Fundamentals of hydropower. Arch dams. A dam is a structure used from antiquity to the present day. What is a dam?

According to their purpose, dams are divided into reservoir, water-lowering and water-lifting dams. The water level back-up at water-raising dams is low; the purpose of constructing such dams is to improve the conditions for water intake from the river, the use of water energy, etc. Reservoir dams are distinguished by a noticeably higher height, as a result, a larger volume of the created reservoir. A distinctive feature of large reservoir dams is the ability to regulate flow; small dams, which are used to create, for example, ponds, do not regulate flow. Most often, such a functional division of dams into reservoir and water-lifting ones is conditional, due to the difficulty of determining a more important function. Instead, dividing dams according to the height of water rise can be used: low-pressure (water depth in front of the dam is up to 15 m), medium-pressure (15-50 m), high-pressure (more than 50 m).

Dams are built across rivers and rivers in order to raise the water level and form an artificial waterfall, which is used as a mechanical force or to make small rivers navigable and spread shipping and rafting further up the river.

Streams, ravines, ravines and hollows are blocked by dams to retain rain and snow water in them, forming ponds and reservoirs, the reserves of which are used in the dry season for irrigating fields, for watering and other household needs, or for water supply to populated areas, for feeding shipping canals, as well as for passing water into rivers when they are not deep enough for navigation (the Msta, Upper Volga and others rivers).

Dams are built along rivers to direct the flow according to the needs of navigation, and along the banks of rivers, lakes and seas - to protect against floods and to prevent the intrusion of sea waters into the country.

Dam classification

The type and design of the dam are determined by its size, purpose, as well as natural conditions and the type of main building material. Dams differ in the type of base material from which they are built, their purpose and the conditions for the passage of water.

By material type

Dams are classified according to the type of base material:

By construction method

• bulk
• alluvial
• directed explosion

According to the method of perception of the main loads

• gravitational
• arched
• buttress
• arched-gravity

According to the conditions for passing water flow

• deaf (do not allow water to overflow over the ridge)
• spillway
• filtering (water is passed through the body of the dam)
• overflow (catastrophic action)
• collapsible

Story

The art of constructing dams has been known since ancient times. Herodotus mentions water-raising dams. Abu-l-Fida reports a dam built by the Persians to divert water from the city of Tostara. Abbas I the Great built a stone dam near Kashan 36 meters long, 16 m high and 10 m thick, equipped with a channel at the base to allow water to pass through. Finally, in ancient times very large dams were also built to protect areas from floods, for example, by the Arabs in the 2nd century AD. e. Similar work, according to the story of Abu-l-Fida, was undertaken by Alexander the Great to prevent the overflow of Lake Cadiz near the Syrian city of Emesa.

The oldest known dam dates back to 3000 BC. It was located one hundred kilometers from Amman; it was a stone wall 4.5 meters high and 1 meter thick. In 2800/2600 BC, a dam with a length of 102 meters was erected 25 kilometers from Cairo; it was soon destroyed by a rainstorm. In the mid-3rd century, an entire system was built near the Indian city of Dholavira. The Romans built a wide variety of dams, primarily to provide reservoirs for dry periods; the highest Roman dam reached 50 meters in height and was destroyed only in 1305.

Since 1998, in dozens of countries around the world, every year on March 14, at the initiative of the International Rivers Network, the “International Day of Action Against Dams” (otherwise: “ Day of Action for Rivers, Water and Life""). Anti-dam activists have already achieved real results: two sixty-meter dams have been dismantled in the United States, and a law has been passed in Sweden that prohibits the construction of dams more than fifteen meters in height.

Gravity dams

Gravity dams absorb pressure from masses of water with their mass. Shear resistance occurs due to frictional forces or adhesion of the dam base along the base. As a result, such dams are massive in nature, often close to a trapezoidal cross-section in cross-section.

Arch dams

Arched dams transfer pressure from masses of water to the banks of the gorge (less often to artificial abutments). Because of this, such dams are more often built in mountainous areas, where the banks are composed of durable rocks. The arched structure transfers part of the loads to the base. Moreover, the wider the arch, the greater the pressure on the base. This requires an increase in the width of the dam in the lower part, and leads to the appearance of arch-gravity dams. Arch dams with buttresses at the bottom of the arch are called arch-buttress dams. In them, the work of the arch is limited to the upper part, which allows the use of arch dams in a wider range of locations.

Arch gravity dams

Arch-gravity dams combine the properties of arch and gravity dams.

Buttress dams

Just like arch dams, they can reduce the weight of the dam body and its dimensions due to a more efficient design scheme. The wall in a buttress dam is thinner than in a gravity dam due to its reinforcement on the downstream side with retaining structures (walls).

Earth dams

A soil or earthen dam is built from soil materials, including sandy, loamy, clayey, as a rule, without water overflowing through it. Typically the cross-sectional shape approaches trapezoidal. Earth dams are simple in design and can be constructed in a very wide range of geological conditions. Taking this into account, as well as the use of local building materials in the construction of the dam, almost complete mechanization of labor and reduction of labor costs, earth dams can be considered the most common type of water-retaining structure. Earth dams are classified as gravity dams.

Earth dams were among the very first dams in human history. For a long time, such dams have been built in Russia. The Zmeinogorsk dam of the 18th century, built by the outstanding Russian engineer Kozma Frolov, is famous.

Modern earth dams reach very large sizes, for example, the Nurek dam reaches a height of three hundred meters, and the Tarbela dam has a volume of 130 million cubic meters. The geography of the dams is extremely wide: the Vilyuiskaya, Ust-Khantaiskaya, Kolyma dams were built in permafrost conditions, the world's highest Rogun dam is being built in Central Asia, there are dams in the Caucasus - Sarsangskaya, Mingachevirskaya, dams are known in the Far East, the Carpathians, and the Crimea.

Classification of earth dams

Earth dams are classified according to the material of the dam body, design, method of work, height, type of anti-seepage devices at the base.

Dams up to 25 meters high are considered low, dams in the range of 25-75 meters are considered medium, and dams above 75 meters are high dams. Particularly high dams (more than 150 m) are classified as “super high”.

Material	Dam design type
	Homogeneous	With central core	with screen	with diaphragm
Zemlyannaya
	Construction method: soil filling with layer-by-layer compaction; alluvium; explosion outline	Construction method: alluvium; backfill	Construction method: alluvium; backfill	Construction method: alluvium; backfill
Stone-earth
		Construction method: backfill; sketch; alluvium	Construction method: backfill; sketch
Stone
	Construction method: explosion sketch; backfill		Construction method:	Construction method: backfill; sketch; explosion outline

Calculations of earth dams

When designing modern soil dams, calculations are carried out taking into account the stress-strain state under static and dynamic influences. When carrying out calculations, computers are used, and the design engineer requires knowledge of the theory of elasticity and plasticity, creep, and numerical methods. The work of the soil is modeled taking into account its most important properties, and the use of continuum mechanics methods allows one to obtain calculation results that are very close to reality. Modern design of earth dams sometimes takes into account the rheology of soils.

When designing dams, several groups of calculations should be carried out, including:

• calculations of filtration in the dam body;
• calculations of the dam foundation;
• calculations of the dam body;
• calculations related to seismic resistance;
• calculations of the stability of dam slopes;
• calculations of the interface between the dam and the foundation.

