long pipelines of water-storage power plants.
2.  For the Zagorsk water-storage power plant with a long (790 m) and flexible pipeline, the natural frequency of the first type of the system's oscillation is many times lower than the predominant frequency of the lowest-frequency component of the spectrum of pressure fluctuations beneath the impeller (0.24–0.25)fre. For a shorter and stiffer pipeline, the system would approach resonance.
3.  The dynamic properties of the system depend on the opening of the guide apparatus: for small openings, the natural frequency approaches f1=(C/4)L; with large openings, it approaches f2=(C/2)L.
4.  When the unit is operating in the stationary mode, the hydrodynamic loads on the pipe lining do not exceed 0.05 MPa; this corresponds to an additional stress of 0.07 MPa in the lining and vibrational displacements of 0.183 mm (when C=780 m/sec), i.e., not more than 0.06 of the radius of the pipeline; when C=965 m/sec, the vibrational displacements do not exceed 0.08 mm.
5.  The loads on the pipeline supports do not exceed 0.36 tons on any one pile.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 8, pp. 27–30, August, 1992.  相似文献   

4.
1.  The results of the first full-scale experiments with orthogonal wind turbine generator units showed their performance, the possibility of creating on their basis large units of a simple design intended mainly for use in power systems.
2.  The maximum wind power coefficient of the rotorC n somewhat exceeds the calculated values, reaching values of 0.50–0.56 at blade speeds equal to about three wind speeds.
3.  The aerodynamic drag coefficients of structural elements of type VL-2 rotors with guys can reach a=0.06–0.07, which substantially exceeds the profile drag of the operating blades. Elimination of the guys and a relative increase of the area of the working blades in type VL-2N rotors makes it possible to reduce the indicated drag coefficient to a=0.031–0.033.
4.  At wind speeds exceeding 0.5–0.6 the blade speed and power output of the unit cease to depend on the wind speed. This property of orthogonal units protects the generator from overloads, simplifies regulation, and increases the reliability of the plants.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 49–53, November, 1988.  相似文献   

5.
1.  To reduce the cost and construction time of hydro developments, it is necessary to introduce more widely continuous concreting technologies. Concreting of heavily reinforced and thin-walled structures and members is most effectively done with cast concrete mixes by means of modern concrete pumps.
2.  As a result of experimental investigations of pipeline delivery of mixes by BN-80-20 concrete pumps, the values of the specific resistances during pumping of various compositions of the mixes and the local resistances of quick-disconnecting pipe connections were determined; recommendations were developed for calculating the distance of pipeline transport of the mixes by the concrete pumps; the values of Kf, the volume filling of the transport cylinders of the concrete pump with the plasticized concrete mix, and Kd, the inertial component of the pressure during displacement of the mix, were refined.
3.  The two-year experience of using the means (conveyors, concrete pumps) of craneless technology of placing concrete for construction of the powerhouse of the Shul'binsk hydro development showed that even with the high price and underutilization of the potential possibilities of the equipment and mechanisms, a considerable savings was obtained due to shortening of the construction time and start-up of the first unit of the hydrostation ahead of schedule.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 10, pp. 38–43, October, 1990.  相似文献   

6.
1.  An intake structure with a closed flow having a vertical axis of rotation contributes to the development of a favorable kinematic structure in the channel, which makes it possible to minimize scouring beyond the structure.
2.  Excedence of the near-bottom average and maximum velocities above the average velocities in the channel comes about atl3.3hc downstream from the axis of the intake.
3.  The magnitude of the ratio of the maximum 1st-percentile and average 50th-percentile flow velocities (v1%/v50%), which characterizes the velocity pulsation, attains values for the undisturbed flow in the near-bottom region at a distancel4.1hc.
4.  Complete equalization of the plan diagram of velocities is noted at a distance (4.9–7.8)hc from the axis of the intake structure.
Translated from Gidrotechnicheskoe Stroitel'stvo, No. 4, pp. 17–19, April, 1991.  相似文献   

