Technology of manufacturing precast reinforced-concrete elements of the penstocks of pumped-storage stations

Abstract

The problem of manufacturing precast reinforced-concrete elements of penstocks with an inside diameter of 7.5 m for a design pressure of 1.7 MPa was solved in the USSR for the first time and, naturally, challenged designers with a number of problems.As a result of generalizing foreign and Soviet experience in the manufacture of pressure pipes it was decided to use the unit-line method. With consideration of the dimensions and mass of the precast reinforced-concrete element and the limited number of elements being manufactured for a particular pumped-storage station (PSS) in a construction period lasting 3-4 years, it was decided to manufacture the precast reinforced-concrete elements under casting yard conditions in an open area.Work on designing the mechanized technological line necessitated solving the following main problems: method of casting the elements; method and regime of compacting the concrete mix; selection of the composition of the concrete; method of heat treatment and the thermal regime; organization of works on anticorrosion coating of the inside lining of the conduit; possibility of combining the process of maturing and anticorrosion works to shorten the manufacturing cycle; method of quality control of the articles; creation of an industrial experimental casting yard at the construction site of the Zagorsk PSS; creation of nonstandardized equipment for the yard; debugging of the equipment and improvement of the technological processes under production conditions. The All-Union Planning, Surveying, @nd Scientific-Research Institute (Gidroproekt), research department of Gidroproekt, mechanical department of the special design bureau of Gidroproekt, and alsothe Moscow Special Design Department for Steel Hydraulic Structures (Mosgidrostal') and the All-Union Trust for the Protection of Power Equipment (Soyuz~nergoza-shchita) participated in solving these problems.Considerable work on the part of the research department of Gidroproekt preceded the selection of the main technological solutions regarding the compositions of the concrete and method of heat-treating the elementS.The choice of the unit-line method of manufacturing the precast elements was dictated by the need to cast the element at one or two stations with further transfer of the cast article to the maturing station. The casting station is a resonance platform vibrator having a load capacity of 200 tons with horizontal circular vibrations.The metal formwork with the reinforcement frame and lining wrapped on the molding drum is placed vertically on the platform vibrator.The reinforcement frame is made at a special yard and hauled in a finished form to the casting station.The concrete is placed by 3-m 3 bucketsby means of a 10-ton-capacity gantry crane with delivery of the concrete into themoldthrough a special distributing device. The total volume of concrete in the element, 48 m 3, is placed in four layers with a height of i.i m each. The concrete mix is compacted during unloading of the buckets. After placing the last bucket the distribu...