Calculations of filtration in the dam body are necessary to carry out other calculations, for example, slope stability. The seepage flow through the dam affects the operation of the dam as a whole. The filtration flow parameters determine the design of both the dam and associated devices. During the calculation of filtration, the speed of moving groundwater, filtration flow rates through the dam body are determined, a hydrodynamic grid of filtration flow movement and a depression surface (the upper limit of the filtration flow in the dam body) are constructed.

When calculating the foundation, the settlement of the foundation, the bearing capacity of the soil are determined, and the compaction (consolidation) of the foundation is predicted.

Calculations of the dam body determine its settlements, check the strength of soil materials, and assess crack formation.

Soil dam structures

The design of the dam is largely determined by the properties of local soils available near the site. The design is also influenced by the engineering-geological situation of the construction site, the hydrological characteristics of the river and runoff, climatic conditions, seismicity of the area, and the availability of a fleet of necessary construction machines.

During the design, the following tasks are solved:

• the overall dimensions of the structure are assigned (dam height, slopes, crest width, berm dimensions);
• the type of strengthening of slopes and ridges is selected;
• anti-filtration devices in the dam body are determined;
• drainage devices are being developed;
• the underground contour of the dam is being constructed;
• the type of connection between the dam and its foundation and banks is assigned.

Dam failures and safety

The damage from a dam failure can be extremely large. This is due to the fact that the destruction of the dam structure itself is often only a small part of the total damage, which includes losses from the destruction of associated structures (since the dam is almost always only part of a hydraulic system), losses of enterprises where production may be paralyzed as a result of the cessation of revenues from hydroelectric power stations, losses from destruction caused by a catastrophic spillway in the downstream of the dam.

Major dam disasters

List of some major disasters that occurred at dams.

date	Dam	Place	Death toll	Photo
March 12, 1928	St. Francis Dam	San Francisco Canyon, Coast Ranges, USA	about 600 people	The dam before the disaster.	A piece of concrete from a structure half a mile from the broken dam (the piece is approximately 3 meters high). The dam itself is visible in the distance.
August 18, 1941 autumn 1943	Dneproges	Zaporozhye, USSR	From 20 to 100 thousand people. The German command estimated its manpower losses at 1,500 people. . These numbers are not supported by any documents.	Dnieper hydroelectric station in the summer of 1942.	Destruction after the explosion of a hydroelectric power station in 1943.
December 2, 1959	Malpasse Dam	Côte d'Azur, France	423 people		Remains of the dam.
October 9, 1963	Vayont Dam	Monte Toc, Belluno, Italy	2500 people	Dam design.	The city of Longarone after the passage of a catastrophic wave.
August 7, 1975	Bainqiao Dam	Zhumadian, China	171 thousand people		External images [?url=http://img-fotki.yandex.ru/get/5816/86906606.18/0_69ee9_85d10ad5_L The dam after destruction.] (Arch. source 2012-04-30)

Security

In the Russian Federation, the safety of hydraulic structures is regulated by the Federal Law “On the Safety of Hydraulic Structures”, adopted by the State Duma on June 23, 1997. Dams must be designed in accordance with current regulatory documents: construction norms and rules (SNiPs), State Standards (GOSTs), departmental regulatory documents (RD).

Safety measures must be taken from the design stage. During the construction of the dam, a check must be made to ensure that the work, the properties of the foundations and building materials comply with the design data. During the operation of the structure, it is necessary to carry out field observations - monitoring the dam using instrumentation. The installation of equipment in a structure should be provided for at the design stage and, depending on the class of the structure, should provide monitoring of precipitation, horizontal displacements, parameters of filtration flow in the dam body, temperature, stress-strain state, etc.

In addition to hardware monitoring, full-scale visual and

Dam

a hydraulic structure that blocks a river (or other watercourse) to raise the water level in front of it, concentrate pressure at the location of the structure and create a reservoir. The water-economic importance of P. is diverse: the rise in water level and the increase in depths in the upper pool favor shipping, timber rafting, as well as water intake for the needs of irrigation (See Irrigation) and water supply (See Water supply). ; the concentration of pressure near the river creates the possibility of energy use of river flow; the presence of a reservoir makes it possible to regulate the flow, i.e., increase the water flow in the river during low-water periods and reduce the maximum flow during a flood, which can lead to destructive floods. The river and the reservoir significantly affect the river and adjacent territories: the river flow regime, water temperature, and the duration of freeze-up change; fish migration becomes difficult; the banks of the river in the upper pool are flooded; The microclimate of coastal areas is changing. P. is usually the main structure of a waterworks complex (See Waterworks).

Dam engineering arose as long ago as hydraulic engineering , in connection with the significant development of artificial irrigation of territories among the agricultural peoples of Egypt, India, China and other countries. The construction of P. was required for the construction of hydraulic power plants, and then the construction of hydroelectric power stations. The energy use of water resources was the main incentive for increasing the size and improving the design of waterways and the appearance of hydraulic structures on high-water rivers.

On the territory of the USSR, water mills with water were built back in the days of Kievan Rus. In the 17th-19th centuries. mining, metallurgy, textile, paper and other industries in the Urals, Altai, Karelia and central regions of Russia used mainly the mechanical energy of hydraulic power plants; their buildings were small in size and were constructed from local materials. Powerful hydroelectric power stations with large concrete and earthen pumps began to be built only under Soviet power, after the adoption of the GOELRO plan. In 1926, the first concrete spillway of the Volkhov hydroelectric power station was built. In 1932, a high concrete P. Dnieper hydroelectric power station was built (its maximum height is about 55 m). The spillway reservoir of the Nizhnesvirskaya hydroelectric power station is the first reservoir built on weak clay soils. In the 50-70s. on high-water rivers were built: alluvial earthen P. on the Volga near Kuibyshev and Volgograd, concrete P. Bratsk hydroelectric power station on the Angara (height 128 m) and the Krasnoyarsk hydroelectric power station on the Yenisei (124 m) (rice. 1 ), a high 300-meter stone-earth P. Nurek hydroelectric power station on the river. Vakhsh, arched P. Sayan hydroelectric power station on the Yenisei (height 242 m, ridge length 1070 m; is under construction, 1975) and many others. The design and construction of dams in the USSR are distinguished by a high technical level, which allowed Soviet dam construction to occupy one of the leading places in the world.

Of the P. built abroad, it should be noted: multi-arched P. Bartlett, height 87 m(USA, 1939), stone P. Paradella, height 112 m(Portugal, 1958), earthen P. Ser-Ponson, height 122 m(France, 1960), stone-earth P. Miboro, height 131 m(Japan, 1961), gravity concrete P. Grand Dixence, height 284 m(Switzerland, 1961).

The type and design of a building are determined by its size, purpose, as well as natural conditions and the type of main building material. Based on their purpose, a distinction is made between reservoir reservoirs and water-lifting reservoirs (intended only for raising the level of the upper pool). Based on the pressure, pumps are conventionally divided into low-pressure (with a pressure of up to 10 m), medium pressure (from 10 to 40 m) and high-pressure (more than 40 m).

Depending on the role performed as part of a waterworks, the water supply can be: deaf, if it serves only as a barrier to the flow of water; drainage, when it is intended to discharge excess water flows and is equipped with surface drainage holes (open or with gates) or deep drainages; station, if it has water intake openings (with appropriate equipment) and water conduits feeding hydroelectric power station turbines. Based on the main material from which dams are built, a distinction is made between earthen dams (See Earthen dam), stone dams (See Stone dam), concrete dams (See Concrete dam), and wooden dams (See Wooden dam).

