elevation of 127 m. achieved.

In this case a substantial acceleration of returns on investments is

On the basis of the aforesaid the variant with the Middle Enisei hydrostation at the Aba!akovo site with a NPL of 127 m is recommended in the scheme. The recommended variant of the scheme includes two hydrostations: the Middle Enisei at the Ahalakovo site and the Lower Angara at the Shivera Kosaya site. The main parameters of these hydrostations are given in Table 4. An expert commission of the USSR State Planning Commission examined the materials of the scheme of using the Middle Enisei and Lower Angara and approved its main points.

HYDRAULIC EXCAVATION IN THE WINTERTIME IN SIBERIA Yu. A. Popov, B. V. Sadlei, and L. F. Dzyubenko

UDC 624.132.345

The economic development of Siberia is accompanied by a considerable increase in the volume of earthworks performed by the hydraulicking method. The main premises permitting the statement that already in the near future it will gain wide development in northern and eastern regions of the country are: the higher productivity and degree of mechanization of technological operations and processes compared with other methods of performing earthworks; the solvability, in principle, of all scientific~ technical, and practical problems due to the use of hydraulicking under complex natural-climatic conditions; the small degree of development and difficult accessibility of the regions of performing works, where the delivery of materials for constructing structures by other methods is difficult or even impossible; the accumulation of favorable experience in hydraulic filling of dams of a number of European and Siberian hydrostations under winter conditions. At the same time, the use of hydraulic excavation under conditions of Siberia is related to the need to increase the annual work load of the hydraulicking equipment. The solution of this important economic problem is presently being accomplished primarily by increasing the duration of the hydraulic-filling season by extending it in the fall and by an earlier start in the spring. The original block scheme of hydraulic filling of earth dams of Siberian hydrostations proposed by the State All-Union Trust for Planning and Performing Hydraulic Excavation Works (Gidromekhanizatsiya) of the USSR Ministry of Power and Electrification (Min~nergo) [i] opens wide possibilities for increasing the annual workload of hydraulicking equipment by using highly efficient organizational and technological schemes of performing works. The use of the block scheme is also prospective for constructing other types of structures. Scientific investigations [2, 3] and practice of performing hydraulickin~ works in the wintertime [4] proved that the maximum effect is attained when the natural heat stored in the soil of borrow pits and water of water bodies is efficiently used for increasing the hydraulic-filling season in the traditional scheme of works. The technoloo~y of a limited water body most fully corresponds to this principle. Its essence (Fig. I) consists in cutting off the working face of the dredges from the river and converting it to feed by warm groundwater. S u c h a scheme of organization of works was used during the two-levelexcavation of the pit for the lock of the Volga-Lenin hydroelectric station [5]. It was most fully perfected on an industrial scale at the Ust'-Kamenogorsk quarry. In this case the Krasnoyarsk construction administration of Gidromekhanizatsiya of Min4nergo in collaboration with the Novosibirsk branch of the All-Union Scientific-Research Institute of Transport Construction developed a method of calculated substantiation of the size of the excavated areas and time of closing the connecting cut [6] which permits increasin~ by almost 1.5 times the time of hydraulic filling of stockpiles of construction materials (sand-~rave! mixture) with an annual savings of 40,000 rubles per dredge of the 350-50L type. It can he hoped that in view of the indisputable advantages, such technology will ~ain wide use in Siberia. Translated from Gidrotekhnicheskoe Stroitel'stvo, No. II, pp. 5-7, November, 1985.

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9 1986 Plenum Publishing Corporation

573

Fig. 1, Diagram of maintaining the level of the working face by means of warm groundwater: AH) Lowering of water level; Q) water discharge of dredge and inflow of groundwater during a steady pumping regime. +=+-60C

