Filling of loams into water in a pioneer way. Regulations

SNiP 3.07.01-85

BUILDING REGULATIONS

HYDROTECHNICAL STRUCTURES

Introduction date 1986-01-01

DEVELOPED by the Institute "Hydroproject" them. S.Ya. Zhuk of the Ministry of Energy of the USSR (Ph.D. Tech. Sciences I.S. Moiseev - leader of the topic, Ya.K. Yankovsky, V.M. Braude, I.A. Ivanov, Yu.A. (Engineering Sciences A.E. Azarkovich, V.V. Kotulsky).

INTRODUCED by the Ministry of Energy of the USSR.

PREPARED FOR APPROVAL by the Glavtekhnormirovanie Gosstroy of the USSR (M.M. Borisova).

APPROVED by the Decree of the USSR State Committee for Construction of April 8, 1985 No. 47.

With the entry into force of SNiP 3.07.01-85 "River hydraulic structures", Section 1 in terms of river hydraulic structures and Sec. 2 SNiP III-45-76 "Constructions for hydraulic transport, energy and land reclamation systems".

These norms and rules apply to the construction of new, reconstruction and expansion of existing river hydraulic structures: concrete, reinforced concrete and earth materials dams, hydroelectric power stations, pumping stations, retaining walls, navigation locks, fish passage and fish protection structures - as well as structures for protection from floods, mudflows and ravines.

1. GENERAL PROVISIONS

1.1. When performing work on the construction of river hydraulic structures, in addition to the requirements of these rules, the requirements of the relevant SNiP Part 3 should be followed.

1.2. The construction of river hydraulic structures should be carried out with the involvement of specialized contracting construction and installation organizations that have the necessary special construction and installation equipment and equipment.

1.3. When reconstructing or expanding existing river hydraulic structures, construction work must be carried out by methods that ensure the safety of existing structures and underground utilities located in the construction zone and not subject to demolition.

1.4. The procedure for performing work on navigable rivers should ensure the safe, with the necessary intensity, the passage of ships and floating facilities during the construction period. The navigable sections of the water area in the places of construction and installation works must be equipped with signs of navigational fencing.

1.5. During the construction of river hydraulic structures, protection of incomplete and temporary structures or their parts from damage during floods, ice shifts, storms and squalls, wave action, piles and impacts of ships, floating craft and objects floating on the water should be ensured.

Schemes for passing river (ice) discharges through unfinished permanent ones, as well as through temporary river hydraulic structures, should be developed in the construction organization project (COP) and specified in the work execution project (PPR).

2. RECTIFICATION OF EMBIDS

FROM GROUND MATERIALS DRY

2.1. When erecting embankments from dry soil materials, in addition to the rules of this section, the requirements of SNiP III-8-76 must be met.

2.2. The construction of the embankment, preparation of the foundation and junctions with the banks should be carried out according to the technical specifications of the design organization, including the requirements for geotechnical control.

Immediately before laying the first layer of cohesive soils, the surface of the compacted base, as well as the surface of the compacted, previously laid layer, is loosened to a depth of at least 3 cm or wetted before laying the next one. The amount of water for wetting the surface is determined empirically.

2.3. To create a reliable contact between the core of the dam or the screen with the rocky base, it is necessary to thoroughly clean the surface of the base and prevent the accumulation of clods and large fractions of the soil dumped on the contact.

2.4. For dams erected from soil of inhomogeneous composition containing coarse-grained material in the form of inclusions, the PPR establishes the allowable size of these fractions, which should not exceed half the thickness of the backfilled soil layer in a compacted state. Fractions larger than allowed must be removed. The clastic material in the body of the embankment should be evenly distributed, without the formation of clusters in the form of nests and chains.

2.5. The thickness of the compacted layers, established by the PPR, should be specified based on the results of experimental rolling under production conditions.

2.6. In the construction of dams and dikes, the laying of soil should begin from lower places. During dumping, the soil is leveled with layers of a given thickness with a slope of 0.01 towards the downstream to ensure the runoff of atmospheric precipitation. When backfilling draining soils, the stacked layers must be horizontal.

2.7. The working area of ​​the structure being erected or its part (upper wedge, core, transition zone, screen, etc.) should be divided into horizontal maps, on which soil is sequentially taken in, the soil layer being laid is leveled and compacted in accordance with the PPR.

The dimensions of the maps when backfilling the impervious elements of dams are assigned depending on the intensity of backfilling of the soil and the outside air temperature. Separate cards must be mated with each other along a slope no steeper than 1:2.

2.8. During the construction of dams and dikes, consisting of several zones, backfilled in layers from different soils, it is necessary to take measures to prevent the ingress of soil from one zone to another.

2.9. Ponur can be constructed regardless of the time of laying the dam body. If there is a screen, the ponur must be erected to the device of the screen or its part adjacent to the ponur.

2.10. In dams with a soil screen, the thrust prisms should be erected ahead of time so that the laying of the soil into the screen is not interrupted until the end of its construction.

2.11. Screens made of clay or loam should be laid in horizontal layers with compaction to the required density. The surcharge of the erected part of the screen should be carried out with a lag from the filling of the screen by no more than 2 m in height.

2.12. The construction of dams from lumpy non-waterlogged clays should be carried out according to the specifications of the design organization.

2.13. When erecting dams with a central core having steep slopes (up to 10:1), the laying of soils of transition zones should be carried out while maintaining the angle of repose of the soil of transition zones and successively shifting the layers one relative to the other (herringbone laying).

2.14. Laying material in transition zones (filters) should be carried out in layers up to 1 m thick (in a loose state) with compaction by soil-compacting machines to the density required by the project.

2.15. During the construction of dams with soil screens and cores, the laying of transition zones, in order to avoid clogging of the filter material with soils of impermeable devices, should be carried out ahead of time, the value of which in each case is established by the WEP.

2.16. During the construction of rockfill dams, the thickness of the rockfill layers, backfilled using the pioneering method, is determined in the SDP, taking into account the filtration strength of the core and transition zones.

Backfilling of rockfill into rock-and-earth dams by layer-by-layer rolling should be carried out in layers up to 3 m, unless otherwise justified in the project. The accepted thickness of the layers must correspond to the technical capabilities of the compacting machines and mechanisms.

2.17. When dumping a stone into flowing water, the size and procedure for dumping should be established by the POS.

2.18. Specifications for the construction of embankments in the winter period of the year should contain additional requirements for the preparation, storage, transportation, laying and compaction of soil.

2.19. Backfilling of soils into the impervious elements of dams (ponur, core, screen, tooth) is allowed to be carried out at air temperatures up to minus 20 ° C, provided that the soil on the map is not allowed to freeze before compaction. Frozen clods are allowed no more than 15% of the volume of the poured soil.

Before laying soil on a frozen layer, the surface of this layer must be heated or treated with solutions of chloride salts. The thawing depth must be at least 3 cm.

2.20. To ensure the design density of the soil, the slopes of hydraulic embankments subject to rigid fastening should be backfilled with a widening of 20-40 cm along the normal to the slope (depending on the means used to compact the soil). Uncompacted soil from slopes should be removed and placed in the structure during its construction.

When fixing slopes by sowing grasses, riprap, gravel filling, etc. embankments should be filled without widening the design profile.

2.21. Loose soil from the mating surface of the slope of the previously erected part of the structure is to be cut to form a slope of 1: 4 and laid in the newly backfilled area. The surface of the slope, located normally to the axis of the structure, should have a broken outline in plan.

2.22. Control samples to determine the characteristics of the laid soil in the embankment of hydraulic structures should be taken according to Table. one.

Control samples should be taken evenly throughout the structure in plan and height, as well as in places where a reduced soil density can be expected.

2.23. When controlling the quality of the lateral prisms of the dam, made from stone in tiers, it is necessary to determine the density and granulometric composition of the stone, for which pits are torn off in each tier at the rate of one pit per 30 thousand cubic meters of laid stone.

2.24. Soil samples from the backfills of the sinuses of the foundations of hydraulic structures should be taken in accordance with clause 2.22, as well as at a distance of 0.2 m from the foundations.

Table 1

	Soil sampling method	Soil characteristics	The volume of laid soil per control sample
Clay and sand without large inclusions	Cutting ring, radioisotope	Density and humidity	100-200 cubic meters
			20-50 thousand cubic meters
Grave-pebble and fine-grained (with the inclusion of large fractions)	Pit holes (holes)	Density and humidity	200-400 cubic meters
		Grading	1-2 thousand cubic meters
		Other characteristics (for structures I and II classes)	20-50 thousand cubic meters

3. CONSTRUCTION OF EMPIDS BY THE METHOD OF FILLING SOILS INTO WATER

3.1. The method of backfilling soils into water is used for the construction of dams, dams, impervious elements, pressure structures in the form of screens, cores, droops and backfilling at the junctions of earthworks with concrete. For the construction of an embankment by dumping soils into the water and preparing a foundation for it and interfaces with the banks, the design organization must develop technical conditions, including requirements for the organization of geotechnical supervision.

3.2. The filling of soils into water should be carried out in a pioneering way, both in artificial, formed by embankment, and in natural reservoirs. Backfilling of soils into natural reservoirs without the installation of jumpers is allowed only in the absence of flow rates that can erode and carry away fine fractions of the soil.

3.3. Soil dumping should be carried out by separate maps (ponds), the dimensions of which are determined by the project for the production of works. The axes of the maps of the stacked layer, located perpendicular to the axis of the structures, should be shifted relative to the axes of the previously laid layer by an amount equal to the width of the base of the embankment dams. Permission to create ponds for filling the next layer is issued by the construction laboratory and technical supervision of the customer.

3.4. When filling an embankment into natural reservoirs and ponds with a depth of up to 4 m from the water's edge, the preliminary thickness of the layer should be determined from the conditions of the physical and mechanical properties of the soils and the availability of a dry soil reserve above the water horizon to ensure the passage of vehicles according to Table. 2.

table 2

Filling layer thickness, m	Carrying capacity of vehicles, t	Dry soil layer, cm, above the horizon water in the pond during filling
		sands and sandy loams	loams

The thickness of the backfill layer is adjusted during the construction of embankments.

At depths of natural reservoirs from the water's edge of more than 4 m, the possibility of backfilling soils should be determined empirically under production conditions.

3.5. The embankment dams within the erected structure should be made from the soil laid in the structure. Transitional layers or filters with screens on the inner slope made of impervious soils or artificial materials can serve as longitudinal embankment dams.

The height of the embankment dams should be equal to the thickness of the layer being poured.

3.6. When filling soils, the water horizon in the pond must be constant. Excess water is diverted to the adjacent card through pipes or trays or pumped to the overlying card by pumps.