Earthen P. is constructed entirely or partially from low-permeability soil. Low-permeable soil laid along the upper slope of the P. forms a screen; When such soil is located inside the body of the soil, a core is created. The presence of a screen or core makes it possible to construct the rest of the pavement from permeable soil or from stone materials (stone-earth pavement). At the bottom of the lower slope of the earthen P., drainage is installed to drain water filtered through the body and base of the P. The upper slope of P. is protected from the effects of waves by concrete slabs or rock riprap. When constructing an earthen embankment, soil is extracted from a quarry using excavators, transported to the construction site by dump trucks, placed in the body of the structure, leveled with bulldozers, and compacted layer by layer with rollers. The construction of alluvial soil involves the development of soil by dredgers or hydraulic monitors, transportation of the pulp through pipes and its distribution over the surface of the constructed soil, after which the water drains away and the settling soil compacts itself. To prepare the foundation and erect an earthen P. in the river bed, its foundation pit is fenced off with a jumper. , and the river is diverted through pre-laid temporary conduits, which are closed after the construction of the P.

In stone (fill-fill) paving, the screen or central waterproof element (diaphragm) is made of reinforced concrete, asphalt, wood, metal, and polymer materials. The requirement of low water permeability also applies to the base of the P. If the base soil is permeable to a great depth, it is covered in front of the P. Ponur (for example, made of clay), forming one whole with the screen. P. with a core is complemented by a device at the base of a steel sheet pile wall or an anti-filtration curtain (See Anti-filtration curtain) . The stone in rockfill and rock-earth paving is poured in layers of great height.

Concrete floors are usually classified according to their design, depending on the shear operating conditions. ; Accordingly, there are 3 main types of P. ( rice. 2 ) - gravity dams (See Gravity dam), arch dams (See Arch dam), buttress dams (See Buttress dam). Basic The material for modern concrete floors (mostly gravity-based) is hydraulic concrete. One of the most important issues when constructing concrete substructures is reducing water filtration at the base. For this purpose, an anti-filtration curtain is installed at the base of a high concrete floor near the top edge. In the remaining section, the base is drained to reduce water pressure on the base of the floor, which increases the stability of the structure. To avoid the formation of cracks due to temperature fluctuations, gravity and buttress panels are cut lengthwise into short sections, the seams between which are covered with waterproof seals (see Waterproofing). To prevent the appearance of cracks as a result of shrinkage of concrete during hardening and to reduce thermal stresses, the concrete block is concreted in separate blocks of limited sizes; artificial cooling of the components of the concrete mixture and the concrete laid in the blocks is used by circulating coolant (from the refrigeration unit) through a system of pipes laid in the body of the concrete block. Concrete pavement in the river bed is usually constructed in 2 stages under the protection of lintels enclosing the pits. During the construction of the first stage of the river, the river flows along the free part of the riverbed; with the second - through the holes left in the P. (Proran y) , which are closed upon completion of all construction work. If the river bed is narrow, a concrete waterway is built in one step, with the river temporarily diverted into coastal waterways. Low-pressure concrete spillway dam, common in hydraulic engineering practice , erected on a non-rocky foundation and designed to pass large flows of water, has the design shown in rice. 3 . It is based on drainage spans formed by concrete Flytbet and Bulls and blocked by hydraulic gates (See Hydraulic gate) . Behind the spillways, a massive fastening of the channel is installed - Vodoboy (sometimes buried in the form of a water well), then there is a lighter fastening - Apron. Drainage is installed under the reservoir. The spillway is connected to the shores or earthen P. by massive abutments. A low-pressure concrete spillway is usually built using reinforcement, often the entire structure (see Reinforced concrete dam). In order to save material, flutbet and bulls of this kind are sometimes made of a lightweight cellular structure, with the cells filled with soil.

In forest areas, low-pressure wooden pumps of pile and cord construction are often built (usually they are equipped with spillways).

A special type of water-retaining structure is a collapsible navigable reservoir. To erect it in summer low water, buttresses made of steel trusses are installed on a flat surface, bridges are laid across them, on which gates of the simplest design rest. The port supports the level of the upper pool, and ships and rafts go through the lock. During high-water periods, gates and bridges are removed, buttress trusses are laid on the flatbet, opening the way for ships and rafts through the P.

The general trend of modern dam construction is to increase the height of the dam. Technically achieved heights can be exceeded, however, from an economic point of view, the construction of two successive dams of lower height often turns out to be more rational than one high one. Improvement of types of construction made from soil materials is carried out while simultaneously reducing the cost and speeding up their construction by increasing the power of construction mechanisms and vehicles. Increasing the efficiency of concrete floors is achieved by reducing their volume, replacing gravitational floors with buttresses, and the wider use of arched floors. This trend is accompanied by an improvement and specialization of the properties of cement and concrete. It is very effective to combine a spillway dam and a hydroelectric power station building in one structure, which ensures a reduction in the concrete (most expensive) part of the pressure front of the hydroelectric complex. This problem is solved both by placing hydraulic units in a high-pressure cavity and by using an underwater array of a low-pressure hydroelectric power station to install spillway openings in it.

Lit.: Grishin M. M., Hydraulic structures, M., 1968; Nichiporovich A. A., Dams from local materials, M., 1973; Moiseev S.N., Rock-earth and rock-fill dams, M., 1970; Grishin M. M., Rozanov N. P., Concrete dams, M., 1975; Production of hydraulic engineering works, M., 1970.

A. L. Mozhevitinov.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

Synonyms:

See what “Dam” is in other dictionaries:

On Lake Gordon This term has other meanings, see Dam (meanings). A dam is a hydraulic structure that blocks ... Wikipedia

DAM, a barrier built across a stream, river, estuary or part of the sea. The dam stores water and also regulates the supply of water for irrigation purposes. Dams also serve to prevent floods and as a basis for the operation of hydroelectric power plants.… … Scientific and technical encyclopedic dictionary

Dam, dam, pier, embankment, barrier, road. ... .. Dictionary of Russian synonyms and similar expressions. under. ed. N. Abramova, M.: Russian Dictionaries, 1999. dam dam, dam, pier, embankment, barrier, dam; jumper; hydraulic dam, dam... Synonym dictionary

Dam- Bratsk hydroelectric power station. DAM, a hydraulic structure that blocks a river (or other watercourse) to raise the water level in it, concentrate pressure at the location of the structure, and create a reservoir. Dams can be blind or spillway; ... Illustrated Encyclopedic Dictionary

DAM, dams, women. 1. A dam, a structure made of earth, stone, iron, concrete, etc., built across a river to raise the water level or across a ravine to form an artificial pond. “The miller’s water has sucked through the dam.” Krylov... ... Ushakov's Explanatory Dictionary

dam- A water-retaining structure that blocks a watercourse and its valley to raise the water level [GOST 19185 73] dam A water-retaining structure that blocks a watercourse and (sometimes) the valley of a watercourse to raise the water level. [SO 34.21.308 2005] dam... ... Technical Translator's Guide

dam- A hydraulic structure made of alluvial soil (earthen dam), stone, concrete (concrete dam), protecting the banks of rivers and seas from erosion and flooding, as well as creating backwater on reservoirs. → Fig. 80 Syn.: dam… Dictionary of Geography

A dam is a structure that helps block the rise of water or its flow for one purpose or another. The very first buildings of this type were discovered in Egypt, where they were used to create water storage facilities. Archaeologists from Germany found such an object two hundred kilometers from Cairo. It was a dam with its own name, "Sad el-Qaraf", which appears in the records of Herodotus. Experts disagree about her age. Some believe that it was built in 3200 BC, others believe that it was built between 2950-2750.