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Fig. 2. Diagram of operation of dredges (1-4) during block hydraulic filling of structures: T,) Hydraulic-filling season during construction of fragment A; T~) same during construction of fragment B; T3) period of synchronous operation of dredges l a n d 2 on fragment A and of dredges 3 and 4 on fragment B; T~) operating period of all dredges; AT,) period of operation of all dredges on fragment A; ATe) same on fragment B. There is still another original principle in the technology of winter hydraulic filling of gravel, which is used by the Bratsk construction administration of Gidromekhanizatsiya of Min~nergo. The technology calls for washing out fine silt and clay particles with a size less than 0.15 mm. This leads to intensification of the process of water yield by the gravel stockpile and provides a loose state of the material at a negative air temperature. Control of the formation of ice in the working water areas of dredges (maintenance of an ice clearing) is one of the most energy-consuming auxiliary processes of winter hydraulicking. For this purpose new stream producers have been developed [7] which with respect to their indices surpass the best foreign specimens (Walmet, Fluches, and others). These units, producing water circulation at the working faces of dredges, maintain an ice clearing by using the deep heat of water bodies. By changing the principle of the three-dimensional design of the propeller blades in the new stream producers it was possible to increase by about 1.5 times the area of the zone of spreading of the met at the same power of the drive and to increase by about the same number of times the area of the ice clearing being maintained. The favorable experience of the industrial use of the indicated units in the Gidromekhanizatsiya Trust of Min~nergo (annual savings of 540,000 rubles) and in other departments proved the prospects of introducing the new design of thestream producers. The technological proposals of the V. V. Kuibyshev Novosibirsk Civil Engineering Institute [3] called for conducting winterizing works or the use of artificial heat sources (an electrical heating cable). Calculations substantiated the regimes of cutting away the thawed soll in the spring into an embankment, which accelerates by 3-5 times the process of thawing of seasonal frozen ground on the hydraulic-fill plots. The experience of using artificial snow in Canada for winterizing earth dams deserves attention [8]. 574

The block (alternate) scheme of constructing structures is the most promising in Siberia (Fig. 2). As a rule, within a particular object the field of operations of each individual or group of dredges is limited to a fragment of the entire structure (for example, to a block of an earth dam) or independent structure (for example, a sand or gravel stockpile). In Fig. 2 dredges i and 2 hydraulically fill fragment A of the earth dam and dredges 3 and 4 fragment B. According to the traditional scheme, all four dredges begin and end the hydraulic-filling season approximately synchronously and the duration of the hydraulic-filling season is T~ The block scheme calls for an earlier start of the season on fra~n~nt A but also its earlier end. The end of the hydraulic-filling season at a positive air temperature, when the water temperature at the working faces of the dredges has sufficiently high (+6 to +8~ values makes it possible: to achieve a considerable heat content of the soil of fragment A which is permeated by the infiltrating water during hydraulic filling; to provide intense water yield of the fragment after hydraulic filling ends. This gives rise to a favorable temperature and moisture regime of the soil, which, without detriment for the quality of the hydraulic fill, permitsstarting the hydraulic-filling season earlier. Dredges 3 and 4 in period AT, are switched to hydraulic filling of fragment A. The start of hydraulic filling of fragment B is specified at a later time, which provides natural thawing of the soil on the plots during period ATx. The latter circumstance permits extending the hydraulic-filling season beyond the summer. Dredges i and 2 during AT~ are switched to hydraulic filling of fragment B. The increased rate of hydraulic filling during AT2, which meets the condition of seepage stability, favorably affects the quality of placing the soil. Despite the obvious simplicity, block hydraulic filling makes it possible to increase by about 15% the annual workloadof the dredges compared with the traditional scheme of performing the operations. However, when constructing vital structures (earth dams of hydrostations) special attention is devoted to substantiation of the rational duration of periods ATx and ~T2 by method [3] and also to taking measures ensuring seepage stability during the construction period (until the annual construction of the supragelisol drainage system). The performance of earth works by the hydraulickingmethod in the wintertime is related, first, to complication of the works as a whole owing to ice and thermal difficulties at the working faces, in the pipelines, and on the hydraulic-filled plots; second, to the occurence of additonal technological processes and operations (winterizing works, formation and maintenance of an ice clearing, etc.). Therefore, despite the proved economic expediency of winter operations, their performance is justified only at enterprises and objects with a high production efficiency, where all other large potentials of hydraulicking have already been realized. It is expedient that the engineers, technicians, and workers be taught the method of economic evaluation of the time and volume of winter works and efficient methods of performing the works at a negative air temperature (at the facilities of the Department of Professional Improvement, V. V. Kuibyshev Novosibirsk Civil Engineering Institute). It is necessary to create an interdepartmental standard on the performance of hydraulicking operations under the harsh natural-climatic conditions of Siberia. LITERATURE CITED i. 2. 3. 4. 5. 6.

