In 1973, the Central Asia Branch of the S. Ya. Zhuk All-Union Scientific-Research and Design-Investigation Institute of Hydrotechnical Construction (Gidroproekt) commenced work on the development of an engineering-economic basis for the Kambaratin hydroelectric scheme on the Naryn River, with a capacity of 2000 MW.The principal and most important structure of the hydropower scheme is a high ( ~ 300 m) dam to be constructed of rockfill placed by directed blasts.Also, as distinct from normal designs, it is not proposed to provide special antiseepage zones in the Kambaratin Dam.The unique nature of the structure, the specific features of its construction and method of carrying out the work, and the absence of sufficient experience in the construction and operation of such structures necessitated carrying out an extensive program of investigations, including trial blasts modeling placement of the dam under full-scale conditions.The main questions investigated were: a more accurate determination of the design functions for the parameters of the massive blast; a study of the geotechnical and seepage-piping properties of the blasted rock fall, and development of methods for their prediction; an assessment of the blast effects on the preservation of the parent rock mass, on the structures of the hydropower scheme, and on industrial establishments in the surrounding area.

Development of the water resources of the Chirchik River in the Uzbek SSR, the main tributary of the Syt~darya River in the middle course, is being accomplished by constructing a cascade of Middle Chirchik hydroelectric stations.Xn 1941 the construction of the diversion works of the Chlrchik (Tavak and Komsomol) hydrostations made it possible to divert waters of the Chirchik to the Boz-Su waterway and to construct on it by 1954 a cascade of 16 hydrostations with a total capacity of 320 MW. The upper course of the Chlrchlk remained unused for a long time.The cascade of Middle Chirchik hydrostations (Fig. I), consisting of three--Charvak, Khodzhikent, and Gazalkent --using the drop of the upper course of the Chirchlk and mouth reaches of the Chatkal and Pskem rivers over a length of 45 km to the diversion works of the Chlrchikhydrostatlons with a total drop of 215 m. Below the confluence of the Chatkal and Pskem rivers the Chirchlk flows into the Charvak Gorge, where the Charvak hydrostation has been constructed. Below there the Chirchikvalley has a gorge structure and the river flows in a narrow rocky canyon up to 40 m deep cut into the Intermontane valley. Within this stretch the Khodzhikent hydrostation has been constructed and the Gazalkent hydrostatlon is under construction. The average slope of the rlverln this stretch is 3.2 m/km.Within the stretch being considered one comparatively large tributary, the Ugam River, accounting for 9% of the total runoff of the Chlrchik, and several small mudstream tributaries (KaranJul'sal, etc.) empty into the Chlrchik from the right below the site of the Charyak hydrostation. The normal runoff of the Chlrchlk at the site of the Charvakhydrostation is 6.5 km s and at the sites of the Khodzhikent and Gazalkent hydrostations 7.2 km3; 80% of the annual runoff passes in the s,,--,er (April-Septomber).The average winter natural discharges at the site of the Charvak hydrostation are 70-80 mS/sac and at the Khodzhlkent and Gazalkent hydrostations 75-85 mS/set. The maximum observed discharge at the Charvak hydrostation is 1600 mS/sec and at the Gazalkent hydrostation 1960 mS/set. The annual sediment discharge of the Chirchlk under natural conditions at the Charvak hydrostation is 2.9 million tons, and of the Ugam River about 0.3 million tons, which determine the long period of silting of the dead storages of the reservoirs, viz., Charvak about I00 years, Khozhikent and Gazalkent more than 50 years.The structures of the Charvak hydrostatlon are of the first class and of the Khozhikent and Galzalkent of the second. For the Charvak hydrostation the maximum design flood discharge for extreme operating conditions with a probability of 0.01% is equal to 2400 me/set. With consideration of storage of part of the runoff in the reservoir the design discharge of the structures is 2150 mS/sec. The surplus flood works for the construction period were calculated for discharges with 1% probability of 1410 mS/set (the increased probability was used in connection with the fact that the structures we...

One of the most widespread typesofdam adopted in the construction of hydropower schemes in mountain regions is the rockfill dam built from local natural materials. For dam heights of the order of 250-350 m, the fill volumes become very large (50-120 million m s) and the construction of such hydropower schemes requires very high capital and labo~ inputs. For these dams the problems of reducing the cost and time of construction have not been wholly solved. Therefore, the development and application of fundamentally new and progressive design and construction technologies for high earth and earth-and-rockfill dams must become the principal trend in dam construction in mountain regions. In the construction of dams from local materials the following two stages stand out [1]:Stage I. Foundation preparation, which is accompanied by the driving of diversion tunnels and construction of cofferdams, dewatering of the river bed, cleaning the excavation on the area of contact between the foundsdon and the water-retaining elements of the dam (core or membrane), and blanket and curtain grouting.Stage 1I. Construction of the dam prism, including work on the winning of materials from quarries, the mechanical processing of material suitable for placement in the water-retaiuing elements of the dmaa; transport of the excavated and processed materials from quarries and plant to the dam; and the dumping, spreading, and compaction of the various materials in the dam prism.The execution of the above-mentioned interrelated works, where the dam dimensions are increased and the construction operations are shifted deep into mountainous regions, is rendered substantially more complex owing to the difficult access conditions in narrow gorges. The steepness of the slopes complicates the development of quarries for the dam rockfill, and the substantial distance of the loam, gravel and sand borrow pits from thedamsite gorge, located in the main rock massif, give rise to high haulage costs. The difficulties are aggravated immeasurably by the low capacity of modern transport equipment in comparison withthe growing volumes of dams. Furthermore, the construction of a high rockfill dam of traditional type necessitates the driving of a large number of special transportation and auxiliary tunnels and various types of shafts, whose total length together with the hydraulic tunnels can amount to 35-40 km (e.g., at the Nurek and Rogun hydropower schemes). The combination of these factors causes a marked increase in the length and complexity of the communication services, the fleetsofmechanical and service plants, the number of personnel, the volume of design work for items in the work areas and the township.The unfavorable effect of the above-mentioned factors is markedly reduced where dams are constructed by directional blasts. This method, which is the most expedient under poorly accessible, mountainous conditions, enables large economies to be effected by a single heave of the whole voktme of construction material into the dam prism by means of explosiv...