What was the oldest dam made of?

What size was the oldest dam? This impressive structure was a double stone wall, with additional stone fragments thrown between the sides. The length of the dam was more than 100 meters along the crest, and the height reached 12 meters. A similar project made it possible to accumulate up to two million cubic meters of water in Wadi al-Gharawi.

The Chinese built on a large scale and to last for centuries.

Some historians believe that dams were built everywhere at the points of development of one or another local civilization. For example, a stone structure dating back to the seventh century BC was found in Mesopotamia. In ancient Syria, similar structures were built one and a half thousand years before the birth of Christ. (Nahr el-Assi). Large-scale construction of dams was also observed in Ancient China. The master became famous here, and later Emperor Yu, to whom in 2283 BC the current ruler entrusted the management of all water construction in the empire. Under the leadership of the Great Yu (as he is still called), more than one dam was built. This was a large-scale construction that lasted for centuries and millennia, which made it possible by 250 BC to irrigate, for example, 50,000 square kilometers in the deserts of Sichuan using the waters of the Minjiang River. And it was in China that the practice of building hydraulic structures using an element such as an arch arose.

They were designed by da Vinci himself

In Europe, where the problem of irrigation was not as acute as in Asia and Africa, dams appeared much later - in the 16th century. Arched versions, in particular, are mentioned in Spanish chronicles in 1586, but engineers believe that the devices themselves could have been built centuries earlier. This is based on the fact that the geniuses of that time participated in their design - Leonado da Vinci, Malatesta, Mechini, as well as taking into account the accumulated experience that came to Europe after contacts with the Arab world. For example, it is known that even such a seemingly not very strong structure as an earthen dam was in use for a century before it collapsed (it was erected in France in 1196).

Use of dams in Rus'

For Rus', with its rich water resources, also, at first glance, there was no particular need for dams. However, they have existed here since the 14th century AD and were used in systems. The first mention of dams is noted in the will of Dmitry Donskoy, dating back to 1389. Peter the Great showed particular interest in such structures, so in the 18th century there were already more than 200 objects in the Russian Empire, among which the high earthen dam, Zmeinogorskaya, stood out. Water resources were transferred through such devices for use in textile, mining and other enterprises of the time.

A dam is something that can refer to one or another type of object depending on the classification. Today there are water storage, water lowering and lifting devices. Reservoir dams are usually very high and have the ability to regulate water release. Low structures (for example, for constructing ponds) usually do not have drainage. Another important classification is the division of objects depending on the depth of water before the dam. There are low-, medium- and high-pressure dams here (up to 15, 50 and more than 50 meters, respectively).

Dams for rivers and ravines

Dams on rivers can be built both across (to raise the water level, to create a waterfall, the power of which can be somehow used; to make shallow water passable for ships) and along (to protect against floods). In some cases, dams block streams, ravines, and hollows to retain melted snow water, which is then used for irrigation or to recharge shipping canals.

Main elements of a hydroelectric power station

Hydraulic structures usually include a dam, a reservoir before or after it, an installation for raising water, a complex of hydroelectric power stations, descents for the passage of fish, drainage of water (if the system is culverted), and structures for cleaning the system from sediment. Large objects are made of reinforced concrete, while small ones can be built from soil, metal, concrete, wood or even fabric. It is known that during the flood in Komsomolsk-on-Amur, the protective dam consisted of EMERCOM soldiers holding sheets of film on themselves, which prevented the water from overflowing over the tops of the existing protective structures.

How can dams take load?

Another classification of dams reflects how these objects resist loads. Gravity buildings absorb impacts with their entire mass and resist due to the adhesion of the base of the dam and the foundation on which it stands. Such options are usually very massive. For example, the hydroelectric dam on the Indus River (Tarbela Dam) has a height of about 143 meters and a length of more than 2.7 km, which creates a total volume of 130 million cubic meters. meters. Arched objects transfer pressure to the banks. If the arch is wide and the pressure is high, then gravity arch models or arches with buttresses at the base are used. Buttress options have a thinner dam wall, but a reinforced base due to supporting elements. Today, dams are built using the fill or alluvium method, as well as the directed explosion method.

Consequences of accidents

Accidents at dams entail significant material losses, since not only unique equipment is destroyed, but also enterprises that operate on electricity and water supplies from the dam are shut down. Sometimes entire settlements are washed away by water flows, crop areas are flooded, and crops are lost. But the worst thing is that tens, hundreds and even thousands of people can die almost instantly.

So, in March 1928, the destruction of the St. Francis dam occurred in the San Francisquito Canyon, then about six hundred people died, and multi-meter pieces of the dam itself were found at a distance of about a kilometer from the site of the breakthrough. In the USSR, during the Great Patriotic War (1941), a decision was made to deliberately blow up the Dnieper Hydroelectric Dam in connection with the occupation of Zaporozhye by fascist troops. The massive concrete structure was partially damaged by 20 tons of ammonal. How many people died then is still not precisely determined. They give figures from twenty to one hundred thousand people, including troops, refugees and the population that could be on the left bank of the Dnieper, which took the brunt of the water disaster.

The total number of victims is about 230 thousand people

Post-war accidents at dams at large power plants resulted in even greater casualties. In August 1975, when the Banqiao dam broke, 26,000 people were drowned alone, and taking into account the spread of epidemics and famine, the death toll reached 170-230 thousand people. At the same time, about a third of a million heads of livestock were destroyed and about 6 million buildings and structures were destroyed. The highway from Guangzhou to Beijing was closed for eighteen days. And all this happened because the dams, designed for maximum rainfall, could not withstand the onslaught of water masses brought by Typhoon Nina. On August 8, 1975, the smallest of the dams collapsed, which led to the release of water into Bancao, where 62 dams were broken in a short time. The resulting wave was up to 10 km wide and three to seven meters high. Some Chinese villages were completely washed away along with their inhabitants.

To prevent a dam from breaking, a number of measures are being taken today, including compliance with the dam design parameters, checking for compliance during work, observations during operation, collecting visual and geodetic information, etc. For dams, two non-compliances with the requirements of projects and standards are distinguished: “K1 " - the object has a potentially dangerous condition and urgent measures are needed to eliminate its causes, and "K2" - a pre-emergency condition, destruction is possible, rescue and evacuation work is needed.

Explanatory dictionary of the Russian language. D.N. Ushakov

dam

dams, railway

A dam, a structure made of earth, stone, iron, concrete, etc., built across a river to raise the water level or across a ravine to form an artificial pond. The miller's dam was leaked by water. Krylov. Wooden dam. Concrete dam.

trans. An obstacle, an obstacle to something. Create a dam against military danger.

Explanatory dictionary of the Russian language. S.I.Ozhegov, N.Yu.Shvedova.

dam

Y, f. A structure that blocks a river or current to raise the water level. Concrete village Zemlyanaya, wooden village Vodosbrosnaya village

adj. dam, -aya, -oe.

New explanatory dictionary of the Russian language, T. F. Efremova.

dam

A structure installed across a river or other body of water that blocks the flow and usually serves to raise the level of water in front of it.

trans. Something that interferes, prevents the development, manifestation of something.