Backfilling should be carried out continuously until the pond is completely filled with soil.

In the event of a forced break in work for more than 8 hours, the water from the pond must be removed.

3.7. Compaction of the dumped soil is achieved under the influence of its own mass and under the dynamic influence of vehicles and moving mechanisms. In the process of dumping, it is necessary to ensure uniform movement of vehicles over the entire area of ​​the dumped map.

3.8. When soil is transported by scrapers, dumping soil directly into the water is not allowed. In this case, the dumping of soil into the water must be carried out by bulldozers.

3.9. At an average daily air temperature of up to minus 5°C, work on dumping soil into water is carried out according to summer technology without special measures.

When the outside air temperature is from minus 5°C to minus 20°C, soil filling should be carried out according to winter technology, taking additional measures to maintain a positive soil temperature. Water in the pond must be supplied with a temperature above 50 ° C (with an appropriate feasibility study).

3.10. The sizes of maps when working on winter technology should be assigned from the conditions of preventing a break in work; backfilling of soils on the map must be completed within one continuous cycle.

Before filling the cards with water, the surface of the previously laid layer must be cleared of snow and the upper crust of the frozen soil must be thawed to a depth of at least 3 cm.

3.11. When dumping soil into water, the following should be controlled:

fulfillment of project requirements and technical conditions for the construction of structures by dumping soil into water;

compliance with the design thickness of the backfill layer;

uniform compaction of the surface layer of soil by moving vehicles and mechanisms;

compliance with the design depth of water in the pond;

the surface temperature of the base of the dump map and the water in the pond.

3.12. Samples to determine the characteristics of soils should be taken one for every 500 sq.m of the area of ​​the poured layer (underwater) with a thickness of more than 1 m - from a depth of at least 1 m, with a layer thickness of 1 m - from a depth of 0.5 m (from the water horizon to pond).

4. STRENGTHENING SLOPES OF EARTH STRUCTURES AND

SHORE PROTECTION WORKS

4.1. During the construction of canals and the construction of embankments of river hydraulic structures, the strengthening of slopes and banks should, as a rule, be carried out dry.

4.2. Reinforced slopes and banks should be pre-planned in the surface part, and in the underwater part - to be swept, cleaned and, if necessary, planned.

The layout of earthen slopes and banks in the surface part is carried out in accordance with the requirements of SNiP III-8-76. Underwater slopes are planned by cutting or backfilling non-cohesive soils.

4.3. The deviation of the marks of the slope edge for rigid fastening from the project is allowed ± 5 cm.

Deviation of the above-water slope surface from the design line after cutting off uncompacted soil and leveling is allowed ± 10 cm. The leveling accuracy is determined using templates and sighting by pegs installed 20 m along the slope, or instrumentally.

4.4. The treatment with pesticides of a slope prepared for dry rigid fastening should be carried out after the layout provided for by the project.

Treatment of slopes with herbicides of continuous action must be carried out no earlier than 10 days before laying the anchorage, preventing the herbicides from being washed off by rainfall.

4.5. Compaction of the base for rigid fastening to the required density should be carried out after planning and etching with pesticides.

4.6. At negative air temperatures, the installation of the filter or preparation for rigid fastening of the slope should be carried out from non-frozen, non-cohesive soils, while the following conditions must be observed:

a) frozen clods of 5 cm or more should be crushed or removed; in the layers, evenly distributed clods less than 5 cm in size, not more than 10% of the total volume, are allowed;

b) each layer should be laid immediately for its entire thickness;

c) before laying layers, snow and ice must be removed from the base;

d) during snowfall and blizzards, work on the installation of a return filter should be stopped. Before resuming work, it is necessary to remove snow and frozen clods of soil from the slope.

4.7. The device of stops that protect the clothing of the slope from slipping should be carried out before it is strengthened.

4.8. Laying of crushed stone and crushed stone on steep slopes should be done by pavers and planners. It is allowed to carry out planning by a bulldozer on slopes not steeper than indicated in his passport.

4.9. The use of stone paving for strengthening slopes and banks is allowed with an appropriate feasibility study. Stone fastenings of the banks under water are arranged in the form of a stone sketch with a natural slope from 1:1.25 to 1:1.5.

4.10. The layout of the rockfill to give the slope the required profile should be made after its settlement.

4.11. The device of monolithic concrete and reinforced concrete facing of slopes with a laying steeper than 1: 1 is carried out through the strip (in two stages) using formwork installed on concrete beacons.

4.12. The device of fastenings from monolithic concrete and reinforced concrete on earthen slopes with a laying of 1: 2.5 and more gently sloping should be carried out in accordance with the requirements of clause 7.11.

4.13. When strengthening the slope with monolithic reinforced concrete slabs, the following requirements must be controlled:

a) deviations from the thickness of the plates established by the project are allowed in the range from + 8 to - 5 mm;

b) there should be no cracks in the plates;

c) there should be no gaps between the material for filling the joints and the vertical edges of the plates.

4.14. Prefabricated reinforced concrete slabs should be laid on a reinforced slope from the base to the crest of the structure. The value of the protrusions between adjacent plates should not exceed 10 mm.

4.15. When laying prefabricated reinforced concrete slabs in winter, the planned surface of the return filter must first be cleared of snow and ice. Mounting plates must be evenly attached to the filter surface.

4.16. A monolithic asphalt concrete pavement is carried out by grippers using asphalt pavers on a dry, frost-free base at an air temperature of at least 5 ° C. With a coating thickness of up to 10 cm, the asphalt concrete mixture can be laid in one layer, and if the design provides for reinforcement of the coating, the reinforcing cage is laid on a slope before the mixture is laid and, during the laying process, is moved to the middle of the laid layer of the asphalt concrete mixture until it is compacted. With a coating thickness of more than 10 cm, the asphalt concrete mixture is laid in layers with individual layers rolling to the design density. If the project provides for reinforcement of the coating, then the frames are laid between the layers of the coating.

Deviations from the thickness of the asphalt concrete pavement established by the project should not exceed 10%. The laying of the asphalt concrete mixture into the grip should be carried out at a temperature of the mixture from 140 to 120°C. Laying a mixture with a temperature below 100 ° C is prohibited.

4.17. The asphalt mixture should be compacted with a smooth roller or a vibratory roller. Rolling should be carried out until the roller no longer leaves marks on the surface of the pavement, and the density of the asphalt concrete reaches the design one.

4.18. The construction laboratory checks the compliance of the physical and mechanical properties of asphalt concrete and the thickness of its layer with the requirements of the project, for which cores or cuttings of cooled asphalt concrete should be taken at the rate of one core or one cutting per 450 sq.m of pavement. Taking cores or clearings in the area of ​​the water's edge and fluctuations in water levels is prohibited. Holes from cores and cuttings should be immediately sealed with poured asphalt mortar.

4.19. Fastening of underwater slopes with a laying of 1:2.5 and more gentle from reinforced concrete and asphalt concrete slabs should be carried out using floating cranes across the slope from the bottom up in the direction against the river flow.

5. DRILLING AND EXPLOSION

5.1. The rules of this section apply to drilling and blasting during the development of tie-ins, pits, cleaning of rocky foundations and slopes for the construction of river hydraulic structures.

In the course of drilling and blasting operations, the requirements of SNiP III-8-76, the Uniform Safety Rules for Explosive Operations and the Uniform Safety Rules for the Development of Mineral Deposits by Open Mining, approved by the USSR Gosgortekhnadzor, as well as the requirements of this section, must be observed.

Drilling and blasting in deep canyons must be carried out in accordance with the Safety Instructions for Open Mining at Hydraulic Construction Facilities in Deep Canyons and Mountainous Areas, approved by the USSR Ministry of Energy and agreed with the USSR Gosgortekhnadzor.

5.2. When performing drilling and blasting operations, special requirements for the safety of rock foundations and slopes of structures under construction should be taken into account, depending on belonging to a certain group:

Group I - structures, in the base and slopes of which an increase in natural and the formation of additional cracks is allowed (discharge channels of hydroelectric power stations, spillways, clearing the channel in the downstream, platforms of open switchgears, approach channels of shipping locks in the downstream);

Group II - structures, the foundations and slopes of which require protective measures against the increase in fracturing during blasting (pits of concrete spillway and blind dams, supply channels to near-dam HPPs, trenches for a tooth of earthen and embankment dams, excavations of near-dam buildings of HPPs, approach channels in the upper pool , pits of navigable locks).

The assignment of structures to groups I and II should be made in the POS.

5.3. Drilling and blasting operations at Group I facilities are carried out without special protective measures.

5.4. For objects of group II, technical specifications for drilling and blasting operations should be drawn up, which indicate the method of development, the allowable amount of searches and shortages of soil, seismic safety restrictions for protected objects, the need for seismic control of explosions, blasting conditions near freshly laid concrete and other technological factors that ensure high-quality and safe work.

5.5. The development of rocks at objects of group II should be carried out in ledges, leaving a protective layer between the bottom of the blast holes of the lower ledge and the design contour of the pit in order to protect the base and pair it with the slopes from cracking during the explosion.

5.6. In areas located directly above the protective layer, loosening of the soil should be carried out with borehole charges. At the same time, re-drilling of wells into the protective layer is not allowed, and the size of the well grid is reduced to 70% of the grid size used in development without a protective layer.

5.7. The thickness of the protective layer is determined by the calculation in the POS according to the formula

				The power of the protective layer;
					The power of the zone of violations of the soil massif by the explosion;
					Permissible value of soil searches along the base.

The power of the disturbance zone h is within the range of up to 15 diameters of borehole charges exploded on a ledge directly above the protective layer, and should be specified by calculation in the drilling and blasting project, depending on the properties of the rock mass.

5.8. Permissible values ​​of overshoots and undershoots of soil should be specified in the technical specifications for drilling and blasting, depending on the design features of the structures.

5.9. Loosening of the soil of the protective layer is carried out by the explosion of charges on the overlying ledge. The protective layer is developed using rock-cleaning machines (excavators equipped with a backhoe, bulldozers with rippers) after cleaning the soil on the overlying ledge.

When planning the base for prefabricated reinforced concrete structures, it is allowed to loosen the protective layer with explosive charges according to Table. 3.

Table 3

Estimated capacity of the soil mass disturbance zone in charge diameters
Permissible maximum diameter of charges, mm

At the same time, re-drilling of wells and boreholes outside the protective layer is not allowed.

5.10. When conducting blasting at the slopes of pits at objects of group II, it is necessary to use contour blasting. For group I objects, the expediency of contour blasting should be established in the POS and specified in the drilling and blasting project.