7.
1.  The character of the process of compacting a PAC mix on sand and on clay materials has substantial differences. On sand vibro-compaction is more effective with a high value of acceleration, 100 m/sec2; on clay materials the highest quality of compaction occurs with insignificant acceleration of vibro-compaction, 40 m/sec2.
2.  It was established that PAC mixes are compacted more effectively on sand having a modulus of deformation not lower than 40 MPa. If the modulus of deformation of the base is lower, it is recommended to strengthen and additionally compact it.
3.  On clay materials having a low modulus of deformation, the quality of compaction of the PAC mix is low, and therefore it is recommended to strengthen them.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 12, pp. 45–47, December, 1988.  相似文献   

8.
1.  Tests confirmed the reliability of the work of the reinforced concrete-encased steel design of the link of the penstocks of the Zagorsk pumped-storage station in the range of pressures up toP=1.4 MPa. The lining of the link and hoop reinforcement of the inside and outside rows take the tensile load in the elastic stage.
2.  The allowable opening of cracks for reinforced concrete-encased designs of a penstock with an inside sealing lining in the range of pressures up to 1.6 MPa with a width of the cracka c 0.2 mm does not exceed the standard requirements.
3.  The test of a particular link showed that with loading by an internal pressure the lining takes 30%, the reinforcement of the inside row 23%, and the reinforcement of the outside row 47% of the external load.
4.  The tests confirmed the complete correspondence of the work of the link to the design data and earlier investigations carried out in a range of pressures exceeding the operating pressure by 30%.
Deceased.  相似文献   

9.
1.  For short revetmentsl r/l j<1.5, the=" vertical=" component=" of=" the=" fluctuation=" instantaneous=" bottom=" velocity=" has=" a=" considerable=" effect=" on=" the=" depth=" of=" the=" scour=" pocket.=">
2.  The results of investigating the velocity structure of the flow obtained on erodible models with a length of the revetment less than 1.5l j and limited time of the experiment do not reflect the actual kinematics of the flow in the pocket in the case of completely stabilized scouring.
3.  For the velocity-squared region of resistance of the channel and revetment lengths less than 1.5l j, as well as for the transition region of resistance and revetment length less than 2l j, it is necessary to carry out artificial lowering of the bottom of the lower pool to obtain the kinematic characteristics of the flow corresponding to stabilized scouring.
4.  For a revetment length equal to or greater than 2l j, the results of investigating the kinematic structure of the flow obtained on the model can be transferred to the prototype without correction.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 12, pp. 42–45, December, 1991.  相似文献   

10.
1.  The installation of a conical transitional segment between a tower (shaft)-type water intake-outlet and penstock affects a significant reduction in head loss in the pump mode, but has virtually no effect on the magnitude of the latter in the pump mode.
2.  The existence of a conical transitional element in the pump mode appreciably lowers the discharge velocities of the flow and increases the effective height of the water-passing openings by 1.5–1.7 times when the height of the intake openings h0.5dp.
3.  The head losses in the intake-outlet decrease in the pump mode of operation with increasing degree of expansion of the transitional diffusor segment.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 21–23, November, 1992.  相似文献   

11.
1.  A considerable increase of the content of sand in comparison with ordinary concrete mixes is required for preparing workable fiber-reinforced concrete mixes. The optimal content of sand should be selected experimentally in relation to the particular properties of the aggregates and length, cross section, and content of fiber. Fiber can be regarded as a coarse aggregate of acicular form with a developed surface, for binding of which an increased quantity of the mortar component is necessary.
2.  When using fiber in the form of wire lengths without additional anchorage on the ends, its length can be taken equal to 60–65 diameters without a substantial decrease of the tensile strength of the fiber-reinforced concrete. A reduction of the length of the fiber to these limits considerably decreases clumping of the fiber during mixing.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 10, pp. 38–41, October, 1989.  相似文献   