Encyclopedic Dictionary, 1998

dam

a hydraulic structure that blocks a river (or other drainage) to raise the water level in it, concentrate pressure at the location of the structure or create a reservoir. A dam can be a dead dam, which only blocks the flow of water, or a spillway, designed to discharge excess water. Based on the main material, dams can be divided into earthen, stone, concrete, reinforced concrete, wooden and other dams.

Dam

a hydraulic structure that blocks a river (or other watercourse) to raise the water level in front of it, concentrate pressure at the location of the structure and create a reservoir. The water-economic importance of the river is manifold: the rise in water level and the increase in depths in the upper pool favor shipping, timber rafting, and water intake for irrigation and water supply needs; the concentration of pressure near the river creates the possibility of energy use of river flow; the presence of a reservoir makes it possible to regulate the flow, i.e., increase the water flow in the river during low-water periods and reduce the maximum flow during a flood, which can lead to destructive floods. The river and the reservoir significantly affect the river and adjacent territories: the river flow regime, water temperature, and the duration of freeze-up change; fish migration becomes difficult; the banks of the river in the upper pool are flooded; The microclimate of coastal areas is changing. P. is usually the main structure of a waterworks.

Dam construction arose as long ago as hydraulic engineering, in connection with the significant development of artificial irrigation of territories among the agricultural peoples of Egypt, India, China and other countries. The construction of P. was required for the construction of hydraulic power plants, and then the construction of hydroelectric power stations. The energy use of water resources was the main incentive for increasing the size and improving the design of waterways and the appearance of hydraulic structures on high-water rivers.

On the territory of the USSR, water mills with water were built back in the days of Kievan Rus. In the 17th-19th centuries. mining, metallurgy, textile, paper and other industries in the Urals, Altai, Karelia and central regions of Russia used mainly the mechanical energy of hydraulic power plants; their buildings were small in size and were constructed from local materials. Powerful hydroelectric power plants with large concrete and earthen pumps began to be built only under Soviet power, after the adoption of the GOELRO plan. In 1926, the first concrete spillway of the Volkhov hydroelectric power station was built. In 1932, a high concrete P. Dnieper hydroelectric power station was built (its maximum height is about 55 m). The spillway reservoir of the Nizhnesvirskaya hydroelectric power station is the first reservoir built on weak clay soils. In the 50s-70s. on high-water rivers were built: alluvial earthen P. on the Volga near Kuibyshev and Volgograd, concrete P. Bratsk hydroelectric power station on the Angara (height 128 m) and Krasnoyarsk hydroelectric power station on the Yenisei (124 m) ( rice. 1), a high 300-meter stone-earth P. Nurek hydroelectric power station on the river. Vakhsh, the arched Sayanskaya hydroelectric power station on the Yenisei (height 242 m, crest length 1070 m; currently under construction, 1975), and many others. The design and construction of hydroelectric power stations in the USSR are distinguished by a high technical level, which allowed Soviet dam construction to occupy one of the leading places in the world.

Of the P. built abroad, it should be noted: multi-arched P. Bartlett, height 87 m (USA, 1939), stone P. Paradela, height 112 m (Portugal, 1958), earthen P. Ser-Ponson, height 122 m ( France, 1960), stone-earth P. Miboro, height 131 m (Japan, 1961), gravity concrete P. Grand Dixence, height 284 m (Switzerland, 1961).

The type and design of a building are determined by its size, purpose, as well as natural conditions and the type of main building material. Based on their purpose, a distinction is made between reservoir reservoirs and water-lifting reservoirs (intended only for raising the level of the upper pool). Based on the magnitude of the pressure, pumps are conventionally divided into low-pressure (with a pressure of up to 10 m), medium-pressure (from 10 to 40 m), and high-pressure (more than 40 m).

Depending on the role performed as part of a waterworks, the water supply can be: deaf, if it serves only as a barrier to the flow of water; drainage, when it is intended to discharge excess water flows and is equipped with surface drainage holes (open or with gates) or deep drainages; station, if it has water intake openings (with appropriate equipment) and water conduits feeding hydroelectric power station turbines. Based on the main material from which dams are built, a distinction is made between earthen dams, stone dams, concrete dams, and wooden dams.

Earthen P. is constructed entirely or partially from low-permeability soil. Low-permeable soil laid along the upper slope of the P. forms a screen; When such soil is located inside the body of the soil, a core is created. The presence of a screen or core makes it possible to construct the rest of the pavement from permeable soil or from stone materials (stone-earth pavement). At the bottom of the lower slope of the earthen P., drainage is installed to drain water filtered through the body and base of the P. The upper slope of P. is protected from the effects of waves by concrete slabs or rock riprap. When constructing an earthen embankment, soil is extracted from a quarry using excavators, transported to the construction site by dump trucks, placed in the body of the structure, leveled with bulldozers, and compacted layer by layer with rollers. The construction of alluvial soil involves the development of soil by dredgers or hydraulic monitors, transportation of the pulp through pipes and its distribution over the surface of the constructed soil, after which the water drains away and the settling soil compacts itself. To prepare the foundation and construct an earthen pipeline in the river bed, its foundation pit is fenced off with lintels, and the river is diverted through pre-laid temporary conduits, which are closed after the construction of the pipeline.

In stone (fill-fill) paving, the screen or central waterproof element (diaphragm) is made of reinforced concrete, asphalt, wood, metal, and polymer materials. The requirement of low water permeability also applies to the base of the P. If the base soil is permeable to a great depth, it is covered in front of the P. with a drooping layer (for example, made of clay), forming one whole with the screen. P. with a core is complemented by a device at the base of a steel sheet pile wall or an anti-filtration curtain. The stone in rockfill and rock-earth paving is poured in layers of great height.

Concrete floors are usually classified according to their design, depending on the shear conditions; Accordingly, there are 3 main types of P. ( rice. 2) ≈ gravity dams, arch dams, buttress dams. Basic The material for modern concrete floors (mostly gravity-based) is hydraulic concrete. One of the most important issues in the construction of concrete substructures is the reduction of water filtration in the base. For this purpose, an anti-filtration curtain is installed at the base of a high concrete floor near the top edge. In the remaining section, the base is drained to reduce water pressure on the base of the floor, which increases the stability of the structure. To avoid the formation of cracks due to temperature fluctuations, gravity and buttress panels are cut lengthwise into short sections, the seams between which are covered with waterproof seals (see Waterproofing). To prevent the appearance of cracks as a result of shrinkage of concrete during hardening and to reduce thermal stresses, the concrete block is concreted in separate blocks of limited sizes; artificial cooling of the components of the concrete mixture and the concrete laid in the blocks is used by circulating coolant (from the refrigeration unit) through a system of pipes laid in the body of the concrete block. Concrete pavement in the river bed is usually constructed in 2 stages under the protection of lintels enclosing the pits. During the construction of the first stage of the river, the river flows along the free part of the riverbed; in the second case, through the holes (holes) left in the P., which are closed upon completion of all construction work. If the river bed is narrow, a concrete waterway is built in one step, with the river temporarily diverted into coastal waterways. A low-pressure concrete spillway dam, common in the practice of hydraulic engineering, built on a non-rock foundation and designed to pass large flows of water, has the design shown in rice. 3. Its basis is made up of drainage spans formed by concrete flutbet and bulls and blocked by hydraulic gates. Behind the spillways, a massive channel support is installed - a water trough (sometimes buried in the form of a water well), followed by a lighter fastening - an apron. Drainage is installed under the reservoir. The spillway is connected to the shores or earthen P. by massive abutments. A low-pressure concrete spillway is usually built using reinforcement, often the entire structure (see Reinforced concrete dam). In order to save material, flutbet and bulls of this kind are sometimes made of a lightweight cellular structure, with the cells filled with soil.