5.11. The contour blasting parameters (distance between the charges, their mass and design) are determined by the calculation in the drilling and blasting project and are specified based on the results of experimental explosions. The use of bottom charges at the bases of structures of group II during contour blasting is not allowed.

The sequence of blasting contour charges and loosening charges is established by the drilling and blasting project.

5.12. Under unfavorable geological conditions, to ensure the safety of the rocky surface behind the contour plane and to protect slopes from weathering during prolonged exposure to atmospheric phenomena, a protective layer is left during contour blasting by placing the plane of contour charges in front of the design contour of the slope.

5.13. Cleaning and treatment of slopes after contour blasting should be carried out without the use of explosions.

5.14. The development of a protective layer after contour blasting to prepare the surface for concrete placement should be carried out in small areas without the use of explosions. The size of the prepared areas for concrete is established by the project for the production of concrete work.

5.15. If it is necessary to carry out blasting operations near freshly laid (up to 15 days old) concrete, as well as protected ground and underground structures and equipment, the permissible blasting parameters (ledge height, diameter and mass of charges, deceleration scheme and intervals) are established by calculation in the drilling and blasting project.

The values ​​of permissible vibration velocities for protected objects and equipment must be established in the technical specifications for drilling and blasting. Permissible vibration velocities for process equipment must be agreed with manufacturers.

The need for continuous or periodic seismic control during explosions is established by the technical specifications for the performance of drilling and blasting operations.

5.16. Underwater loosening of rocky soils is carried out in accordance with the requirements of Sec. 3 SNiP III-45-76.

6. UNDERGROUND CHAMBER WORKINGS

6.1. When performing work on underground chambers of river hydraulic structures (engine rooms of hydroelectric power plants, pumped storage and nuclear power plants, turbine conduits, gates, transformers, surge tanks, pumping, underground pools, installation chambers), the requirements of SNiP III-44-77, SNiP III- 15-76 and this section.

6.2. Depending on the requirements for the safety of the rocks surrounding the workings, drilling and blasting operations should be carried out when driving chambers:

in the sole, walls and roof of which a slight increase in natural cracks and the formation of artificial cracks are allowed, - borehole and blast-hole charges;

in the sole, walls and roof of which the increase in natural and the formation of artificial cracks is not allowed - by borehole and blast-hole charges contour blasting along the roof and walls and leaving a protective layer of rocky soil (rock) * along the sole, the size and method of development of which are determined by the PPR.

* Classification of rocky soils (rocks) is determined according to GOST 25100-82.

The values ​​of overruns for the design contour when driving chamber workings should not exceed, mm, with a group of rocky soil:

IV, V ......... 100

VI, VII ........ 150

VIII-XI ....... 200

Lack of rock, causing a decrease in the thickness of the supporting structures, is not allowed.

6.3. The penetration of chambers left completely or partially without lining should be carried out by contour blasting to ensure the preservation of the natural state of the surrounding rocky soils.

6.4. As construction approaches to chamber workings, workings of permanent structures should be used: outlet, inlet and transport tunnels, tire-cargo, assembly and ventilation shafts. With an appropriate feasibility study, additional approaches are allowed.

6.5. The construction of chambers with a height of more than 10 m, in which the design provides for a permanent lining, must be carried out in the following order: sinking the under-roof part of the excavation and fixing the vault, followed by development of the main rock mass (core) of the chamber and erection of the wall lining.

6.6. Sinking of the under-roof part of chamber workings with a span of up to 20 m in strong medium-fractured rocky soils should be carried out, as a rule, for a full section, followed by the erection of a permanent lining of the arch.

The sinking of the under-roof part of chamber workings with a span of more than 20 m in strong medium-fractured rocky soils and, regardless of the span in medium-strength rocky soils, should be carried out, as a rule, by a stepped method, ahead of the central part of the section, or with the driving of an advanced working for the entire length of the chamber. The need and possibility of developing the under-roof part of chamber workings in strong medium-fractured rocky soils for a full section with a span of more than 20 m should be justified in the PPR.

The penetration of the under-roof part in low-strength soils, regardless of the span of the chamber working, should be carried out, as a rule, by the method of supported arch. The expediency of driving with preliminary fixing of an array of weakly stable rocks must be justified by a technical and economic calculation. Methods of pre-fixing the massif (cementing, chemical fixing, installation of prestressed and conventional anchors from auxiliary workings) are established by the POS depending on the engineering and geological conditions.

6.7. The development of the core of chamber workings, in which the design provides for a permanent lining device, should be carried out from top to bottom with ledges with a height, m:

in strong medium-fractured rocky soils - up to 10;

in rocky soils of medium strength - up to 5;

in low-strength soils - up to 3.

At the same time, in weakly stable rocks, the development of ledges should be carried out with the abandonment of rock pillars (to support the overlying sections of the arch or walls) and their subsequent development and concreting of the walls in a checkerboard pattern or driving sections of trenches along the walls to the height of the developed ledge and concreting the walls in the first place.

When developing chamber workings, systematic and careful monitoring of the stability of the walls should be carried out. In the event of a danger of wall movements inside the chamber, the nature of possible movements in time should be identified and, if necessary, measures should be taken to strengthen the wall support by installing spacer beams or anchors.

The height of the ledges, the dimensions of the pillars of the rock and sections of the chamber, measures to reduce the effect of wall deformation on the stress state of the structures, the material of the spacer beams, the length of the anchors are assigned by the PPR depending on the specific engineering and geological conditions of construction.

6.8. The development of chamber workings in permafrost rocks should be carried out in accordance with the requirements of paragraphs. 6.5-6.7, carrying out daily monitoring of changes in the temperature regime of workings, rock stability and thawing halo. The temperature regime during the construction of chambers in permafrost rocks and measures to maintain it are established by the POS.

6.9. The type of temporary fastening of chamber workings during their development is determined in the PPR, while:

in strong medium-fractured rocky soils, temporary fastening, as a rule, is not carried out, but in order to avoid possible delamination and fallout of rocky soil in certain fractured sections of the arch and walls (fractured sections are determined during the rocky ground after blasting), a metal mesh should be installed along the anchors;

in rocky soils of medium strength, fastening should be done with anchors and sprayed concrete;

in low-strength soils, the vault and walls should be fixed with metal mesh anchors and sprayed concrete; the time before the erection of a permanent lining of the chamber should be minimal and justified by the PPR.

The use of arch support as a temporary support is allowed in exceptional cases for the support of individual workings (phases of work) with a proper feasibility study.

6.10. The installation of temporary support in the development of chamber workings in permafrost rocky soils should be carried out after the development of the face. The type of temporary support is determined by the POS. The development of chamber workings in permafrost rocky soils without temporary support is allowed only in soils whose stability does not decrease during thawing.

6.11. In the projects for the production of concrete work for the construction of permanent linings of chamber workings, measures should be taken to ensure dense filling of the interlocking part of the vaults with concrete mixture, as well as the solidity of the joints of the walls with the heels of the vaults.

7. CONCRETE WORKS DURING THE CONSTRUCTION OF MONOLITHIC

AND ASSEMBLY-MONOLITHIC STRUCTURES

7.1. In the production and quality control of formwork, reinforcement and concrete work, as well as work on the preparation and transportation of concrete mix, installation of precast concrete structures, the requirements of SNiP III-15-76, SNiP III-16-80 and this section should be met.

7.2. For the preparation, transportation, laying, care and quality control of concrete during the construction of river hydraulic structures, technical specifications must be drawn up, approved in the prescribed manner.

7.3. In the process of preparing, transporting and laying the concrete mix, in order to ensure the required characteristics of concrete of river hydraulic structures, along with the requirements of the relevant sections of SNiP III-15-76, it is necessary:

ensuring, as a rule, no more than two overloads in the process of transporting and supplying the concrete mix to the concreting blocks;

use of powerful vibrators or vibrator packs to compact the concrete mix during placement;

the use of machines specially equipped with mechanical brushes for removing the cement film from the horizontal surfaces of blocks of concrete lightly reinforced structures.

7.4. Road and rail bulk transportation of concrete mix for concreting river hydraulic structures, as a rule, should be carried out in specially equipped concrete dump trucks. The capacity of vehicles for transporting the concrete mixture must correspond to the capacity of the buckets, with the help of which the concrete mixture is supplied to the concreting blocks.

Concrete mixture should be transported over a distance of more than 15 km in concrete mixer trucks. Transportation of a concrete mixture over a distance of more than 15 km in concrete dump trucks is allowed provided that additives are used in the concrete mixture - setting retarders.

7.5. The bases and surfaces of construction joints prepared for laying the concrete mix, along with the instructions of SNiP III-15-76, must meet the following requirements:

the base must be cleared of debris, dirt, snow, ice;

surfaces of concrete bases of horizontal and inclined construction joints, in addition, must be cleaned of cement film. The removal of the cement film should be carried out, as a rule, mechanized;

the surfaces of horizontal and inclined construction joints in reinforced concrete structures and vertical construction joints in concrete and reinforced concrete structures should be cleaned from the cement film if there are appropriate requirements in the project.

7.6. In order to prevent the formation of cracks from temperature effects during the hardening of concrete, the erection of the structure should be carried out, as a rule, evenly along the entire front with interruptions in the laying of blocks adjacent in height in the range from 3 to 10 days. In the event of an increase in breaks, additional project requirements for the temperature regime of block hardening should be met.

7.7. The period of overlapping of individual layers or grips in the process of concreting blocks should not exceed 3 hours, depending on the type and properties of cement, as well as the temperature conditions of concrete placement. In the case of using additives in the concrete mix - setting retarders, the overlapping period can be increased. In each case, the period of overlap must be specified by the construction laboratory.

7.8. Depending on the possible intensity of concreting, the dimensions of the blocks in the plan and the allowable periods for overlapping layers or grips, the laying of the concrete mixture into blocks can be carried out using:

layered technology, when concreting is carried out in several layers over the entire block area;

step technology with the number of steps no more than three - when compacting the concrete mixture with manual deep vibrators and no more than two - when using means of intra-block mechanization of work;

Toktogul (single-layer) technology, which involves concreting blocks up to 1.5 m high at once in one layer.

Steps during concreting using stepped technology should be carried out parallel to the longitudinal axis of the structures. The direction of concreting is from the downstream to the upstream. The step width should be at least: 2 m - when compacting the concrete mixture with manual vibrators and 3 m - when using mechanized means.

The height of the blocks during concreting using the Toktogul technology should be from 0.5 to 1.5 m; concreting should be carried out under the protection of the tent; riding on previously laid concrete can be carried out after it reaches a strength of at least 5 MPa (50 kgf / sq. cm); all work must be carried out mechanically; the means of intra-block mechanization in terms of their technical capabilities must correspond to the accepted height of the blocks.

