CONSTRUCTION OF THE ARAKS HYDRAULIC DEVELOPMENT

N. A. P u r y g i n a n d I~. A. K a n e v s k i i UDC 627.8.65.011.4(47+57)

The Araks hydraulic development and the Mii'-Mugansk dam, which are located on a main railway along the Soviet bank, were constructed in the frontier zone of the Araks River, at a distance of about 270 km from each other, along uhe river. At the places where these hydraulic developments are located, the river has wide flood plains, which are adequate for accommodating the subsidiary enterprises and the construction camps.

Construction Facilities (Figs. 1 and 2). In connection with the short construction periods, it was necessary to minimize the length of the preparatory period. This was possible thanks to the accommodation of all the sub- sidiary enterprises and plants in precast-demountable buildings, assembled mainly from Departmental Unified Typ- ical Sections (VUTS). The production of these sections was the responsibility of the Kaunassk Combine of Subsidiary Enterprises of the Ministry of Power and Electrification of the USSR (Mindaergo). Thanks to this solution, the prep- aratory period was reduced to less than one year. In addition, new techniques were quickly adopted at the con- struction site, owing to the excellent conditions created there. Unified typical sections were used not only for the production enterprises but also for the residential units and, in particular, for the dubs in the construction camps. However, permanent buildings were constructed for other purposes (mess halls, administration buildings, and other minor buildings).

The construction personnel were independently housed by each of the parties. Permanent dwellings for the Soviet workers and specialists were constructed in the newly-developed areas of nearby cities, from which the workers were transported by buses and rail to the construction site. Comfortable temporary settiements, constructed

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\ USSR rran

Fig. 1. The Araks hydraulic development. 1) Construction facilities; 2) earth dam; 3) powerhouse (Iran); 4) powerhouse CUSSR); 5) concrete plant; 6) stone pit: 7) rabble pit: 8) gravel pit: 9) loam pit; 10) gravel-sand pit: 11) construction area: 12) temporary living quarters.

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 10, pp. 11-13, October, 1972.

932

CONSTRUCTION OF THE ARAKS HYDIIAULIC DEVELOPMENT 933

USSR [ ///7 I Iran

/

Fig. 2. The Mil '-Mugansk dam. 1) Construction facilties| 2) pit for concrete structures; 3) water-supply canal; 4) annular cofferdam; 5) provisional highway bridge; 6) gravel pit; 7) loam pit; 8) construction area.

TABLE I

Type of work

Excavation, thousands ofm s earth . . . . . . . . . . . . . rock . . . . . . . . . . . . .

F i l l thousands of m s "s " Concret~ thousandsof m

Araks hydraulic development

! 500 340

2 lO0 200

Mil' - Mugansk dam

620

I 100 65

by using GPD stock demountable houses of the block type, were created on the Soviet side of the construc- tion site; hostels for the workmen and cottages for the specialists were built on the Iranian side.

Diversion of River Flows during Construction. The schemes for diversion of the flows during con- struction were determined in different ways for the two hydraulic developments, depending upon their location with respect to the river. At the Araks hydraulic development, which has a flood-plain arrangement of the concrete Structures, the flows

were diverted under normal conditions during the initial construction period, and the the concrete structures were constructed under the protection of low cofferdams. At the Mil ' -Muganskhydraulic development, which has a fiver-channel arrangement of the structures, the flows were diverted through a water-supply canal located on the right bank, and the pit for the concrete structures was protected by an earth cofferdam. Subsequently, in both cases, the flows were diverted through conduits in the concrete structures, with the difference that at the Araks hydraulic development this was done in 1969 for the purpose of passing the second flood since the start of construction, while at the Mil'-Mugansk hydraulic development it was done only in 1970 after the passage of the usual flood.

934 N~ A. PURYGIN AND ~-. A. KANEVSKII

The design flood, with a ~o frequency, was determined as 1260 mS/sec for the Araks hydraulic development, and as 1430 mS/sec for the Mil'-Mugansk daml with a 1~ frequency, it was determined as 1650 mS/sec and 1830 mS/sec, respectively, for the two projects. In 1969, there was an exceptionally large flood, which exceeded all previous records. At the Araks site, this flood was passed through the conduits in the uncompleted concrete structures, and at the Mil'-Mugansk site it was passed through the water-supply canal. The conduits in the uncompleted concrete structures at the Araks site were not sufficiently large for passing such a flood; for this reason, the upstream water level rose considerably, and the water flowed over the concrete structures and inundated the pits. All the structures withstood satisfactorily this catastrophic flood, but flooding of the pits caused considerable damage and delayed the concreting work for 1.5 months, owing to the need for drying out and cleaning the pi ts .