In forest areas, low-pressure wooden pumps of pile and cord construction are often built (usually they are equipped with spillways).

A special type of water-retaining structure is a collapsible navigable bridge. To erect it during summer low water, buttresses made of steel trusses are installed on a flat surface, bridges are laid across them, on which gates of the simplest design rest. The port supports the level of the upper pool, and ships and rafts go through the lock. During high-water periods, gates and bridges are removed, buttress trusses are laid on the flatbet, opening the way for ships and rafts through the P.

The general trend of modern dam construction is to increase the height of the dam. Technically achieved heights can be exceeded, but from an economic point of view, the construction of two successive dams of lower height often turns out to be more rational than one high one. Improvement of types of construction made from soil materials is carried out while simultaneously reducing the cost and speeding up their construction by increasing the power of construction mechanisms and vehicles. Increasing the efficiency of concrete floors is achieved by reducing their volume, replacing gravitational floors with buttresses, and the wider use of arched floors. This trend is accompanied by an improvement and specialization of the properties of cement and concrete. It is very effective to combine a spillway dam and a hydroelectric power station building in one structure, which ensures a reduction in the concrete (most expensive) part of the pressure front of the hydroelectric complex. This problem is solved both by placing hydraulic units in a high-pressure cavity and by using an underwater array of a low-pressure hydroelectric power station to install spillway openings in it.

Lit.: Grishin M. M., Hydraulic structures, M., 1968; Nichiporovich A. A., Dams from local materials, M., 1973; Moiseev S.N., Rock-earth and rock-fill dams, M., 1970; Grishin M. M., Rozanov N. P., Concrete dams, M., 1975; Production of hydraulic engineering works, M., 1970.

A. L. Mozhevitinov.

Wikipedia

Dam

Dam- a hydraulic structure that blocks a watercourse to raise the water level, also serves to concentrate pressure at the location of the structure and create a reservoir.

Dam (Karelia)

Dam- a rural settlement in the Loukhsky district of the Republic of Karelia, the administrative center of the Plotinskoye rural settlement.

Dam (Yaroslavl region)

Dam- a village in the Gavrilov-Yamsky district of the Yaroslavl region. It is part of the Velikoselsky rural settlement, being the center of the Plotinsky rural district and the Kolos collective farm.

Located near the Yaroslavl - Ivanovo highway. It borders the village of Shalava. Adjacent to Sidelnitsy and Vostritsevo. It has a store that serves the residents of the above villages, and an asphalt road.

Dam (disambiguation)

Dam:

• Dam- a hydraulic structure that blocks a watercourse or reservoir to raise the water level.
• Dam- natural limestone formation of karst caves.
• Dam- names of a number of settlements:
  • Dam - village in Karelia
  • Dam - a village in the Kostroma region
  • Dam - a village in the Perm region
  • Dam - a village in the Rostov region
  • Dam - a village in the Sverdlovsk region
  • Dam - a village in the Tyumen region
  • Dam - a village in the Yaroslavl region
  • Dam - a village in the Lugansk region of Ukraine
• Pompeia Plotina (d. 121/122) - wife of the Roman emperor Trajan.

Dam (Lugansk region)

Dam- village, belongs to the Stanichno-Lugansk district of the Lugansk region of Ukraine.

The population according to the 2001 census was 764 people. Postal code - 93643. Telephone code - 6472. Covers an area of ​​3.71 km².

Dam (Sverdlovsk region)

Dam- a village located in the Nevyansky urban district of the Sverdlovsk region (Russia) north of Yekaterinburg, south of Nizhny Tagil and 28 km south of the regional center of the city of Nevyansk near the dam on the Ayat River, propping up Lake Ayat. The nearest settlements are Shaidurikha, Pyankovo, Kunara.

According to historical data, the Dam does not appear in the lists of settlements of the late 19th century.

Examples of the use of the word dam in literature.

Now he pulled this rope, and a howling pack of hounds burst out and mingled with the maddened bulls and sheep, among whom eight excisemen were panickingly trying to make their way back to dam.

By dam a man was walking quickly - Alexandrinsky and Lidochka, busy in conversation, saw him when he came very close.

In the hive of the Great White Brotherhood, Hermes Trismegistus was formed, whose influence on the Italian Renaissance was irrefutable, as well as on the Gnosticism of Princeton, Homer, the Gallic Druids, Solomon, Solon, Pythagoras, Plotinus, Joseph of Arimathea, Alcuin, King Dagobert, Saint Thomas, Bacon, Shakespeare, Spinoza, Jacob Boehme, Debussy, Einstein.

From Amina, Salavat learned why everyone listened to him so much and stood up for him before the foreman: he learned that the workers he dispersed never returned to the site of the destroyed construction site and did not begin to dams.

And here are the arches of the railway bridge across the Volkhov, the stormy white foamy waters of which, pouring over dam, rushing under the bridge.

When all the wells were filled with water, the beaver team immediately dismantled dam so that no one understands where the water came from.

Shortly after noon the river became narrow and shallow, and then the path was blocked by a giant dam beavers, the air was filled with the menacing slip of beaver tails and the gloomy hum of the turuins.

In 1898, in Transbaikalia, on the Bodaibo River, in the area of ​​​​the rich Zakharyevsky mine, bottom ice that surfaced and clogged the entire channel formed dam, around which a large ice then appeared.

But, raising the countercurrent, Her to dam The wave carried her out, And there she remained by the shore, Where Flanders competed with Brabant at the bowling pins.

There was a feeling of unprecedented lightness and freedom, dam collapsed, it turned out that any gurgling and quacking can be pasted into the music.

On dam The barge haulers mixed into a solid mass, through which one had to make his way with great effort, and Osip Ivanovich again turned to the help of the most selective curses, the choice of which he had a remarkably varied choice and amazed even the barge haulers.

Remained powerful in my memory dam hydroelectric power stations with waterfalls overflowing the shields, we were just driving in a small truck along the lower pool, and it seemed that the water was bubbling and collapsing on us, and the wind was blowing splashes and foam onto the road.

He was by nature an excellent horseman and marksman with a bow, crossbow and gun; he often went hunting alone to the distant ridge of foothills, where the water of Bris rushed madly in a white stream through dams and tailwaters of the ancient canal system.

But what was the amazement of the engineer and his companions when they saw that the shipyard was destroyed, the trench was partly filled up, the drainage was blocked by sand dam and that, therefore, it is in no way possible to let water into Melrir before thorough corrections are made in this point!

Atlantic Wall, began restoration work on dams Mene and Eder.

Classification. In SNiP II-54-77; Concrete and reinforced concrete dams are divided into the following main types according to their design.

Gravitational (Fig. 7.1, a-6): massive (Fig. 7.1, a); with extended seams (Fig. 7.1,6); with a longitudinal cavity at the base (Fig. 7.1, c); with a screen on the pressure side (Fig. 7.1, d); with anchors in the base (Fig. 7.1,6).

A gravity dam is a massive structure whose stability is ensured mainly by the mass of the structure.