7.9. Compaction of concrete in blocks of concrete lightly reinforced structures (with saturation with reinforcement up to 15-20 kg per 1 cubic meter) should be carried out with the maximum use of single crane vibrators or vibrator packs suspended on mechanisms for intra-block operations (small-sized electric tractors, manipulators, etc. .), while the mobility of the concrete mixture, measured by the draft of a normal cone, should not exceed 2 cm.

The distance between the individual vibrators in a package must not exceed 1.5 times the vibrator range. The vibrators in the package should, if possible, be installed with an inclination of up to 30° from the vertical, parallel to each other in order to improve the study of the contact zone between the individual layers of the concrete mixture. The height of the laid concrete layer should not exceed the length of the working part of the used vibrators.

7.10. For heavily reinforced reinforced concrete structures, where compaction of the concrete mixture is difficult, it is allowed to use concrete mixtures of increased plasticity, compacted by vibrators, and in cases where the location of the reinforcement prevents the use of vibrators, it is allowed, in agreement with the design organization, to use cast concrete mixtures with a normal cone draft from 22 to 24 see without vibration compaction.

7.11. When concreting the fastening of the slopes of earthworks (dams, dams), mechanized methods of supplying and laying the concrete mixture (concrete-laying mechanisms and complexes) or bulldozer technology should be used. When using bulldozer technology, the distribution of the concrete mixture along the slope during concreting is carried out by a bulldozer, the compaction of the concrete mixture is carried out by a vibrating plate mounted on a tractor. The bulldozer must move the concrete mixture in the direction from the base of the slope to the ridge, moving along the layer of concrete mixture (without going to the reinforced structures not covered with concrete mixture), the distance of movement of the mixture should not exceed 20-25 m. Bulldozer technology can be used with the thickness of the fastening not more than 20 cm. The speed of movement of the tractor with a mounted vibrating plate in the process of compacting the concrete mixture should not exceed 1 - 2 m / min. The mobility of the laid concrete mixture when using bulldozer technology, measured by the normal cone draft, should not exceed 2 cm. When compacting the concrete mixture with a vibrating plate mounted on a tractor, it is possible to use fine-grained (sandy) concrete in the fastening structure.

7.12. To ensure the temperature regime of concrete hardening in massive concrete structures of the STP, the following measures should be provided:

regulation of the temperature of the concrete mixture in the process of its preparation;

pipe and surface cooling of laid concrete; arrangement of tents or greenhouses above the block and maintenance of an artificial climate in them;

arrangement of warm formwork on the outer surfaces of the blocks;

insulation or shelter of horizontal surfaces of blocks.

The regulation of the temperature regime of concrete in a massive structure should be regulated by the technical specifications.

7.13. Cooling of concrete in massive concrete structures is carried out in two stages: the first stage - in the process of laying and hardening concrete to reduce the temperature of exothermic heating in the block (duration 2-3 weeks); the second stage is the cooling of the concrete in the structure to the average annual temperature of the outside air, which makes it possible to monolithize the seams of the structure.

7.14. To control the temperature of the concrete at the first stage, surface or pipe cooling should be used, using, as a rule, river or ground water of natural temperature.

Surface cooling of concrete should be used for blocks with a height of 0.5 to 1 m by irrigation, which provides a layer of water on the surface of the cooled concrete, which has a constant organized flow in one direction at a speed of 5-8 cm / s.

The cooling rate at the first stage, when using both surface and pipe cooling, should not exceed 1°C per day during the first 8-10 days. after laying the concrete mix and 0.5°C per day thereafter.

7.15. At the second stage, as a rule, pipe cooling is used. The temperature of the water used for cooling at the second stage should be 2-3°C lower than the temperature of the concrete, at which it is envisaged to monolithic the joints of the structure. In the absence of natural sources of water with the specified temperature, an installation for artificial cooling of water should be provided.

The rate of concrete cooling at the second stage should not exceed 0.4-0.5°C per day. In this case, concrete cooling should be carried out in tiers with a height, as a rule, of at least 10 m.

7.16. When selecting concrete compositions to reduce the temperature of exothermic heating in weakly reinforced structures with saturation with reinforcement up to 20 kg per 1 cubic meter, it is necessary to provide for the use of medium-thermal cements and the maximum reduction in their consumption. The reduction in cement consumption should be achieved by using aggregates of a multi-fractional composition, low-slump concrete mixtures with a normal cone draft of up to 2 cm, the addition of fly ash, as well as the use of pozzolanic and slag Portland cement for the internal and underwater zones of the structure.

7.17. In winter, the temperature difference between the surface and the center (core) of the concrete mass should not exceed 25°C. Blocks concreted in winter must be kept in insulated formwork until the core of the block reaches a temperature exceeding the outside air temperature by no more than 25°C.

The stripping of the side faces before concreting adjacent blocks should be carried out under the protection of a tent or a greenhouse. The surface of blocks concreted in the warm season and not cooled down before the onset of the cold period (minimum daily temperature 0°C, average daily temperature 5°C and below) must be insulated.

In dams with expanded seams and buttress dams built in harsh climatic conditions, it is necessary to close the seams and sinuses for the winter period and provide them with heating.

7.18. As the main type of formwork for concrete low-reinforced structures (gravitational, arch, arch-gravity, buttress dams), cantilever metal or wood-metal formwork should be used; When developing formwork, the requirements of GOST 23478-79 should be followed.

Metal formwork structures must be factory-made.

The use of stationary and standard non-reversible formwork is allowed for formwork of faces with reinforcement protrusions, concreting of embedded parts, cutting to a rocky base, as well as for surfaces that have a complex geometric shape, double curvature, in particular, structures of the flowing part of the HPP building.

For the surfaces of vertical and inclined construction joints, if it is possible to use the structures of the working reinforcement as a supporting frame, a mesh metal fixed formwork should be used.

For surfaces of blocks to be kept in formwork for a long period (over 15 days), insulated formwork with a heat shield remaining on the concrete surface after stripping should be used.

7.19. The methods, terms, schemes and technological sequence of work on the manufacture, transportation, installation and monolithic precast concrete elements of a hydraulic structure should be regulated by the PPR and special technical conditions.

7.20. Quality control of the concrete mixture should be carried out by a construction laboratory in accordance with GOST 10181.0-81 - GOST 10181.4-81. Control samples should be taken at least once per shift at the concrete plant and at least once a day at the place of laying for each brand of concrete, as well as every time the quality of the raw materials changes.

7.21. The control of the strength of concrete of monolithic and prefabricated concrete and reinforced concrete structures should be carried out in accordance with GOST 18105.0-80 - GOST 18105.2-80 by a statistical method, which makes it possible to achieve constancy of the provision of normative resistances of concrete adopted in the calculation of structures.

In the manufacture of single structures of small volume, when it is not possible to obtain the number of results necessary for calculating statistical characteristics, as an exception, it is allowed to use a non-statistical method for monitoring the strength of concrete, subject to GOST 18105.0-80, GOST 18105.2-80.

Simultaneously with the strength control on the same samples, the density control of concrete should be carried out in accordance with GOST 12730.0-78 and GOST 12730.1-78.

Concrete water resistance control must be carried out in accordance with GOST 12730.0-78 and GOST 12730.5-78, frost resistance control - in accordance with GOST 10060-76.

The number of control samples for testing concrete for water resistance and frost resistance should be established according to Table. 4.

Table 4

The total volume of concrete in the structure, thousand cubic meters	The volume of concrete mixture, cubic meters, from which one sample for testing
	water resistance		frost resistance
	in massive concrete structures	in reinforced concrete structures	in massive concrete structures	in reinforced concrete structures

8. INSTALLATION WORKS

8.1. When installing technological equipment of river hydraulic structures, the requirements of SNiP 3.05.05-85, SNiP III-18-75 and this section should be met.

8.2. Prior to the start of installation work, the bases of installation organizations provided for in the PIC, as well as installation sites of the operational period, must be prepared for receiving equipment.

8.3. Installation of operational cranes should be carried out, as a rule, on permanent crane tracks. In the case of installation of operational cranes on temporary crane tracks, the latter should not exceed the draft established by the Rules for the Construction and Safe Operation of Cranes approved by the USSR Gosgortekhnadzor.

8.4. In the case of a non-push method of mounting embedded parts of mechanical and hydraulic power equipment, the base for installing embedded parts must be made in accordance with the PPR or the installation instructions of the equipment supplier.

8.5. During installation work, it is necessary to prevent clogging of the grooves or the shutters and gratings installed in them.

8.6. The assembly of individual units and the installation of the working mechanisms of hydraulic turbines and hydro generators must be carried out in an area protected from atmospheric precipitation and protected from possible ingress of construction debris.

8.7. Installation of the control system, installation and soldering of the stator windings, soldering of interpole connections of the generator rotor, installation of the cooling system for the conductive parts of the generator, thrust bearing and bearings, as well as start-up, adjustment and testing of the mounted hydraulic unit must be carried out at a positive temperature of at least 5 ° C.

9. SOIL CEMENTATION

9.1. When performing grouting work, the requirements of SNiP 3.02.01-83 and this section should be met.

9.2. When combining grouting and general construction work, the construction schedule should provide a front for grouting work, taking into account compliance with the requirements of the grouting process provided for by these standards and the work project.

9.3. Cementing work in the zone of influence of backwater, as a rule, should be carried out before the reservoir is filled. If it is necessary to carry out grouting work under conditions of partial or full pressure on the PPR structures, changes in the conditions for performing work caused by a rise in pressure should be taken into account.

9.4. Cementing work at the base of the hydraulic structure must be completed before drainage is installed.

9.5. Cementing work, as a rule, should be carried out under load (thickness of the overlying soil, artificial embankment, body of a concrete structure, special concrete slab). Cementing work should be started after work has been completed to ensure the design thickness of the surcharge and its impermeability to cement mortar. When carrying out cementation work under a load of freshly laid concrete, work is allowed to begin 10 days after the completion of the concrete mix.

9.6. After completion of the cementation of all zones and carrying out the total cementation of the well, if it was provided for by the project, the wellbore must be plugged with a solution.

9.7. When carrying out grouting works at an average daily outdoor temperature below 5°C, the following requirements must be observed:

cemented soils within the zone of distribution of the cement mortar must have a temperature of at least 2 ° C;

the temperature of the solution injected into the well should not be below 5°C;

temperature measurements of the injected solution, outdoor air and indoors should be recorded in the work log.

9.8. In case of impervious purpose of soil cementation, the control of the work performed should be carried out by drilling, hydraulic testing and cementing of control wells, determined by the project.

