Fundamentals of hydropower. Types of dams

Man is not just a child of nature. He's trying to change environment around you, making it more comfortable to live in. This makes him different from animals. For a long time, people have tried to curb the elements so as not to depend on the vagaries of nature and weather. So, they learned to build dams so that there would always be water for irrigating fields and watering animals. This engineering device helps people conserve and rationally use both water and land resources, and also prevents devastating floods.

What is a dam?

A dam is a barrier that holds back or controls the flow of water. Thanks to them, artificial reservoirs are created in which life-giving liquid is accumulated and then consumed as needed.

In addition to storage functions, a dam on a river can bring even greater benefits when the power of the water flow powers power plants that supply cities and towns. settlements electricity. Over the years, people have learned not only to control rivers, but also to force them to work for the benefit of the country.

Complex structure

A dam is a hydraulic structure with various functions. During the construction of each new structure, preliminary work is carried out, as a result of which an economic justification is made and the technical capabilities of the future structure are calculated. The construction of a dam is a complex and labor-intensive process that requires highly qualified workers both at the design stage and during its construction and further operation.

Types of dams

A dam is a structure that is not built according to a single model. Each specific object requires its own parameters and calculations. There are several types of dams.

Solid reinforced concrete has an almost unlimited safety margin. This material is capable of holding back powerful flows of water. They are also called gravity because they are held on the surface of the earth due to the force of gravity, firmly fixing the reinforced concrete in place. These dams are very expensive because they consist entirely of the specified material. Therefore, they are built only on the most powerful rivers and are used for a very long time.

Dams made of hollow reinforced concrete are much cheaper than solid ones. Their insides are reinforced with steel reinforcement of various sections to increase the safety factor.

Earthen ones are built from soil, stones, sand to hold back the flow of water. They are often erected in areas of river floods as temporary barriers around populated areas.

Another type of dam is levees and embankments, which are designed to prevent flooding if river levels rise. The height of the dam depends on its technical characteristics. Earthen ones are rarely poured higher than 15 meters, but reinforced concrete ones can be of almost any height required by the project.

Historical facts

Dams are structures that have been built since ancient times. The oldest known is over 4,500 years old and was discovered in Egypt.

But one of the world's largest hydraulic structures - the Hoover Dam on the Colorado River - was built back in 1930 in the USA and is still in use. Its length is 379 m with a height of 221 m. Dam workers claim that the layer of reinforced concrete here is so thick that in the central part it still, after almost 90 years, has not yet hardened. Thanks to this structure, the largest artificial lake in the world arose - Lake Mead, which supplies water to several arid states.

A dam is a peaceful structure. But there have been cases in history when such objects were used for military purposes. Often, during the siege of a city, invaders blocked the riverbed with an earthen dam, changing the direction of the water flow. The besieged inhabitants, exhausted from thirst, opened the gates. There were also opposite situations, when a rebellious town was flooded with the help of a dam. Many such structures were blown up during World War II so that the Nazis could not penetrate deep into the country.

By the way, according to one version of historians, the unfound grave of Genghis Khan also rests at the bottom of the river, which is why its search took so long. The construction of dams is a technique that this powerful conqueror often used.

Modern dams often perform three functions at once - they protect against floods, allow the accumulation of water reserves and help produce electricity.

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-Garawi.

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 Russian Empire There were already more than 200 objects, 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 may 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 soldiers from the Ministry of Emergency Situations 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 short term 62 dams were broken. 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.

Dam was the first hydraulic structure that ancient man learned to build. The dams of antiquity, of course, could not boast of height and grace, but were built from scrap materials. The function of such a dam was to retain water so that it could later be used for irrigation or as drinking water.

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Modern dam is a complex hydraulic structure designed to hold the required volume of water within specified limits. The most common use of a dam is to block a river bed to create pressure and reservoir for a hydroelectric power plant. In addition to generating electricity at hydroelectric power stations, rising water levels in the river create favorable conditions for timber rafting, navigation, irrigation and water supply. At the same time, when creating a reservoir, a significant area of ​​often fertile land is flooded, the natural migration of fish is hampered, and the climate near the reservoir changes.

Dams are classified according to several criteria:
By role in the waterworks:

• deaf;
• spillways;
• station;

By pressure value:

• low pressure;
• medium pressure;
• high-pressure;

According to the material used:

• concrete (reinforced concrete);
• ground;
• wooden;

By design:

• gravitational;
• buttresses;
• arched;

A dam is called blind if its design does not provide for spillway devices. spillway dam, as the name implies, is equipped with one of the types of spillway devices and is designed to pass an excess volume of water into the tailwater. Station Dam equipped with water supply devices.