Buttress (Fig. 7.1, f-h) with massive heads (massive-buttress, Fig. 7.1, f); with an arched ceiling (multi-arched, Fig. 7.1, g); with a flat ceiling (Fig. 7.1, h).

These dams are a series of buttresses 5 (walls) located at some distance from each other with pressure ceilings in the form of massive caps 6, or arches 7, or flat slabs 8, etc. (domes, flexible ceilings).

Arched - at (Fig.7.1, m; b - width of the dam at the base, h - height of the dam); with pinched heels (Fig. 7.1,i); with a perimeter seam (Fig. 7.1, /с); from three-hinged belts (Fig. 7.1, l); with gravity abutments (Fig. 7.1, m).

Typically, arch-gravity dams are considered a type of arch dam (which is also accepted below in Chapter 7.4).

An arched dam is a spatial water-retaining structure in the form of a vault that transfers the loads acting on it mainly to the rocky shores of the gorge.

Often, so-called cellular dams are distinguished separately, having cavities usually filled with soil (Fig. 7.2, 7.3). They can be either gravitational (Fig. 7.2, a, b) or buttress (Fig. 7.2, c, 7.3), and in some cases they can be attributed to each of these types (Fig. 7.2, c).

Concrete and reinforced concrete dams, which differ in design from massive gravity dams (Fig. 7.1, a) and have a smaller volume of concrete than the latter, are often called lightweight (Fig. 7.1,6-m, 7.2, 7.3).

According to their technological purpose, dams can be either blind (Fig. 7.1, a-e, g, h) or spillway: with surface (overflow) holes (Fig. 7.1,6, f, 7.2, 7.3), with deep holes (Fig. 7.23, 6) and two-tier (Fig. 4.1, e).

General characteristics of the main types of dams. The dams under consideration are erected on various foundations - rocky, semi-rocky and non-rocky, while arched dams are built only on rocky ones. Concrete dams are usually built for rocky foundations, and reinforced concrete dams for non-rocky foundations. For non-rocky foundations, they are usually arranged as spillways; blind dams here usually turn out to be uneconomical, and the blind part of the pressure front of the hydroelectric complex is blocked by an earth dam.

Properly designed concrete and reinforced concrete dams of all types are seismic resistant, even at high seismicity (but in the absence of differential foundation movements). Concrete dams are successfully used in harsh climatic conditions and on high-water rivers; with sufficiently wide openings, they make it possible to do without tunnels while skipping construction costs; they are used at various pressures (heights), including large ones; volumes of concrete can reach several million cubic meters.

The disadvantage of dams in this group is the cost of their construction of concrete and metal, which are usually not local materials (require significant transportation costs) and can be scarce and relatively expensive under certain conditions.

For reliable design and construction of the dams under consideration, it is extremely important to know and correctly assess the geological conditions at the site of construction of the hydroelectric complex; obtain reliable geotechnical characteristics of soils (especially shear and deformation characteristics, including for fillers of cracks in rocks).

Great advances in the development of soil mechanics (including rock mechanics) and methods for improving foundations in recent years have contributed to the improvement and reliable use of concrete and reinforced concrete dams, including at high pressures and on non-rocky foundations. The largest and most outstanding dams in terms of engineering on non-rock foundations were built in the USSR (on the rivers Svir, Volga, etc.)

There are two ways to reduce the cost of concrete dams.

1. Simplification of the structure (refusal to install various water conduits, holes in it or reduce them to a minimum; use of a simple massive gravitational structure, reducing the amount of formwork, etc.). This makes it possible to build them using high-performance methods, widely using mechanization (layer-by-layer laying of low long blocks of concrete using the Toktogul method, the use of conveyors, etc.); do not monolith construction seams (or not monolith all seams); use low-cement rollable concrete mixtures,

During the construction of the Willow Creek gravity dam (USA, 1982, A = 66.5 m, volume of concrete 306 thousand m3) from a compacted concrete mixture, the cement consumption at the top edge was 104 kg per 1 m3 of concrete, and in the inner zone 47 kg /m3 with the addition of fly ash 19 kg/m3.

Rolling was carried out using vibrating rollers in layers 25...30 mm thick in four passes of the roller; the cost of rolled concrete was 3.4 times less than the cost of conventional massive concrete. The time and cost of construction were significantly reduced compared to the option of a hydroelectric complex with a rock-earth dam. 2. Lightening the structure - reducing the volume of concrete through the use of buttresses and cellular structures, taking into account spatial considerations!” work of the structure (arch dams, gravity dams with embedded intersectional joints, etc.), anchoring (involvement of the base in the work), etc.

In each specific case, it is necessary to analyze which of these directions is the most rational. At the same time, a combination of these directions is promising and may be appropriate - reasonable lightweighting of the structure (not leading to significant production complications) and its construction using high-performance industrial methods developed or modified in relation to this design. For example, the design of the lightweight (massive buttress) Kirov dam (L = 83 m) was adopted in such a way (sufficiently thick buttresses, etc.) that it could be successfully erected by layer-by-layer concrete laying.

With a rock foundation, lightweight gravity dams (Fig. 7.1,6-d) compared to massive gravity dams (Fig. 7.1, a) have a volume of concrete less by about 8...15% (rarely more than 15%). Anchored dams at low heights (up to 20 or 30 m) can also provide greater savings in concrete (Ault na Lairridge dam, h = 22.2 m - 50%). The use of massive buttress dams allows for concrete savings of up to 25...40% (Fig. 7.1,e), dams with flat pressure ceilings - 25...45% (Fig. 7.1,6), multi-arch dams -30... 60% or more (Fig. 7.1g). In favorable geological and topographic conditions with relatively narrow sections, the volume of concrete of arch dams (Fig. 7.1, and m) is reduced by 50...80% or more compared to the volume of concrete of a massive gravity dam under similar conditions. For arch-gravity dams this reduction is significantly less (about 20...30%).

In terms of cost, the percentage of savings is less (by 5...10%, sometimes more) due to complications in the work, a slight increase in concrete grades and an increase in formwork work for lightweight dams, etc. It depends on many local conditions - the method of passing and the values ​​of construction expenses, cost of labor and materials, etc.

With a non-rock foundation, significant savings in concrete (up to 20... 45%) compared to a massive structure (see Fig. 7.25) can usually be obtained only when loading cavities with ballast, that is, when using various cellular structures with filled cavities (Fig. 7.2 , 7.3). This is due to the fact that with a solid foundation slab (Fig. 7.2,6), which is usually required for a lightweight dam with a non-rock foundation (except for the design of A. M. Senkov, Fig. 7.2, a), the filtration pressure does not decrease compared to a massive gravity dam (with lightweight dams on the rock, shown in Fig. 7.1,6c, and buttress dams, it decreases), and a significant flattening of the pressure face of the buttress dam, necessary from the condition of ensuring the stability of the dam for shear in the absence of soil loading of the cavities between the buttresses, is almost always leads to an insufficiently constructive solution.