9.9. The volume of control wells should be, as a rule, 5-10% of the volume of production wells.

9.10. Cementing work in the section of the impervious curtain should be considered sufficient if the specific water absorption in the control wells, in terms of its average value and permissible deviations from the average value, meets the requirements of the project or the achievable values ​​of specific water absorption for the soils of the tested area.

9.11. The method of monitoring the work performed on strengthening cementation should be established by the project and consist of hydraulic testing and cementation of control wells or from determining the deformation properties of soils by geophysical methods. It is allowed to use these methods simultaneously.

10. TRANSFER OF THE RIVER DURING THE CONSTRUCTION PERIOD

AND CONSTRUCTION OF JUMPERS

10.1. The scheme for skipping the flow of the river during the construction period should be decided in the POS, taking into account the layout of the main structures, the sequence and sequence of their construction, as well as taking into account topographic, geological and hydrological conditions and in compliance with the requirements of navigation and timber rafting.

10.2. The construction of bridges should be carried out during the period between floods, timing the work on their construction to the timing of the passage of the minimum flow of the river.

When erecting bridges in winter from ice, sufficient bearing capacity of the ice cover for vehicular traffic must be ensured. The lane must be completely cleared of ice prior to commencement of work on the construction of lintels.

10.3. When preparing the base of all types of jumpers above the water's edge, the requirements of SNiP 3.02.01-83 should be followed.

The foundation in the river bed for cofferdams made of soil materials is subject to inspection and, as a rule, does not require preparation. In case of occurrence of stone screes and boulders at the base, the latter must be removed.

The foundation in the river bed for ribbed and cellular cofferdams is prepared by removing individual large stones and boulders and, if necessary, leveled by adding crushed stone or gravel-sand materials.

10.4. Lintels from soil materials should be erected, as a rule, from soils of useful excavations (pits, channels, etc.). Lintels that are part of the main structures must be made of materials and according to specifications in accordance with the requirements of the design of these structures.

10.5. Ridge jumpers should be erected, as a rule, from a two-edged beam. With a row height of up to 6 m, it is allowed to use timber of any species, with a height of more than 6 m, only coniferous timber should be used. Connections in ribbed lintels should be made on metal dowels.

10.6. The assembly of robes is carried out on the shore on stocks according to the specified dimensions. The finished rows are launched into the water, towed to the place of installation and anchored in the alignment of the cofferdam, after which they are loaded with stone or soil and installed on the bottom.

In winter, it is allowed to assemble the rows on ice if the ice has sufficient bearing capacity.

With a rocky base, detailed measurements of the bottom should be made, on the basis of which the lower crowns of the rows are cut according to the bottom configuration.

10.7. Before installing a lintel of a cellular structure from a metal sheet pile, in order to determine the driving conditions, it is necessary to perform a test driving of the sheet pile to the design depth, followed by pulling it out. The filling of the cylindrical cells of the jumper must be carried out to the full height, and the filling of the segment cells should be carried out evenly, not allowing the level in neighboring cells to exceed by more than 2 m.

10.8. Prior to pumping out the pit, the lintels must be examined by the customer, designer, contractor, and an act must be drawn up on the readiness of the lintels to accept pressure.

10.9. The state of the jumpers must be permanently monitored. For timely repair and restoration of damaged parts of the jumpers during the period of pumping out the pit and floods, an emergency supply of materials should be prepared in the required amount.

10.10. The decrease in the water level when pumping out the pit should not exceed 0.5 m per day. In case of detection of soil removal, it is necessary to carry out strengthening work in the area of ​​removal.

11. CLOSURE OF RIVER COURSES

11.1. The scheme for blocking the riverbed should be decided in the SDP, taking into account hydrological and geological conditions, a drop at a banquet, the flow rate and speed of the water flow, the throughput of the drainage tract, the size of the material for blocking, transport conditions, the carrying capacity of vehicles and loading facilities.

11.2. The order of work and the timing of blocking the channel on navigable and timber rafting rivers must be agreed with the organizations of the river fleet and timber rafting. In addition, if there are regulating reservoirs in the upstream, the procedure for shutting off works should also be agreed with the operation service of these reservoirs.

11.3. The blocking of the riverbed should be timed to coincide with interflood periods with minimal water flow in the river, and on navigable and timber-rafting rivers - at the end of navigation or a non-navigable period.

11.4. The channel closure parameters (drop at the banquet, flow velocity in the hole, size and volume of material for closure) at the design stage should be calculated for the maximum water flow in the river in the month of closure with a probability of exceeding 20%.

If there is a regulating reservoir on the river upstream of the blocking point, the calculated water flow during blocking should be taken as a special reduced discharge agreed with the reservoir operation service.

Immediately before blocking the channel, the blocking parameters should be specified taking into account the actual water flow in the river, taken on the basis of a short-term forecast for the blocking period.

11.5. Prior to the commencement of work on blocking the riverbed, the following preparatory work, provided for by the PDS, must be completed:

create warehouses of materials necessary for blocking the channel, placing them as close as possible to the place of blocking on non-flood marks and organize entrances to them;

to prepare a spillway for switching the flow of the river to it;

before the flooding of the foundation pit of concrete structures, to which the costs are switched, to carry out a preliminary dismantling of the enclosing lintels to the minimum possible size according to the conditions for skipping costs before blocking the channel;

carry out a preliminary restriction of the riverbed to a minimum size, taking into account the conditions of navigation.

12. PROTECTION OF THE ENVIRONMENT

12.1. Prior to filling the reservoir, in accordance with the project, rare and endangered species of flora and fauna must be collected and removed from its zone and the necessary conditions for their development and reproduction must be created, measures for scientific research, engineering protection or transfer of historical and cultural monuments must be carried out.

12.2. Before the river bed is closed, fish passage facilities should be built, and before the reservoir is filled, spawning and rearing farms and fish hatcheries should be built.

12.3. Quarries of soil materials for backfilling of earthworks should, as a rule, be placed in the flood zone.

12.4. When performing work, it is necessary to provide and strictly implement measures to ensure compliance with applicable laws in the field of environmental protection.

The text of the document is verified by:

official publication

Gosstroy of the USSR - M.: CITP, 1985

5.14. Loesslike, sandy-gravelly-pebbly and moraine soils are allowed to be laid in layers with compaction by mechanical means (rolling, tamping, etc.), as well as by layer-by-layer filling into water - into ponds specially arranged during the construction of the structure, and into natural reservoirs, without the construction of jumpers and the organization of drainage. At the same time, the preparation of the bottom of a natural reservoir is determined by the project for the production of works and the requirements of SNiP 2.06.05-84. Dumping of soil into a natural reservoir without the installation of jumpers is allowed only in the absence of velocities capable of eroding and carrying away small fractions of the soil.

The erection of structures by the method of dumping soil into water into artificial ponds should be carried out by separate maps, the dimensions and volumes of which are determined by the productivity of the equipment and the established intensity of dumping the soil. The boundaries of the maps of the laid layer, fixed by embankment dams, must be shifted relative to the boundaries of the previously laid layer by a distance set by the thickness of the layers being poured. It should be at least two times the width of the embankment dams.

The thickness of the layers when filling the soil into the water is established by the project or technical conditions, depending on the nature of the soil, the intensity of its filling, the carrying capacity of transport vehicles, the type and size of the structure.

When assigning the height of the backfill layer depending on the granulometric composition of the soil, it is recommended to use the graph (Fig. 3), built according to table 13.

Rice. 3. Curves of granulometric compositions of soils used in the construction of various types of structures

Curves I-II limit the area of ​​soils recommended for laying in ponura, screens and cores with layers of no more than 2 m; curves II-III limit the area of ​​soils recommended for laying in screens, cores and homogeneous dams with layers of 2-4 m;

1 - earthen dam Niva HPP-1; 2 - earthen dam of Knyazhegubskaya HPP; 3 - Upper Tuloma dam; 4 - Vilyuyskaya dam; 5 - the core of the dam of the Irkutsk hydroelectric power station; 6 - downcast and screen of the Iriklinskaya dam; 7 - the core of the dam of the Serebryanskaya HPP-1; 8 - Khantai dam;

9 - declining dam of the Volgograd hydroelectric power station; 10 - earthen dam Khishrau HPP; 11 - bridge of the Nurek dam; 12 - earthen dam Bolgar-Chay; 13 - jumper screen and experimental site of the Cheboksary dam; 14 - the screen of the dam of the Perepadnaya hydroelectric power station.
The approximate values ​​of the height of the backfill layer are as follows: when erecting structures from sandy-gravel soils, the height of the backfill layer should be taken from 4 to 10 m, for sands and sandy loams - up to 4 m. When building structures from loam, the height of the backfill layer should not exceed 2 m, for clay - no more than 1 m.

The suitability of a particular type of soil for its filling into water is determined by the project. Backfilling of soil into water must be carried out in compliance with special technical conditions (see "Guidelines for the construction of soil structures by the method of filling soil into water", P 22-74 / VNIIG, 1975).

5.15. A representative of the soil laboratory (field control post) should be present at the place where the soil was dumped into the maps. He monitors the quality of the brought soil, the uniformity of soil dumping along the front of the constructed map and the correct movement of vehicles on the laid soil.

5.16. Preparation of the base of the structure, installation of benchmarks, mapping, backfilling of the embankment dam, filling the ponds with water and other preparatory work are checked by a commission with the participation of representatives of design and construction organizations and the geotechnical control service and, as soon as they are ready, are accepted according to the acceptance certificate.

5.17. When dumping into the water, it is necessary to ensure uniform laying of the soil along the front of the constructed map, while achieving a constant water saturation of the laid soil. It is necessary to set such an intensity of backfilling soils into water, which eliminates the possibility of their waterlogging, free soaking and swelling, provides the specified soil moisture and a sufficiently high density after the completion of the process of soil compaction in the structure.

Backfilling should be carried out continuously until the map is completely filled with soil. In the event of a forced break with a stoppage of work for 4 hours or more, the water from the pond must be removed.

By the end of backfilling, a certain amount of liquefied soil is formed in each pit, therefore, before the completion of filling the pit, the level of the pond must be sharply reduced by unloading the soil from the last 15-20 dump trucks into liquefied soil.

Particular attention should be paid to: compliance with the design thickness of the backfill layer, uniform initial compaction of the soil by moving vehicles, maintaining the specified water depth in the pond and water saturation of the laid soil.

5.18. For the construction of structures by the method of filling soils into water, soils of any degree of clodiness are suitable, from homogeneous in a powdery state to large clods that are difficult to mechanically crush. In the mechanized development of dense clays slowly soaking in water, it is necessary to control the presence of at least 20-30% of soil with a clod size of no more than 10 cm, which will soak in water and serve as a material for monolithic larger clods.