B . M . Shkundin and Yu. A. Popov, "Use of hydraulic excavation under harsh climatic conditions," Gidrotekh. Stroit., No. 3 (1979). B . M . Shkundin and Yu. A. Popov, "Calculation of the temperature regime of hydraulicfill dams during their construction," Gidroetekh. Stroit., No. 5 (1981). Yu. A. Popov, D. V. Roshchupkin, and T. I. Penyaskin, Hydraulic Excavation In the Northern Construction Climatic Zone [in Russian], Stroiizdat, Leningrad (1982). Yu. A. Popov and D. V. Roshchupkin, Wintertime Hydraulic Excavation [in Russian], Stroiizdat, Leningrad (1979). B . M . Shkundin, Dredging in Hydrotechnical Construction [in Russian], Vysshaya Shkola, Moscow (1977). Recommendation on the Formation and Maintenance of Ice Clearings Under Dredge Operating Conditions during an Extended Season [in Russian], TsNIIS, Moscow (1973).

575

7. 8.

Yu. A. Popov, V. V. Nikitin, and N. D. Yusha, "Investigation of the operation of stream producers," Transp. Stroit., No. 8 (1973). Bill Michaels, "Protecting Manic-3 against frost. Using snowmaking machines to cover till," Eng. Contract Rec., No. 2, 14-15 (1975).

TECHNOLOGY OF HYDRAULIC FILLING OF STRUCTURES FROM LOESSIAL LOAMS WITH INTENSIFICATION OF THEIR DEWATERING D, L. Melamut and R. Z. Utyaganov

UDC 624.132.345

Loessial foams having a high static and seepage stability are the most widespread local materials for constructing dams and embankments in Central Asia. The construction of structures from such soils is accomplished by the rolled-fill method with layer-by-layer wetting and ro11ing. In this case the cost of the works is high and moistening and the quality of placing the sol1 are nonuniform. The use of hydraulic placement of soils in structures eliminates these shortcomings. However, the use of loams for hydraulic filllng is limited by the duration of their consolldatlon process due to poor water yield. Therefore, the experience in hydraulic filling of structures from loams and measures on their compaction is of practical interest. The experience of constructing loam dams and embankments showed that these structures are usually hydraulically filled under the protection of shoulders placed from well-drainlng gravel and gravel--pebble materlal. Consolidation of the loam hydraulically filled between the shoulders takes years. However, the possibility of a failure due to the high pore pressure occurring in the structure is not precluded in this case. Also known are methods of one-slded hydraulic filllng of structures of a flattened profile which are free from these shortcomings and were used primarily on the construction of the majority of reservoir dams in the Turkmen SSR. In this case their use was limited to a 30-40% content of clay and silt fractions in the borrow soil. The positive characteristics of these methods are the layer-by-layer consolidation of the hydraulic fill, the formation of a shoulder, watertight facing, and wave-resistant upstream slope not requiring revetment. The main shortcoming is the large volume of soil being placed, as a consequence of which the height of the structure is limited to 15-20 m. However, in the case of hydraulic filling Of structures from loessial loams containing up to 60% silt and clay particles the size of the shoulder can be insufficient to provide stability of the structure and consolidation of the sol1 takes a long time. The use of such methods of intensifying dewatering as electroosmosls, electric drying, temporary drainage system, and others are ineffective or extremely expensive. The simplest method of dewaterlng hydraulically filled loam is to use natural drying, which is especially effective in Central Asia. However, with an increase of the thickness of the sol1 layer being hydraulically filled a long period is required as a consequence of the dense, overdried crust with a moisture content of disruption of capillary flow forming on its surface. Breaking of this crust restores the capillary connections for a certain time interval, which intensifies evaporation of moisture. A dry density of 1.49-1.52 tons/m s can be achieved as a result of using this method; in this case the size of the structure being hydraulically filled is limited to a height of 12 m. If necessary, a high density of the hydraulic fill can be obtained by its additional mechanical compaction at the optimal moisture content. Recommended Methods of Hydraulic Filling. On the basis of the results of investigations and an analysis of the experience of hydraulic filling of structures and methods of intensifying dewatering of hydraulic fill, a new effective method of constructing wide-profile structures from loessial loams was developed [i] (Fig. I). The essence of the method consists in using natural drying and moisture exchange for intensifying dewatering and compacTranslated from Gidrotekhnicheskoe Stroitel'stvo, No' II, pp. 7-11, November, 1985. 576

0018-8220/85/1911-0576509,50

9 1986 Plenum Publishlng Corporation