The division of dams by pressure, as in the case of hydroelectric power plants, is conditional. Here are the most common values:

• low-pressure dams – up to 20 m;
• medium-pressure dams – from 20 to 80 m;
• high-pressure dams - from 80 to 200 m;

Side by side with the head criterion goes the dam material used. High-pressure dams are built from concrete or reinforced concrete; in the range of medium pressures, soil materials can be used for construction, and low-pressure dams can be built from wood.

In turn, its design feature is closely related to the material from which the dam is built. Earth dams And wooden dams can only be gravitational. This means the stability of the dam, that is, the ability to withstand the pressure of water from the reservoir, is determined only by its weight. Gravity dams can be erected on any foundation.
Reinforced concrete and concrete dams can be gravity, arched or buttressed.

Arch dam provides stability in a reservoir by transferring water pressure from the front of the dam to the banks or bank abutments. Its unusual design allows this to be done - a convex arc towards the upper pool, resembling an arch from above (hence the name). But because of this same feature, it can only be built on a rocky foundation.

Buttress dam It consists of concrete floors or vaults (arches) supported by buttresses. In this case, the pressure ceiling, in the form of slabs or vaults, does not stand vertically, but at a certain angle to the upstream. This design ensures stability not only due to the weight of the dam, but also due to the pressure of water on its inclined surface. The construction of a buttress dam is only possible on a rocky foundation.

Of all the dams, arch dams certainly make the greatest impression. It seems absolutely incredible how a thin curved concrete wall can hold billions of tons of water, and at the same time have a huge margin of safety. Well, in the end, arched dams are simply very beautiful.

Xiaowan is the highest arch dam in the world. Photo from here

The operating principle of arch dams is fundamentally different from all other types of dams. If gravity and buttress dams put pressure on the base, then arch dams transfer the load to the banks. An arched dam can even be specially cut off from the base using a special cut seam (this is sometimes done to relieve the stresses that arise in some types of dams).

Lumei Dam with a seam at the base

At the same time, the concrete in the arch dam works under compression, and in such a situation its strength is extremely high. Accordingly, an arch dam can be surprisingly thin - at a height of a hundred meters, its thickness can be only 2-3 m.

At the same time, such thin arched dams are not always built. Depending on specific conditions, it may be more effective to build a thicker or even an arch-gravity dam, the stability of which is ensured by both the emphasis on the banks and its own weight.

The main advantage of a concrete dam is significant savings in concrete, reaching 80% of the amount of concrete in a gravity dam. At the same time, arch dams place special demands on the banks - on the width of the valley, its shape and the quality of the rocks.

Inguri Dam. Photo from here

In wide valleys, the construction of arch dams is ineffective. There is a special coefficient that reflects the ratio of the length of the arched dam along the crest to its height (L/H). The most effective construction of arch dams is if this coefficient does not exceed 3.5, although there are known cases of construction of arch dams in relatively wide sections - for example, for the Sayano-Shushenskaya hydroelectric power station L/H = 4.56, for the Pieve di Cadore dam in Italy L/H=7.45.

Pieve di Cadore Dam. Photo from here

They do not like arched dams and asymmetrical valleys - the arch does not work normally in them. If necessary, they even resort to the construction of special tie-ins and retaining walls. And finally, the rocks into which the arch dam rests must be very strong. Accordingly, the ideal place for an arch dam is a mountain gorge, where they are mainly built.

Scheme of the Xiaowan hydroelectric dam.

The stability of arch dams is extremely high. In model experiments, they were destroyed only under loads 3-5 times higher than the calculated ones. There is a well-known example of a disaster at the Vayont dam (very high and very thin), when a landslide in the reservoir caused an overflow of water over the dam in a layer of at least 70 m - the dam stood and, moreover, was almost not damaged.

Vayont Dam. Photo from here

There are few arch dams in Russia - three purely arch dams (Chirkeyskaya, Miatlinskaya and Gunibskaya) and two arch-gravity dams (Sayano-Shushenskaya and Gergebilskaya). There is a project for the Agvalinskaya hydroelectric power station on the Andiiskoye Koisu River with an arch dam 210 m high.

Chirkey hydroelectric power station. Photo from here

The highest arch dam in the world is the dam of the Chinese Xiaowan hydroelectric power station on the Mekong River with a height of 292 m, commissioned in 2010. Before that, for a long time the leadership was held by the Inguri hydroelectric power station dam in Georgia, its height is 271.5 m. Many high-rise arch dams are being built in China - for example, the Xiluodu hydroelectric power station dam is 278 m high (by the way, the power of the hydroelectric power station is also impressive - 13,860 MW!). The highest arch dam in the world is also being built there - Zhinpin-1 with a height of 305 m. However, this is not the limit - there is a beautiful project for the Abu Sheneila Dam in Sudan with a height of 335 m!