The initial water saturation of the soil during backfilling is controlled by determining the degree of moisture, which should not be more than 0.75-0.85. To determine it, the density of the soil, humidity and density of dry soil are established from the samples taken.

5.19. The degree of moisture is determined by samples of the soil laid in each layer. Samples should be taken along the entire height of the laid layer and at least three samples along the depth of the pit.

5.20. Degree of humidity S r soil is determined by calculation by the formula:

S r = (W ·  d ·  s) / [( s -  d)  W ], (11)

where W- humidity;  d- density of dry soil (density in a dry state);  s- density of particles of the dumped soil.

5.21. If the density of the dry soil is 85% or more of the design density of the dry soil, then the initial compaction for the slopes should be considered satisfactory. For dams with a height of up to 25 m from homogeneous soil or with screens and cores, the initial soil compaction should be at least 90% of the design density of dry soil, and for high dams, the initial soil density must be determined empirically, and the requirements for the initial soil density must be increased .

5.22. In case of unsatisfactory indicators of the density of dry soil of the constructed map, additional compaction of the soil by loaded dump trucks should be carried out. In such cases, for subsequent maps, the thickness of the fill layer must be reduced so that the initial compaction meets the established requirements. A change in the thickness of the backfill layer should be made in agreement with the representative of the design organization.

5.23. In order to take soil samples, pits or wells are passed in the body of the embankment. One of the indirect indicators of high-quality soil filling is the stability of the vertical walls and the solidity of the soil throughout the entire depth of the pit.

The assessment of the quality of laying the soil in the structure is carried out on the basis of laboratory tests of samples taken in pits with cutting rings or in boreholes with a sampler.

When erecting structures from soils with impurities of pebbles and boulders, sampling is carried out using the "hole" method.

When erecting structures by dumping soil into water, it should be borne in mind that the final density of the soil in the body of the structure is reached over time as a result of the effect of the structure's own weight and the physicochemical processes occurring in soils poured into water. Therefore, quality control of work should be carried out not only in the process of filling the soil, but also 15 and 30 days after the construction of the map.

5.24. Soil samples taken 15 and 30 days after filling are tested in a soil laboratory - moisture content, soil density, dry soil density, porosity coefficient and degree of moisture are determined.

At the same time, the density of dry soil, equal on average to the design density of dry soil specified in clause 5.21, should be recognized as sufficient for a satisfactory assessment of the quality of work.

5.25. For a satisfactory assessment of the quality of construction of a structure, quantitative indicators should be on average not less than 95% of the corresponding indicators established by the project.

Upon receipt of indicators that constantly meet the requirements of this paragraph, sampling and their research after 15 and 30 days may be terminated.

If after 30 days the density specified in clause 5.21 is not achieved, the decision on further research and the possibility of changing the technical conditions regarding the appointment of a control value for the density of dry soil must be taken by the design organization and the customer.

The sealing of the pits should be carried out in layers of 30-40 cm moistened with soil with compaction to the design density.

All identified deficiencies, recommendations for their elimination, agreed changes in the technology of work, records of acceptance of finished maps and other instructions from the geotechnical control service should be entered in the field control log.
Alluvial structures
5.26. The geotechnical service controls the alluvium technology in terms of:

a) the correct laying of distribution slurry lines and the supply of slurry to the alluvium map in accordance with the project;

b) pulp distribution over the surface of the alluvium map;

c) embankment devices in accordance with the project and interface of adjacent sections of maps;

d) compliance with the intensity of alluvium adopted in the project (the rate of build-up of the alluvial soil in height per day) and the thickness of the layer of alluvial soil;

e) preventing the formation of scours in the reclaimed soil or stagnant zones where fines can be deposited within the side zones;

f) the state of the slopes of the structure and their formation according to the project;

g) compliance with the operating regime of spillways and clarification of waste water, as well as preventing the discharge of waste water with increased turbidity compared to the project into water bodies;

h) compliance with the width of the pond adopted in the project and technical conditions at various levels of alluvium;

i) fulfillment of the requirements of the project and SNiP 3.01.04-87 for the alluvium of structures during the performance of work.

Observations of the alluvial structure are carried out by the geotechnical service until the end of its construction. If the structure is not put into operation immediately after that, the geotechnical department of construction or the central geotechnical laboratory takes over the supervision until the acceptance of the structure into operation. Further observations are carried out by the personnel operating the hydroelectric complex.

5.27. When the embankment device is checked, its height, cross-sectional dimensions and its placement in the plan are checked in accordance with the location specified by the project. Before the beginning of the alluvium of the structure, the excess of the lowest mark of the embankment crest above the top of the water intake openings of the discharge structures and the compliance of this value with the one adopted in the project or established by calculations must be checked.

When arranging the embankment using a bulldozer inside the pit, it is necessary to pay attention to preventing the creation of depressions on the surface of the pit near the embankment, where, as a result of stagnant phenomena, small fractions can be deposited, and there may also be alluvial rollers (combs) between the penetrations of bulldozers, which prevent the correct distribution of the pulp along alluvium surface and lead to a decrease in the density of the alluvial soil.

When a bulldozer is building a dike from soil washed up behind the design slope contour from the outside of the structure, it is necessary to control the dimensions of the enumeration in relation to the design slope contour.

Note. All current geodetic works during the alluvium of structures and geotechnical control are carried out by the organization conducting the alluvium.
5.28. The correct distribution of the pulp on the alluvium map is fixed visually. During the construction of dams with a core, the pulp flows from the point of discharge from the slurry conduit to the edge of the pond should have a direction normal to the axis of the dam. Control over the position of distributing slurry lines can be carried out using rails that establish a straight pipe arrangement. To control the thickness of the alluvium layer according to the project during the pulp supply process, it is recommended to place T-shaped stakes along the distribution slurry line laying in 50-100 m, the bar of which corresponds to the height of the layer to be applied.

5.29. The control over the intensity of alluvium, the thickness of the actually reclaimed soil layers and the slope of the alluvium of the side zones is carried out according to the readings of the rails. The intensity is determined by dividing the average thickness of the layer washed over a certain period by the duration of the period in days or hours.

The slope of the alluvial slope is set along the rails located on the same diameter, and is determined by the formula:

i = [( 1 -  2) / l r] 100, (12)

where i- slope, %;  1 - absolute or conditional mark of the ground surface along the first rail, m;  2 - the same, on the second rail, m; l r- distance between rails, m.

Operational control over the condition of the slopes and the embankment device is carried out visually by fixed special signs (milestones), which are installed every 50-100 m and increase as the alluvium flows.

A control check of the magnitude of the slope in the process of alluvium of the structure is carried out based on the results of monthly geodetic measurements.

5.30. When reclamation of structures with a nuclear zone, the size of the pond and its position on the map within the specified boundaries should be monitored every shift using rails set on each diameter, or by special milestones that fix the design outline of the pond at a given fill mark. Their installation is carried out periodically as alluvium, after 2-3 m in height. The state of the pond is recorded in the log of alluvial works. In the event that its size or position does not correspond to the specified ones, the personnel conducting the alluvium is immediately notified in order to take appropriate measures.

5.31. The size of the settling pond within the core zone of an inhomogeneous dam determines the granulometric composition of the soil deposited in the pond and forming the core of the dam. In some cases, for example, when supplying soil, the composition of which does not correspond to the design, the width of the pond can be changed on the spot. These changes are determined by the requirements for the formation of a core with a given granulometric composition of the soil and the conditions for the discharge of fine fractions, the deposition of which in the core is not allowed. The decision to change the width of the pond is made by the chief construction engineer in agreement with the organizations designing the dam and the work, on the proposal of the head of the geotechnical service.

5.32. When inundating heterogeneous dams with a core, a sketch of the boundaries of the pond should be periodically made with the designation of existing spillways for the removal of clarified water, since the outline of the nuclear zone is determined from these sketches. Simultaneously with the sketch, the mark of the water level in the pond should be fixed.

Note. Compliance with the location of the water edge accepted in the project on the transverse profile of the dam is one of the main requirements for the quality of the alluvium of the structure. Emergency, even short-term (less than 2 hours) rises in the level of the pond lead to flooding of the alluvium slope within the intermediate and lateral zones and the formation of layers of silt-clay fractions due to the sedimentation of these fractions from the water of the settling pond. Continuous interlayers of silty-clay fractions in the body of the lateral zone from non-cohesive soil can, during the operation of the dam, cause the formation of perched water and seepage of seepage water on the downstream slope.

5.33. The control over the state of the flowing (technological) pond during the filling of homogeneous dams and other earthworks should also be carried out with the necessary care, since the exit of the pond beyond the specified boundaries can lead to the deposition of soil fractions that do not meet the requirements of the project on the surface of the lateral zones of the structure, and the displacement of the pond to embankment often leads to its breakthrough and erosion of the slope of structures.

5.34. Depth measurements in the pond during the influx of the dam with the core are carried out once or twice a month on the control diameters - on the axis of the dam and on quarters of the width of the pond. Measurements are made from a raft or boat using a basting with a metal disc at the end with a diameter of 15 cm.

5.35. Systematically, at least every two or three days, the condition of the spillway wells and their extension, as well as other spillway devices, should be checked, about which an appropriate entry is made in the quality control log of alluvial work.

5.36. During alluvium in winter conditions, the thickness of the frozen layer washed with fresh soil is subject to control. It is necessary to control the timely removal of ice from the surface of the alluvium map (in case of its formation), the condition of the embankment and discharge devices, the size and position of the pond, as well as monitoring the implementation of other requirements of the project for the production of works in winter conditions.

According to a special task of the design organization or the technical management of the construction, the geotechnical service, after the end of the winter period of work and the thawing of the surface layer of soil, drills pits in order to determine the state of the soil in the structure.

5.37. During the construction of alluvial dams, systematic monitoring of the state of the slopes should be ensured in connection with the possibility of leakage of seepage water onto them. A filtration flow arises in the body of the building to be washed, which is formed due to the water loss of the washed soil, infiltration from the settling pond and from the slope of the alluvium, periodically covered with pulp flows. In the case of a high intensity of alluvium and with insufficient filtration capacity of the soil of the lateral zones, seepage of the filtration flow onto the slopes of the structure may occur, which can cause landslides and soil slumps.

5.38. Employees of the geotechnical service must daily inspect the slopes of the structure being washed and note all seepage water outlets. Dispersed and intermittent outflows of seepage water onto the slopes of the dam usually do not harm the structure, however, intensive outflows in the form of keys can cause landslides or slumps, especially in fine-grained soils. Observations of seepage water outlet should be linked to control over the condition of the settling pond. The marks of the upper boundary of seepage water outlets are entered in the working journal-diary, they must be recorded simultaneously with the marks of the level of the pond and its dimensions.