12.
1.  An increase in the oil temperature in baths of bearings with EMP segments from 30–35 to 60°C leads to a decrease of friction losses by 20–30% due to a decrease of the oil viscosity in the oil film, and also produces an additional effect from a reduction of the consumption of water for cooling.
2.  A decrease of the operating reliability of the bearings with EMP segments does not occur when the oil temperature in the bath is increased to 60°C. Therefore there is no need to introduce restrictions in the operating regimes of the units.
3.  The existing systems of sealing the oil baths of the bearings do not prevent the escape of oil vapors from the oil baths at an oil temperature of 55–60°C. Therefore reconstruction of the seals is necessary before changing to an oil temperature increased to 60°C.
4.  On operating units of hydrostations it is expedient to increase the oil temperature in the baths of the bearings from 30–35° to 45–50°C by reducing the flow rate of the cooling water or disconnecting a part of the coolers, which leads to a decrease of friction losses by 12–15% and does not noticeably increase the escape of oil vapors from the bearing baths.
5.  On newly designed bearings with EMP segments it is expedient to specify a smaller number of oil coolers, and it is possible to do away with them entirely by increasing the cooling capacity of the walls of the oil baths, for example, by means of fins on them.
6.  To reduce losses in the bearings, the use of other, less viscous oils or other low-viscosity liquids is possible.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 20–24, November, 1990.  相似文献   

13.
1.  The hydraulic characteristics of cohesive mudflows in the case of a hydraulic jump, other conditions being equal, differ considerably from those for a pure water flow.
2.  The scheme of calculating a hydraulic jump of a cohesive mudflow requires taking into account, along with the hydrostatic pressure, also the pressure caused by cohesive forces and angle of internal friction of the mudflow mixture.
3.  The change in the ratio of the depth H2/H1 before and after the jump completely depends on the kinetics parameter of the mudflow, values of cohesion and angle of internal friction.
4.  Several subcritical depths, determined by the concentration of the mudflow mixture and physical and mechanical properties of the medium, correspond to the jump function of a cohesive mudflow.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 12, pp. 45–47, December, 1991.  相似文献   

14.
1.  Blocks in fill experience a maximum force effect under conditions of wave action close to resonance when tan 0(h/gT 2)–1/2=4.4–7, in which case the stability coefficient acquires a minimum value.
2.  Formula (19) recommended for calculating the characteristic size of a block D (or the mass of a block d=0.52 mD3) satisfactorily agrees with the laboratory and actual data and advantageously differs from the suggestions known from the literature.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 7, pp. 18–20, July, 1989.  相似文献   

15.
1.  The adopted design and construction schemes for the dam made it possible to place, under complex geologic and hydrologic conditions, the dam fills without trench construction or drainage, which permitted starting sooner the fill placement work and sharply reduced the construction cost.
2.  For the dam engineering work, use was made of national and foreign experience in construction of high rock-earth dams -the dam core was constructed using clay-skeleton soil fills; the developed transition zones were made using fills consisting of inexpensive natural soils, which made it possible to eliminate the use of artificial mixes; and zoned placement of soils in the dam shells was carried out.
3.  The construction method and sequence made it possible to build the dam under complex climatic conditions within the established period and to use soils from useful excavations almost exclusively.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 6, pp. 12–16, June, 1991.  相似文献   

16.
1.  The arch dam of the Khudoni hydrostation can be constructed by the continuous conveyor technology as enlarged blocks.
2.  The rate of concreting the dam for the proposed dimensions of the blocks and times of covering them can reach 200–250 m3/h.
3.  To attain the indicated rate of concreting, it is necessary to construct near the dam site a new concrete plant with facilities for cooling or heating the concrete mix.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 8, pp. 13–14, August, 1990.  相似文献   