At the downstream development, the floods were more favorably passed. Only a few spans of a temporary highway bridge across the water supply canal were destroyed as a result of erosion at the supports. The communica- tion between the banks was maintained for a short period by using a helicopter. The earth cofferdam around the pit did not suffer any damage. It should be pointed out that at the Mi1'-Mugansk hydraulic development wide use was made of gabions for protecting the cofferdams and dikes. These gabions were filled with stone as well as with gravel.

At both sites, the river was dammed by the pioneer method during the low-water period, when the flows were on the order of 200 ma/sec. The damming operations were begun by placing gravel dropped from the banks so as to form a narrow passage; later, a rock m a s s was placed; and in the final stage, the constructors dropped the massive concrete blocks into the river.

Earth-Rock Work. At the MiF-Mugansk development, the earth excavation work was carried out by using -1252 excavators in conjunction with MAZ-503V dump' trucks. In view of the high water table, the soil excavat ion

in the pits for the structures and in the quarries was carried out by excavators - a backhoe and a dragline excavator.

The volume of basic work at both hydraulic developments is shown in Table 1.

At the Araks development, the soil in the pits for the structures was excavated by r -1252 and r -2503 ex- cavators and the material was carried away by MAZ-503V and KrAZ-256 dump tracks. The same types of ex- cavators were used at the quarries, where use was made also of BelAZ-540 dump trucks, in addition to KrAZ-256 dump tracks, for transporting the soft. At the pits for the structures, the drilling-blasting work was carried out by using perforation and percussiou-rotary drilling, and smooth blasting. The pits for the structures were dried out by means of portable centrifugal pumps mounted on C-569 and C-666 cars. Self-powered scrapers were used for ex- cavating the topsoil in the quarries and part of the soft soils in the pits.

The soils in the body of the dam were compacted by D-551A, 38-ton self-powered wheeled rollers.

It should be pointed out that for the outer rock toes of the earth dam at the Araks site use was made of a somewhat unusual material consisting of rabble-gravel soil with a loam filler, a source of which was discovered in the immediate vicinity of the right-bank dam abutment at the upstream side. Special investigations conducted on this soil revealed its suitability as a material for the rock toes, and its adequate content of loam filler permitted discarding the construction of transition zones between the loam core and the rock toes.

Concreting Facilities. The concreting facilities at both sites included stock, single-section, cyclic action concrete plants with 1200-1iter mixers at Araks and with 500-liter mixers at Mil '-Mugansk; 2400-ton and 720-ton standard rail-mounted cement storehouses consisting of steel bins; 30000-m s and 2500-m s stock aggregate tanks, admixture-handling machines, and compressors.

The concreting facilities at Araks included also a gravel-sorting installation with an output of 200,000 m s per year, which processed gavel -sand material from the local quarries. The facilities were located on a site in the immediate vicinity of the left-bank structures. The gravel-sand material was obtained from a flood plain of the Nakhichevanchai River, located at a distance of 5 km from the construction site.

The relatively small volume of concrete placed in the hydraulic development and the existence of a construc- tion-materials plant at a distance of 64 km from the gravel pit favored the construction of the concreting facilities for this project in the area of the constmctiou base, that is, in the vicinity of the railways. Part of the gravel was graded by movable installations. In both developments, the aggregates were transported by stack conveyors from the places of storage to the concrete plants, and the cement was air-transported at the Araks site and mechanical ly at the Mugansk site.

CONSTRUCTION OF THE ARAKS HYDRAULIC DEVELOPMENT 935

The regular concrete was produced mainly from Grade BGT-200 gravel, while the wear-resistant concrete was produced from Grade BGT-400 imported rubble and from sulfate-resistant as well as from ordinary cement. The monthly volume of concrete placed was 15000 m s at the Araks plant and 6000 m 3 at r_he I~l '-Mugansk dam. It was placed by crawler-mounted and tower cranes using 1.6-m s and 3.2-m s buckers, as well as directly by dump trucks.

The constructors used panelled wooden and metal forrnwork. Five different types of metal formwork panels, which had a common height of 2 m, were used. They were suspended from the reinforcement cages and secured to the joints by means of special clamps and connected to each other by means of bolts.

During the winter, with atmospheric temperatures of-15~ the concrete was placed by the "thermos" method, in a heated wooden formwork with its horizontal surface covered by sacking or mars and sawdust filling (for blocks with a formed-surface coefficient of up to 0.5). When the atmospheric temperatures reached -5~ the water was heated to 75-80~ The steel reinforcement, in the form of welded wire fabric, bundles, and load-bearing cages, was prepared at the site.