Massive gravity dams on rock foundations (Fig. 7.1, a) have become widespread due to their simplicity. Dams with expanded seams (Fig. 7.1,6) were successfully used in a number of cases, but were not widely used; dams with a longitudinal cavity (Fig. 7.1, a) have found use only in isolated cases. This can be explained by the fact that the savings in concrete with these types of lightweight dams are not very large, but the work on their construction becomes somewhat more complicated. Dams with a screen on the pressure face are still rarely built, but recently attention has been paid to them, and a number of interesting studies and studies have been carried out in relation to the Kurpsai dam (a version of this dam without a screen has been adopted). In such a design, with reliable operation of the screen, it is possible to allow tensile stresses on the top edge (which gives a more compressed profile) and lower the requirements for the grade of concrete (remove the requirement for water resistance, allow the formation of cracks at the top edge). Their use is hampered by very high requirements for the quality of the screen (made of stainless steel or polymer materials) and doubts about the possibility of reliably meeting these requirements, as well as the complexity of repair work in the event of damage to the integrity of the screen.

Anchored dams (Fig. 7.1, c?) are used in a number of cases, and they are made as gravity and as buttress dams at heights usually not exceeding 55...60 m (at higher heights, difficulties arise in creating the pre-tensioning required to obtain the proper effect anchors), on good rock foundations, which allowed for reliable anchoring.

Anchoring was also used in the superstructure of dams. Such dams have not become widespread, mainly due to some complexity in the implementation of this design, difficulties in placing various culverts in the dam in the presence of anchors, and rather high requirements for the foundation and the quality of the anchoring.

Of the various types of buttress dams, especially over the last 30...40 years, the most widespread are massive buttress dams (Fig. 7.1, e), which have fairly thick elements and small reinforcement (5...15 kg of steel per 1 m3 of concrete and less), which makes it possible to build them using industrial methods and use them in harsh climatic conditions. Multi-arch dams are used much less frequently, which is explained by the complexity of their construction and large reinforcement (30... 50 kg of steel or more per 1 m3 of concrete). Dams with flat pressure ceilings are now very rarely built. Of the relatively new dams of this type, only the Mada dam in Malaysia, built in 1970, and the Cordova dam in the USA can be mentioned (h = 27.4 m, spans between the axes of the buttresses 12.5 m). This is due to the fact that the structures of such dams are relatively thin-walled (which is not always acceptable under the conditions of modern work), and covering significant spans with slabs is usually impractical. In addition, quite significant reinforcement of the structure is required (20...40 kg of steel per 1 m3 of concrete or more). The relative thinness of the elements can sometimes be undesirable for durability reasons.

The significantly greater prevalence of massive buttress dams compared to similar gravity dams with expanded seams is quite natural, since they provide greater savings in concrete (see above) without significant additional complication of the design. Buttress dams, in addition, make it possible to obtain large (in modulus) vertical compressive stresses a" at the base at the pressure face (Fig. 7.4, a, b) and thereby prevent the opening of the contact seam at the base in the area of ​​the grouting curtain. With buttress dams, if necessary, it is possible to obtain a fairly uniform stress diagram in the foundation, which is one of their advantages and has been implemented in a number of dams, especially on relatively low-modulus foundations. This can be achieved by constructing a flatter bottom edge in the lower part of the buttress (tide A in Fig. 7.4, c), and if additional stress reduction is necessary, by constructing a full or partial foundation slab (Andijan dam - see Fig. 7.44, Ben Metir).

In the body of buttress dams, stresses are distributed more evenly than in massive gravity dams.

This disadvantage of massive gravity dams (small ohm in the contact seam) can be eliminated or reduced by using anchoring (Fig. 7.1, e, 7.4, d), constructing a longitudinal cavity (Fig. 7.1, c), using appropriate cutting of the dam, temporary, grouted before filling reservoirs using a seam (Fig. 7.4, e), as well as using an “active seam” with flat jacks (Fig. 7.4, f). The last effective measure has been applied in practice only for buttress dams; it involves the base in the work and allows you to reduce the volume of concrete with a favorable distribution of stresses in the base. Active joints with flat jacks are simple and have proven themselves in practice.

A fundamentally different solution, taking into account the possibility of opening a contact seam in a gravity dam in the case of small calculated values ​​of oy, which in reality may turn out to be tensile (especially with a compressed profile), is the construction of a short depression with a grouting curtain under it, somewhat placed in the VB beyond the zone of possible the occurrence of tensile stresses (see Fig. 7.1, d). With this solution, the seals in the seam between the short depression (or the mass above the curtain) and the body of the dam are very important, the repair of which is difficult. This solution can be considered necessary when tensile stresses are allowed on the upstream face of the dam. It is permitted by SNiP II-54-77 only if the top edge is waterproofed (see Fig. 7.1, d). It should be considered in case of unfavorable multi-modulus foundation, when under the lower part of the dam it has a lower deformation modulus than under the upper part.

Arch dams have become widespread in mountainous areas in many countries around the world and

have proven themselves well in operation. They are usually economical, fit well into the surrounding landscape, are beautiful, and work reliably in conditions of high seismicity and overloads. Thus, the Pacoima dam with a height of 116 m (California, USA) withstood a very strong earthquake with a maximum horizontal acceleration of 1.25 g and a vertical acceleration of up to 0.75 g without damage, and the Italian thin Vajont dam with a height of 266 m and a thickness at the bottom of 23 m survived, receiving very slight damage when a wave about 70 m high overflowed through it in 1963, caused by a huge landslide in the reservoir, into which about 300 million m3 of rock fell in 5...7 minutes.

The most common are arched dams with pinched heels (Fig. 7.1, i), as well as with a perimeter (contour) seam (Fig. 7.1, c); dams with abutments are also often built (Fig. 7.1, l). Dams that are more complex in construction, divided by seams into separate arches (including those from three-hinged belts - Fig. 7.1, l), working mainly as flat systems, are erected only in isolated cases at low heights.

Recently, arched dams of the dome type have become widespread, that is, with significantly curved vertical sections (the so-called consoles). In such dams it is usually possible to obtain the most favorable stress distribution.

Arch-gravity dams are currently used mainly at high pressures, in fairly wide sections and when culverts - spillways, hydraulic station pipelines (Sayano-Shushenskaya, Glen Canyon dams) are located in the dam body.

Concrete and reinforced concrete dams are usually built from cast-in-place concrete. Only in isolated cases and at relatively low heights were such dams made entirely from prefabricated elements (the multi-arch Mefrush dam in Algeria with a height of 25 m, the experimental cellular dam on the Stepnoy Zay River in the USSR and some others). This is mainly due to the fact that such dams are not mass standard structures and prefabricated non-standard structures are in most cases ineffective even for small and moderate heights of structures.

At low pressures (5...7 m), in a number of cases prefabricated monolithic cellular structures were used, consisting of blocks in the form of paired reinforced concrete slabs, monolithic with concrete (Fig. 7.2,6). Four dams of this type were built according to Giproselelectro projects (Krasnoyarsk on the Medveditsa River, Perevozskaya, Lykovskaya and Shilskaya). A similar type of dam was built in Iraq (Soyuzgiprovodkhoz project).

Separate prefabricated elements that facilitate the work (grooved structures, parapets, slabs of reinforced concrete permanent formwork for buttress dams, permanent reinforced concrete formwork for viewing galleries, etc.) are used in the construction of concrete and reinforced concrete dams.

Gravity, buttress and arch dams can be made not only from concrete, but also from masonry with mortar. Currently, masonry dams have practically been replaced by concrete ones, which have significant production advantages (the possibility of extensive mechanization, high rates of work, etc.). Only in India are gravity dams still sometimes built from masonry. In 1969, the construction of the 124.7 m high Nagarjanasagar rock dam, the tallest dam of its type in the world, was completed there.