17.
1.  The construction ana operation of the upstream wing wall of the Tashkumyr hydroelectric station confirmed the possibility and expediency of using lean rollcrete and simple designs for dams. After 3 years' operation the wall is in a completely satisfactory state.
2.  The use of rollcrete with a cement content of 80–120 kg/m3 during concreting by the technology proposed and perfected during construction of the wall provided the obtainment of concrete grades M100180–M200180 (classes V7.5–V15). When designing rollcrete it is necessary to take into account its increased nonuniformity — the coefficient of variation of the strength values of the concrete of the wall was 0.20–0.25.
3.  A uniform temperature regime with low values of the maximum temperatures is characteristic for rollcrete masonry. The measured temperature of the wall masonry corresponded to those calculated. The possibility of predicting the temperature regime of the rollcrete mass during its construction is thereby confirmed.
4.  When designing hydraulic structures it is necessary to take into account the anisotropy of the density of rollcrete masonry. Horizontal joints have a high permeability, which requires either a special technology of forming them or structural protection of such masonry with the outer zones made of vibrated concrete. It is expedient to protect the rollcrete masonry with a gunite layer mainly for temporary dams.  相似文献   

18.
1.  A comparison of laboratory and on-site data on a determination of the maximum range of oscillations at the end of a direct hydraulic jump when waves enter it from a chute with the results of calculations by theoretical formulas (1), (2), and (3) confirms the applicability of one of these formulas (2) for superrapid flow and flow transitional from superrapid to rapid.
2.  The stilling basin generates secondary waves, reaching half of the depth of the basin d with respect to its height. With submergence of the basin from the lower pool, the range of variations of the level increases additionally by 2.0–2.5 times.
3.  On the apron behind the stilling basin, the drop of waves is insignificant, since the wave transformation coefficient at distance (40–90)hn, where hn is the natural depth, remains equal to .
4.  The periods and lengths of the waves transformed in the stilling basin decrease with increase of discharge and Froude number Fr0 and approach in value the wave periods.
5.  Formulas (6) and (10) were obtained for calculating the maximum amplitude of oscillations of the free surface and maximum depth at the crest of oblique waves on the narrowing sections of the wave chutes and they were checked experimentally, which proved the applicability of these formulas for calculating a nonstationary oblique hydraulic jump.
6.  The proposed empirical formulas (12)–(17) can be recommended for an approximate evaluation of the parameters of the largest first waves on the narrowing stretch.
7.  Under these conditions, the use of a stilling basin as an energy dissipator of a superrapid flow is not rational, since not dissipation but generation of secondary waves is observed in it. When designing narrowing sections of chutes, it is necessary to take into account an increase of depth of the oblique jump with passage of roll waves.  相似文献   

19.
1.  Modified wood is an effective substitute of the laminated wood lining of bearing bushings for vertical pump units.
2.  An investigation of modified wood showed that this material in some indices (friction coefficient and wear resistance) is better than laminated wood.
3.  Since there is no mass manufacture and centralized supply of modified wood, it is possible to create a technological department for its production.
4.  Organization of the department does not require capital expenditures and special accommodations.
5.  Machining of the wood is performed on ordinary metal-cutting machines with the use of the tools used when machining laminated woods.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 7, pp. 33–35, July, 1991.  相似文献   

20.
1.  Absorbing formwork has a substantial effect on concrete quality for concretes with W/C0.365.
2.  The concrete surface quality depends on the quality of the absorbing formwork materials used.
3.  The possible amount of water removed from the concrete by means of the absorbing (vacuum) formwork was 2.4–3.57 kg/m2.
4.  Before the start of hardening of the concrete, its water content decreases by 20–30% at a depth to 15 cm from the absorbing formwork. During hardening of concrete, its water content equalizes over the entire length of the specimen (thickness of the block), and under these conditions the W/C ratio of the concrete near the formwork is not more than 1% below the initial.
5.  According to the results of testing the concrete for cavitation resistance, the best indices were noted for formwork containing ensonite. In this case, the cavitation resistance of the concrete was increased up to 1.4 times. The latter circumstance permits recommending for use as formwork absorbing material fine-porous paperboard of the ensonite type (with pore sizes 20–100 Å), which freely passes water molecules but retains cement particles.
Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 39–41, November, 1989.  相似文献   

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