Kopyshev ]IDC 666.971.4The semiautomatic PTsU-2 grout preparation plant, designed by the State Institute for Specialized Operations of the All-Union Planning, Surveying, and Scientific-Research Institute (Gidrospetsproekt) was used up to 1970 for grouting works in hydraulic engineering (Fig. 1).The grout unit made it possible to prepare any working grouts and pump them into boreholes within a radius up to 200 m from the place of its installation. Among the shortcomings of the PTsU-2 are its large size and low output (it takes up to 20 min to prepare one 0.75-m 3 portion of working grout).At the construction of hydroelectric stations with a small amount of grouting works (Bratsk hydrostation 40,000 m, Krasnoyarskhydrostation 137,000 m, etc.) under conditions of spacious sites the plant provided grouting of the objects within the established times.However, in connection with the movement of hydropower construction into mountainous regions and the need to construct high dams the requirements imposed on the quality of the rock foundation increased.The volume of grout injection works increased severalfold (Nurek hydrostation 440,000 m, Ingurl hydrostation about I million m) with an overall shortening of the time of these works.Hydropower complexes being constructed in mountainous terrain are characterized by an underground arrangement of the transport schemes and hydraullc-englneering installations. For instance, the length of all tunnels, chambers, and inclined and vertical shafts at the Nurek hydrostation reached 35 km and at the Rogun hydrostation 70 km. Under these conditions the accomplishment of crack-seallng grouting of tunnels is a serious problem.The use of the PTsU-2 or analogous grout units at such construction sites (Fig. 2) required: complete readiness of the underground workings and transport schemes for grouting; the creation of a large number of additional underground chambers for setting up the grout units with stores of materials, and also additional tunnels for vehicular traffic; solution of the problem of removing cement dust from the air of the underground workings during loading and unloading operations; setting up an efficient system of supplying cement to all grout units.

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