No abstract

No abstract

Editor's note. As was already reported, the expediency and possibility of locating at the site of the Dnepr hydrodevelopment a second powerhouse with eight units having a total capacity of more than 800, 000 kW was established as a result of design work and water-management and energy economic calculations. Presently six units are operating at the Dneprog~s-II station, construction of the station is being completed, and construction of the new ship lock is proceeding at full speed. In view of the specific conditions of the construction of this station* the designers and builders made a number of new decisions both in designs and in technology of construction work. For purposes of study and popularization of the experience gained in constructing Dneprog6s-II the editor of this journal has organized the composition of a number of articles by designers and builders. N. V. Shekhtman, chief engineer of construction and director of the correspondent's post, has and is participating actively in organizing this material for which the editor expresses great thanks. The first selection of articles on the experience of constructing Dneprog6s-II is being published in this issue of Hydrotechnical Construction. One of the most important problems of modern construction lies in the acceleration of the rate and the reduction of the cost of concrete work. At the Dneprog6s-II hydroelectric plant, now under construction, the solution to this problem has its own characteristics, determined by the specific aspects of the construction work, the constructional features of the structures, and the properties of the matetials for preparation of the concrete. The extremely limited design sections of the structures at the Dneprogds-II plant, require, in comparison with the Dneprog6s-I plant,-high classes of concretes as regards strength and impermeability. The presence of sulfate aggression from ground water in the lock zone leads to the need for limiting the water--cement ratio and for using sulfate-resistant cement. Moreover, the aggressiveness is complicated by an absence of laws governing its distribution. The lack, at the construction site, of sand of sufficient coarseness makes it necessary to use fine Dnieper sand for preparing the concrete. The granite gravel brought tothesitefrom the Zaporozhe quarry is, as a rule, unsatisfactory for obtaining concrete wifll a highly impervious grain composition, since it has a broken grain-size distribution with a predominance of coarse fractions and an insufficiency of fine components. Another defect of this gravel lies in the presence, on the surface of its particles, of a rock dust film which lowers its adhesion with the cement and reduces the impermeability of the concrete. All this calls for the use of large quantities of cement and causes the cost of the concrete to increase. For this reason the main problem of the constructors of the Dneprog~s-II plant, as well as of the designers of the Ukrainian Branch and the Scientific-*A description of the hydrodevelopment and the specific characteristi...

No abstract