Contents of the article

DAM, a massive lintel erected to retain water flow, the main hydraulic structure for use and regulation water resources. Already in prehistoric times, in Egypt, Mesopotamia and other areas of human habitation, simple dams were built in the form of embankments of earth and stones. For many centuries, the design of dams was determined by considerations drawn only from practical experience, and only in 1853 the French engineer De Sasilli theoretically substantiated their design principles.

Spillway dams are built to raise the water level of a river or to divert water flow, which is usually necessary during the construction of power plants, for navigation or for irrigation of land. Blind dams (without the passage of water) block a watercourse and create reservoirs intended to provide cities with water or electricity, or for irrigation purposes, etc. In many dams of this type, the upper part is arranged so that, if necessary, it can serve as a spillway. The dam resists the pressure of water either by its own weight (gravity dams) or by its design, the power elements of which ensure the stability of the entire structure (arched, buttress dams). Gravity dams are made in the form of masonry, concrete barriers, earthen or rock (crushed stone) filler; other dams are built from concrete, reinforced concrete, steel structures, or timber.

Shear forces.

The dam is subject to various shear forces caused by the pressure of water, ice, sediment, wind, wave impacts, gravitational forces, temperature changes, and soil reaction. In some areas it is necessary to take into account the possibility of earthquakes. Underestimation of any forces can lead to the destruction of the dam due to displacement of its base or overloading of its structural components.

The horizontal component of water pressure increases with depth, being equal to the product wh, Where h– depth and w– weight per unit volume of water. Consequently, the total hydrostatic pressure on a unit length element of the cross section of the dam body is 1/2 ( wh 2), and the resultant of its vertical distribution is applied at the level of a third of the dam height. When calculating the water pressure on a dam, the most difficult thing to determine is the filtration pressure acting on the base of the structure due to the fact that water seeps under it. To find out the order of magnitude of such forces, numerous studies are carried out both on dam models and in natural conditions. The values ​​of these forces vary depending on the ability of the soil bed to pass water. If the dam foundation cushion is pebbles, river sand, porous rock or any loose sediment, then the pressure on the base of the dam's support prism will be equal to the full hydrostatic head. When the base of the dam is fastened with cement mortar to monolithic rock soil and the mortar fills all its cracks, then this pressure constitutes a relatively small fraction (10–40%) of the hydrostatic head. Its decrease along the base of the dam from the upstream support prism to the downstream one depends on the distance and shear forces, and at the edge of the downstream slope of the dam the pressure in the downstream becomes less. The area of ​​the dam base, which is subject to filtration pressure, varies from its full value (for dams on sandy and pebble soil) to 0 (for dams with a solid concrete slab on rocky soil). To reduce the influence of filtration pressure, drainage and bypass paths are made for water flows that can penetrate under the dam.

The main effect of waves on a dam is manifested in periodic changes in the depth of the water mass in contact with the dam, although under some circumstances the pressure face of the dam may also experience powerful shocks from waves due to their kinetic energy. A good approximation to reality is given by Hoxley's formula () for the dependence of wave height h from length L its “surge” (in meters), i.e. the distance at which the wave reaches its full height. The ice pressure on the dam is not determined entirely accurately, but it is still much less than the forces that arise due to the increase in the volume of the reservoir in front of the dam. A practically acceptable estimate of ice pressure is on average 210 kg/m2. The pressure from ice masses can be reduced by blowing air through perforated pipes laid in front of the dam at great depths. Air bubbles, rising upward, drive warmer water to the surface, and it prevents the formation of ice.

Gravity dams.

A gravity dam is insured against collapse if the resultant of all pressure and gravity forces acting on it is applied to the base of the structure; however, a dam of flawless design requires that this resultant be applied to the base of the core located in the middle part of the dam body. The compressive stresses developing in the downstream and upstream support prisms of the dam can be calculated from the formula V/b(1 ± 6 e/b), Where V– vertical component of the ground reaction force, e– removal of the point of its application from the center, b– width of the dam base; The plus sign in brackets is taken for the lower prism, and the minus sign for the upper one. If the point of application of the resulting force goes beyond the boundaries of the middle third of the base of the dam prism, but is still located within the base itself, then the stress on the bottom prism is determined by formula 2 V/(b/2 – e). In this case, the permissible stresses should be less than the destructive stresses. The shift of the dam is prevented mainly by its friction along the soil bed, equal to the product V H f, Where f– friction coefficient. The shear resistance of the dam is provided additionally by deepening the protrusions of its base (teeth) into the ground.