In threatening cases, the head of the geotechnical service must demand that the organization producing the alluvium reduce the intensity of the alluvium and, in extreme cases, temporarily stop work in the area where seepage water seeps out.

5.39. The geotechnical service must monitor the condition of permanent drainage devices provided for by the construction project and built before alluvium or being built simultaneously with alluvial work. Clogging or washing out of these devices during the production of alluvium is not allowed. All violations of drainage devices must be immediately brought to the attention of the representative of the organization producing the alluvium of the structure and the chief construction engineer for the latter to take the necessary measures to restore these devices.

5.40. When signs appear that indicate abnormal settlements of the base or body of the structure (cracks, landslides on slopes, local soil subsidence, sharp increases in the settlement of control benchmarks, etc.), the geotechnical service must immediately notify the heads of the organization conducting the alluvium, and the chief construction engineer, to demand extraordinary geodetic measurements and involve the geological service in the survey of the structure in order to take measures to eliminate the detected deformations.

5.41. The geotechnical service should mark all gullies on the outer slopes of the dam, which occur when the rules for the production of work are violated, when, due to erosion of the embankment, the pulp flow breaks through to the outer slope. At the same time, the composition and volume of the soil with which the gullies are sealed are indicated and samples are taken for the density of this soil.

5.42. If the design of the dam provides for the installation of control and measuring equipment (benchmarks, piezometers, etc.), then the geotechnical service is obliged to monitor the installation and condition of this equipment. In some cases, the geotechnical service may be entrusted with monitoring the level of seepage water using piezometers.

5.43. The duties of the geotechnical service include periodically determining the magnitude of the slopes of the surface of the reclaimed soil above and below the water level in the settling pond; the frequency is set according to SNiP 3.02.01-87 (Table 13). The measurement of the slopes of the surface surface is carried out in accordance with the instructions of clause 5.29, and under water - by measuring the depth of the water in the pond along the alignment of the rails. The ground surface elevation is obtained as the difference between the pond water level and the water depth.

5.44. The geotechnical service should provide control over the thickness of the soil washed in per day (intensity of alluvium). When alluvium of structures from silty and clay soils or structures erected on an impervious foundation, the excess of the design daily intensity of alluvium must be agreed with the design organization. In special cases (when it is provided for by the project and the Specifications), the density and moisture content of alluvial layers of soil are controlled depending on the duration of breaks in alluvium.

Construction dewatering
5.45. Construction dewatering is used in earthworks during the construction of foundations, hydraulic structures, underground workings, communications, as well as in other works in water-saturated soils.

The essence of the method lies in the fact that when pumping groundwater by various methods (water-reducing wells, wellpoints, open drainage), the surface of the water in the soil acquires a funnel-shaped shape, while lowering to the place of pumping.

5.46. The task of construction dewatering is to create and maintain a depression funnel in aquifers during the construction period, where pits are laid, as well as to relieve excess pressure in the underlying aquifers separated from the base of the pit by an aquiclude.

5.47. The production of dewatering works can affect the change in the initial properties of the soil. Pumping out water in the ground leads to an increase in pressure from its own mass and to additional precipitation of the territory. This is especially true for soft soils, the precipitation of which can cause unacceptable deformations of structures built within the water pumping zone.

A change in soil properties can also be caused directly by drilling wells, especially if the dewatering must be carried out to a great depth in highly permeable soils, when a large number of wells are required, the drilling of which affects the properties of the surrounding soil.

5.48. Dangerous soil disturbances can also occur during open drainage. These include the removal of fine particles on the slopes, as well as swelling of the bottom of the pit due to hydrodynamic weighing.

%D0%AD%D0%BD%D0%B5%D1%80%D0%B3%D0%B5%D1%82%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0 % B0% D1% 8F% 20% D0% BE% D1% 82% D1% 80% D0% B0% D1% 81% D0% BB% D1% 8C -> Rules for the organization of commissioning for process control systems at thermal power plants RD 34 35. 414-91 Valid from 01. 07. 91 to 01. 07. 98

Page 4 of 13

3. CONSTRUCTION OF EMPIDS BY THE METHOD OF FILLING SOILS INTO WATER

3.1. The method of filling soils into water is used for the construction of dams, dams, impervious elements, pressure structures in the form of screens, cores, droops and backfilling at the interfaces of earthworks with concrete. For the construction of an embankment by dumping soils into the water and preparing a foundation for it and interfaces with the banks, the design organization must develop technical conditions, including requirements for the organization of geotechnical supervision.

3.2. The filling of soils into water should be carried out in a pioneering way, both in artificial, formed by embankment, and in natural reservoirs. Backfilling of soils into natural reservoirs without the installation of bridges is allowed only in the absence of flow rates that can erode and carry away small fractions of the soil.

3.3. Soil dumping should be carried out by separate maps (ponds), the dimensions of which are determined by the project for the production of works. The axes of the maps of the stacked layer, located perpendicular to the axis of the structures, should be shifted relative to the axes of the previously laid layer by an amount equal to the width of the base of the embankment dams. Permission to create ponds for filling the next layer is issued by the construction laboratory and technical supervision of the customer.

3.4. When filling an embankment into natural reservoirs and ponds with a depth of up to 4 m from the water's edge, the preliminary thickness of the layer should be determined from the conditions of the physical and mechanical properties of the soils and the availability of a dry soil reserve above the water horizon to ensure the passage of vehicles according to Table. 2.

table 2

Sing thickness	Carrying capacity of transport	Dry soil layer, cm, above the horizon water in the pond during filling
dumping, m	funds, t	sands and sandy loams	loams

The thickness of the backfill layer is adjusted during the construction of embankments.

At depths of natural reservoirs from the water's edge over 4 m, the possibility of dumping soils should be determined empirically in production conditions,

3.5. The embankment dams within the erected structure should be made from the soil laid in the structure. Transitional layers or filters with screens on the inner slope made of waterproof soils or artificial materials can serve as longitudinal embankment dams.

The height of the embankment dams should be equal to the thickness of the layer being poured.

3.6. When filling soils, the water horizon in the pond should be constant. Excess water is diverted to the adjacent card through pipes or trays or pumped to the overlying card by pumps.

Backfilling should be carried out continuously until the pond is completely filled with soil.

In the event of a forced break in work for more than 8 hours, the water from the pond must be removed.

3.7. Compaction of the dumped soil is achieved under the influence of its own mass and under the dynamic influence of vehicles and moving mechanisms. In the process of dumping, it is necessary to ensure uniform movement of vehicles over the entire area of ​​the dumped map.

3.8. When transporting soil with scrapers, dumping soil directly into the water is not allowed. In this case, the dumping of soil into the water must be carried out by bulldozers.

3.9. With an average daily air temperature of up to minus 5 °C, work on dumping soil into water is carried out according to summer technology without special measures.

When the outside air temperature is from minus 5 °C to minus 20 °C, soil filling should be carried out according to winter technology, taking additional measures to maintain a positive soil temperature. Water in the pond must be supplied with a temperature above 50 ° C (with an appropriate feasibility study)

3.10. The sizes of maps when working on winter technology should be assigned from the conditions of preventing a break in work; backfilling of soils on the map must be completed within one continuous cycle.

Before filling the cards with water, the surface of the previously laid layer must be cleared of snow and the upper crust of the frozen soil must be thawed to a depth of at least 3 cm.

3.11. When dumping soil into water, the following should be controlled:

fulfillment of project requirements and technical conditions for the construction of structures by dumping soil into water;

compliance with the design thickness of the backfill layer;

uniform compaction of the surface layer of soil by moving vehicles and mechanisms;

compliance with the design depth of water in the pond;

the surface temperature of the base of the dump map and the water in the pond.

3.12. Samples to determine the characteristics of soils should be taken one for every 500 m 2 of the area of ​​​​the poured layer (underwater) with a thickness of more than 1 m - from a depth of at least 1 m, with a layer thickness of 1 m from a depth of 0.5 m (from horizon of water in a pond).

Content

3.1. The method of filling soils into water is used for the construction of dams, dams, impervious elements, pressure structures in the form of screens, cores, levels and backfilling in conjunction with earth structures with concrete. For the construction of an embankment by dumping soils into the water and preparing a foundation for it and interfaces with the banks, the design organization must develop technical conditions, including requirements for the organization of geotechnical supervision.

3.2. The filling of soils into water should be carried out in a pioneering way, both in artificial, formed by embankment, and in natural reservoirs. Backfilling of soils into natural reservoirs without the installation of jumpers is allowed only in the absence of flow rates that can erode and carry away fine fractions of the soil.

3.3. Soil dumping should be carried out by separate maps (ponds), the dimensions of which are determined by the project for the production of works. The axes of the maps of the stacked layer, located perpendicular to the axis of the structures, should be shifted relative to the axes of the previously laid layer by an amount equal to the width of the base of the embankment dams. Permission to create ponds for filling the next layer is issued by the construction laboratory and technical supervision of the customer.

3.4. When filling an embankment into natural reservoirs and ponds with a depth of up to 4 m from the water's edge, the preliminary thickness of the layer should be determined from the conditions of the physical and mechanical properties of soils and the availability of a supply of dry soil above the water horizon to ensure the passage of vehicles according to Table. 2.

table 2

Sing thickness	Carrying capacity of transport	Dry soil layer, cm, above the horizon water in the pond during filling
dumping, m	funds, t	sands and sandy loams	loams

The thickness of the backfill layer is adjusted during the construction of embankments.

At depths of natural reservoirs from the water's edge over 4 m, the possibility of backfilling soils should be determined empirically in production conditions,

3.5. Embankment dams within the erected structure should be made from the soil laid in the structure. Transitional layers or filters with screens on the inner slope made of impervious soils or artificial materials can serve as longitudinal embankment dams.

The height of the embankment dams should be equal to the thickness of the layer being poured.

3.6. When filling soils, the water horizon in the pond must be constant. Excess water is diverted to the adjacent card through pipes or trays or pumped to the overlying card by pumps.

Backfilling should be carried out continuously until the pond is completely filled with soil.

In the event of a forced break in work for more than 8 hours, the water from the pond must be removed.

3.7. Compaction of the dumped soil is achieved under the influence of its own mass and under the dynamic influence of vehicles and moving mechanisms. In the process of dumping, it is necessary to ensure uniform movement of vehicles over the entire area of ​​the dumped map.

3.8. When transporting soil by scrapers, dropping soil directly into the water is not allowed. In this case, the dumping of soil into the water must be carried out by bulldozers.

3.9. At an average daily air temperature of up to minus 5°C, work on dumping soil into water is carried out according to summer technology without special measures.

