Because of the wide development at the present time of highly mechanized methods of compaction, the problem of the quality of horizontal construction joints arouses great interest. The current -Technical Rules for Hydraulic Engineering Work" stipulate the placing of an underlying layer of cement mortar or of fine-grained concrete on the surface of the hardened block prior to placing fresh concrete. This technique, developed from long experience with construction of hydraulic structures in which the concrete was compacted by hand-held vibrators, makes it necessary to increase the quantity of cement and complicates and raises the cost of the construction work. As shown by previous experience, the use of intense vibration permits concreting hydraulic structure block without the need for placing an underlying layer of new concrete. By this means the construction of the dam at the Toktogul hydroelectric plant [12] is being suceessfuUy carried out. Experience with cons=uction of the Dworshak dam in the USA [13] also supports the advantages of this method. However, these techniques have not yet been formalized in normative documents.In this connection, at the Laboratory of Vibration Techniques of the 13. E. Vedeneev All-Union ScientificResearch Institute of Hydraulic Engineering (VNIIG) and at the Sayano-Shushenskoe hydroelectric plant, analyses were made of the available experimental material from studies of the quality of the bond between new and old concrete, and special tests were designed for investigating the quality of the joints obtained by applying different concreting techniques. Table 1 presents the bond strength indices for new and old concrete according to published data. They indicate that the results of tests on the relative strength of joints, obtained by many investigators over a long period of time for different compositions of concretes, agree sufficiently satisfactorily on the whole.The mean value of the relative bond strength (with respect to monolithic concrete) was 0.63 without an intermediate layer of mortar and 0.68 with it. In addition, the uniformity of the relative strength, characterized by the coefficient of variation, was higher for the samples prepared by placing an intermediate layer. In this case, the coefficient of variation was 16.4%, whereas for samples made without intermediate layers it was 23%. One of the possible causes of such nonuniformity is the insufficiently intense compaction of the mix in the contact layer, which was not considered in the tests. In order to take into account this important construction fact, which affects the formation of the contact joint, material was gathered from full-scale tests, and investigations were carried out with Fig. i. General view of stand for water-absorption tests. 1) Tank of compressed air; 2) reducing valve; 3) flexible highpressure hoses; 4) tank of water; 5) pressure gauge; 6) weights; q) tube with seal; 8) test block.

In hydrotechnical construction, any concrete with a strength exceeding 400 kg/cm z is classed in the highstrength category. However, various technological difficulties are encountered during the manufacture of highstrength concrete* in plants equipped with large-capacity (1200-2400 liters) concrete mixers. This problem can be solved by the use of highly active quick-setting cement, high-quality homogeneous fractionated fillers, and hard concrete mixes with a minimum water content. Another important factor is the development of suitable processes for the preparation and thickening of concrete mixes which wouid yield the desired homogenization to ensure the stmcturization of cement blocks. The conditions cited for the production of high-strength concrete are not applicable to monolithic concrete due to the inevitable increase in heat evolution limiting the flow rate of cement.Scientifc literature offers relatively little information on the manufacture of high-strength concrete in hydrotechnical construction plants despite the fact that considerable success has already been achieved in the selection and preparation of concrete with a strength of 400-500 kg/cm z under industrial conditions. Unlike the highstrength concrete used in sectional reinforced-concrete structures, hydrotechnical construction requires the manufacture of this concrete under normal-humidity setting conditions. Furthermore, the addition of complex admixtures which activate setting is restricted due to the need for preparing large volumes of concrete in plants and to the difficulty in maintaining high accuracy when measuring out the admixtures.High-strength concrete employed in hydrotechnical construction can be divided into two types by solidity: 1) relatively thin concrete, used for the ground ports and lining of water-carrying tunnels and spillways, draft tubes; 2) heavy concrete, used in preparing blocks for arch dams, for structures in the vatiable water level zone with high frost resistance (300 and up), and for other purposes. In all cases, however, experience has shown that the utilization of cement type 400-500 with an activity not less than 450 kg/cm z and water consumption not exceeding 26% is absolutely necessary to ensure a concrete strength of 400-500 kg/cm z. Accordingly, the manufacture of highstrength thin (or light) concrete requires the use of cement with a high allte content, e.g., 55-65% C3S and sometimes even higher. In the latter case, concrete type 400 and higher containing multifractionated fillers may be prepared at a relatively moderate rate of cement consumption.The use of high-aNte cement in manufacturing heavy concrete for hydrotechnical construction markedly complicates temperature control processes during concrete setting, therefore this particular cement is not always recommended despite the reduction in cement content. As a rule, the alite content in cement for heavy hydrotechnical concrete is limited to a maximum 48-50% which can only be ensured at certain cement manufactutin~ *0. Ya. Berg et al, define high-stre...

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A unit of the Sayano-Shushenskoe hydropower project is an arched gravity dam 245 m high with a crest length of 1066 m and a base width of 105.7 m. The dam consists of four parts: a spillway segment with 189.6-m crest length, power station 331.6 m long, and the two abutment blocks.The spillway part, with ii orifice outlets, is designed to discharge 13,500 m3/sec and is located near the right bank. The operational spillway orifices are serviced by two radial gates working under heads of up to 107 m. Energy dissipation of the flow, whose velocity at its exit from the spillway face reaches 50 m/sec, is effected in a stilling basin 144 m long and 130-110 m wide, with a water depth of about 44 m upstream of the end sill. The stilling basin of the Sayano-Shushenskoe hydropower project, in regard to its dimensions and the problems of dissipating the huge quantities of energy in its high-velocity flow, is a unique structure, and has no equal in the world's hydrotechnical construction practice.