When the outside air temperature is from minus 5°C to minus 20°C, soil filling should be carried out according to winter technology, taking additional measures to maintain a positive soil temperature. Water in the pond must be supplied with a temperature above 50 ° C (with an appropriate feasibility study)

3.10. The dimensions of the cards when working according to winter technology should be determined from the conditions of preventing a break in work; backfilling of soils on the map must be completed within one continuous cycle.

Before filling the cards with water, the surface of the previously laid layer must be cleared of snow and the upper crust of the frozen soil must be thawed to a depth of at least 3 cm.

When dumping soil into water, the following should be controlled:

fulfillment of project requirements and technical conditions for the construction of structures by dumping soil into water;

compliance with the design thickness of the backfill layer;

uniform compaction of the surface layer of soil by moving vehicles and mechanisms;

compliance with the design depth of water in the pond;

the surface temperature of the base of the dump map and the water in the pond.

3.12. Samples to determine the characteristics of soils should be taken one for every 500 m 2 of the area of ​​​​the poured layer (underwater) with a thickness of more than 1 m - from a depth of at least 1 m, with a layer thickness of 1 m - from a depth of 0.5 m (from the water horizon in the pond).

Overlapping methods and areas of their application

Blocking the river bed during the construction of a river hydroelectric complex is one of the most difficult stages of work in the general scheme for skipping construction costs. The essence of the overlapping process is to switch the flow of water in the river to the drainage tract (various openings, tunnels, channels) prepared in advance at stage I by gradually or instantly blocking the channel with various materials (sand and gravel mixture, rock mass, sorting stone, special concrete elements (cubes , tetranuclei, etc.), (Fig. 2.13).

The channel is blocked by the following methods (Fig. 2.14): frontal backfilling of a stone banquet into flowing water (frontal method); pioneer dumping of a stone banquet into flowing water (pioneer method); alluvium of sandy-gravel soil by means of hydromechanization (alluvial method); instantaneous collapse into the channel of earthen or rock masses (directed explosion method); other special methods (dropping large concrete masses or capsizing them, flooding floating structures, driving sheet piles, immersing wattle or straw mattresses, etc.).

The most common ways of blocking the river bed are the frontal and pioneer methods of backfilling a stone banquet into the water. The complexity of overlapping when applying these methods depends mainly on two factors: the maximum flow velocity in the gap Umax and the maximum specific flow power

Thus, the maximum speeds with frontal overlap are much lower than with pioneer overlap (with the same final differences DZKOH). Therefore, it has the advantage of being used for blocking rivers with easily eroded soils in their channels. But its use is complicated by the need to build a bridge across the hole to fill the banquet. When using the pioneer method of overlapping, on the contrary, the hydraulic conditions in the channel become more difficult, but the organization and production of work are simplified, and a bridge is not required.

The choice of the method of overlapping, in principle, should be carried out on the basis of a technical and economic comparison of options.

The greatest influence on the choice of the method of overlap is exerted by the natural geological and hydrological conditions in the alignment of the overlap. From hydrological

The timing of the blocking of the channel is timed to coincide with low water periods and is usually set at the end of the shipping period in the autumn-winter months.

Channel overlap calculations

Justification of the channel blocking option should be accompanied by a number of relevant calculations.

In general, hydraulic and other calculations to justify the blocking of the channel include: determination of the permissible preliminary restriction of the river channel before the opening of the barriers; determination of the final drop at the Akon banquet; control over changes in the hydraulic characteristics of the flow (flow rate Q, differentials AZ, velocities in the hole, total and specific flow rates N and N°) in the hole and on the structures during the closing process; determination of the size of the stone required to close the hole at different stages; determination of the volume of stone of various sizes.

All these calculations are performed using the laws of hydraulics and computer programs.

Organization of work on blocking the channel

The blocking of the channel can be divided into the following stages: preparatory, preliminary constraint of the channel, closing the gap and final.

At the preparatory stage, work is carried out to organize warehouses for materials, to build roads (and, if necessary, bridges) from warehouses to the alignment of the overlap, to prepare transport and loading facilities, to arrange lighting for the overlap area, to organize a hydrological service and other work that ensures successful and timely blocking of the channel. These works are completed in 1-2 months. before closing the gap in parallel with the main work on the construction of structures in the pit of the 1st stage.

Preliminary restriction of the channel provides for the narrowing of the blocked channel to allowable conditions for navigation and erosion of the channel while maintaining the design opening. This restriction of the channel with all methods of blocking is carried out by the pioneer filling of a stone banquet from the banks (from one or two) or by alluvium of sandy-gravel soil.

To improve the conditions for overlapping with easily eroded soils in the channel, preliminary fixing of the bottom with low-erosion soil (as a rule, rock mass or stone) is provided by dumping this soil from floating craft. Fastening is carried out along the entire width of the hole 5-10 m upstream and 50-100 m downstream from the axis of the banquet, depending on the base soils and the conditions of their erosion when the channel is constrained.

To avoid subsequent erosion, the thickness of the fastening should be at least 3 diameters of the stone being poured. In parallel with these works, at this stage, the preparation of the entire drainage tract in the pit of the 1st stage and the compression of the jumpers are being carried out.

The overlapping of the channel opening is the most crucial moment in the entire stage of overlapping and begins with the dismantling of the 1st stage cofferdams, flooding the pit and switching part of the flow from the channel to spillways. In this case, special attention should be paid here to the thoroughness of disassembling the jumpers to the design dimensions. With insufficient disassembly of the jumpers, the total difference during overlapping can significantly exceed the main design difference at the structure, which complicates the overlap.

After the opening of the bridges, part of the flow is switched to spillways, the flow, drops and velocities in the channel fall, which makes it possible to start closing the gap with the same material that was used in the banquet during the preliminary constraint (usually rock mass). Since the speed in the gap after the start of backfilling gradually increases as the gap narrows and the difference increases, material of different sizes should in principle be used for backfilling at different stages of overlap. However, in practice, two types of materials are most often used. At the initial stage, rock mass is used, and at the final stage, a large stone (oversized) and various concrete elements (cubes, tetrahedra, reinforced concrete hedgehogs, etc.) are used. The higher the difference in overlapping and the specific power of the flows, the larger the dumped elements should be in principle.

When rivers with weakly eroded and non-eroded channels are blocked, the differences reach significant values. Thus, during the pioneering closure of the Angara in the alignment of the Ust-Ilimskaya HPP, the maximum drop reached 3.82 m at a flow rate of 2970 m3A and a specific flow power of 900 kW. At the last stage, bundles of oversized pieces with a total mass of up to 25 tons were used to block the gap at the last stage. Chirchik (Charvak HPP) the difference reached 4.2 m, and the rivers Vilyui (Vilyui HPP) and Naryn (Toktogul HPP), respectively, 5 and 7.32 m. 10 tons, at the Vilyui HPP - large-block stone weighing up to 25 tons, and at the Toktogul HPP - concrete tetrahedra weighing 10 tons and stone blocks up to 25 tons.

In order to reduce the drops and velocities in the gap with the pioneering method, it is possible to use two-banquet overlap schemes, dispersing the total drop into two banquets.

With the frontal method, an additional element of organizing the overlap of the hole is the need for transport communications to be able to dump the material simultaneously across the entire width of the hole. Usually floating bridges are arranged for these purposes (Fig. 2.18). Ropeways, cable cranes and fixed bridges are sometimes used. Dumping of materials from bridges is carried out using dump trucks with end or side unloading, for which they must be specially prepared. The width of the bridges should ensure free maneuvering of vehicles when unloading the stone. At end unloading of dump trucks with a carrying capacity of 5-15 tons, it is 18-20 m, with side unloading - 10-12 m. clear regulation of the movement of vehicles to the places of dumping based on the results of measurements. The intensity of dumping during the blocking of large rivers reaches 1000-1300 m / h (Volzhskaya named after the XXII Congress of the CPSU, Saratov, Krasnoyarsk hydroelectric power stations), and the number of car trips is up to 360 per hour (Saratovskaya hydroelectric power station).

As with the pioneer method, at the initial stage, rock mass is used for backfilling, and at the final stage, oversized and concrete elements are used. So, on the ceilings of the channels during the construction of the Kamskaya and Votkinskaya HPPs with drops, respectively, of 1.4 and 1 m, concrete cubes weighing up to 5 tons were used, the Volga HPPs with drops up to 2 m - concrete tetrahedra weighing up to 10 tons, and the Gorkovskaya HPP with a drop 0.9 m-concrete cubes weighing up to 5 tons and reinforced concrete hedgehogs weighing 0.6 tons.

At the final stage, after the direct closure of the opening, the banquet is filled up to the design profile of the required design. The overlap banquet is usually included in the downstream drainage dam of the dam with appropriate filters and is located in its place.

If there is a foundation pit of the 2nd stage, the floor banquet, as a rule, is part of the future transverse overhead lintel and is located in its place. In this case, immediately after the overlap, this jumper is erected to the marks corresponding to the water level during the overlap, and later (to the flood) to the marks corresponding to the omission of the estimated construction flow. In parallel, a lower transverse lintel is being erected.

Since the overlap is usually carried out in late autumn, it is very important at this stage to quickly and timely organize a pit of the 2nd stage and, before the onset of cold weather, pump it out and excavate loose soils. Otherwise, the development of saturated sandy-gravelly soils after their freezing will significantly complicate and increase the cost of excavation in winter conditions.

An example of the overlap of large rivers in the last period is the overlap of the river. Yangtze at the construction of the Three Gorges hydroelectric complex in China. The blocking of the river was carried out in November 1997. And it took place under conditions that the practice of world hydraulic construction did not know.

One of the essential features of the overlap in the alignment of the hydroelectric complex is the great depth of the river; the maximum depth reached 60 m, which complicated the work. The overlap project provided for the simultaneous restriction of the channel from both banks of the river using dump trucks with a carrying capacity of 44 - 77 tons. The width of the cofferdam (banquet) on top was 30 m, which made it possible for three dump trucks to work simultaneously in parallel. As a result, the rock dumping rate was 194,000 m3/day, or 17,100 m3/h. In total, 208,000 cubic meters of rock were poured into the hole. The width of the hole is 40 m, the depth is 60 m.

The actual flow of the river during the closure was 11,600 m3/s, the maximum drop was 0.66 m, and the maximum flow velocity was 4.22 m/s. The discharge of discharges during the blocking was carried out through 23 bottom spillways with a cross section of 79 m in the spillway sections of the dam. In general, the dam is designed to allow a flow rate of 0.1% during operation equal to 116,000 m3/s with a test for a flow rate of 0.01%. The total length of the spillway sections of the dam is 483 m. The dam has 23 bottom spillways with a cross section of 79 m and 22 surface spillways with a span of 8 m.