Gravity dams are usually arcs in plan, supported by steep and solid river banks; Such structures have the properties of arches. The distribution of resistance to displacement of such a dam, which is generally proportional to the mass and other physical and mechanical characteristics of the material from which it is built, cannot be described by an exact formula.

Leaks.

Most often, water seeps behind a stone dam through the underlying soil layer. If a dam is placed on a layer of permeable rock, then usually its diaphragm is buried in the ground so as to completely block the path of seepage water or reduce its seepage to a minimum. They try to make the pressure face of the dam waterproof, but it is still advisable to provide for drainage of seeping water in the body of the dam in advance. Earthen dams are usually made with a concrete diaphragm, or the middle part of their thickness (core) is filled with denser soil. In rockfill dams, either waterproof diaphragms are built (from structures and dense natural materials), or their pressure faces are made of concrete, asphalt concrete or sheet steel.

When constructing dams made of monolithic concrete, it is necessary to take special measures to prevent the appearance of cracks through which water can leak. The fact is that when mixing a mixture of cement with sand and gravel or rubble stone in water, a chemical reaction develops in the resulting mass of liquid concrete with the release of heat and an increase in temperature, and then, when hardening, the concrete cools unevenly and shrinkage occurs, during which Shrinkage cavities and cracks may form there. The harmful effects of heating and shrinkage of concrete, which can lead to the formation of cavities and cracks, can be reduced by controlling the mixing process in various ways: use cement with low exotherm; reduce the proportion of cement to an acceptable minimum; pre-cool the solution before laying it so that the concrete block being created is formed at a lower temperature; Cool the kneaded mass using water or some other cooling system. Typically, the width of the formed monolithic block should not exceed 15 m, the thickness of the concrete mortar layer laid at one time is 1.5–3 m. The next layer or adjacent block can be laid after some time or with a corresponding decrease in the temperature of the already laid mortar. The joints of adjacent blocks are covered with waterproofing barriers made of rubber, plastic or non-corrosive metal. Nevertheless, measures are provided for the free flow of water from the inside of the waterproofing.

Arch dams.

An arched dam in the form of a single arc that blocks the river flow from one bank to the other is distinguished by the strength advantages of its design. It withstands water pressure thanks to three important properties that together ensure its stability: 1) the resistance of the vertical elements of its structure (which act as cantilevers embedded in the base); 2) mass; 3) the features of the arched structure, which rests its ends on the coastal abutments and transmits the water pressure through them. If the river valley is relatively narrow, then the arch itself bears the main load of the water mass; when the channel is wide, the other two properties also play a significant role. At the experimental Stevenson Creek dam, designed for a water level difference of 18 m, the supporting prism of the pressure face came off at a level difference of 6 m, but after that the arch withstood the full load. Given a suitable terrain, the construction of an arch dam is economically profitable, therefore in the 20th century. Quite a lot of such structures have been erected.

Loads.

The stresses experienced by the structural members of an arch dam are sometimes calculated by considering the dam as a segment of a circular cylinder with a distributed radial load. In this case, the form of the formula is quite simple: S = 41,9RH/T, Where S- voltage, R– radius of a circular cylinder, H– the height of the water column located above the level of the dam structural element under consideration, T– thickness of the dam arch at this level. The result is that the thickness should be constant at the same level and increase from the crest to the base of the dam. Since this does not take into account the stresses arising due to temperature changes, material shrinkage and shortening of the arch rib, the model of a simple cylinder needs to be clarified and, taking into account the dimensions of the dams, it is necessary to carry out calculations over the entire sequence of horizontal sections of the dam body, considering each of them like an elastic arch, its ends embedded in the coastal abutments. The calculation procedure is similar to that used in the design of arch bridges.

Since the cross-section of the river valley has a V-shaped profile, the arc of the crest of the arch dam is much longer than the arc of its base. If in calculations for horizontal sections from the crest to the base of the dam we take arcs of the same radius as a basis, then the curvature of the base of the dam will be insufficient, therefore some arched dams are calculated under the condition that the central angle is constant for all horizontal cross sections. However, this condition sometimes leads to non-smooth contours of the designed structure, so in practice, compromise approaches are usually found, using the constancy of either the radius or the central angle.

Multi-span dams.

Relatively low dams on rivers with a wide bed in a rock bed are often built from structural units in the form of continuous spans between supports, buttresses or trusses. The pressure floors that form the pressure face of the dam can be concrete cylindrical arches, reinforced concrete slabs, or structures of sheet steel or thick wooden planks. The angle of inclination of the pressure surface of the dam relative to the direction of the river flow is usually chosen to be close to 45°, therefore the component of the weight of the water acting on the dam helps to increase its stability.

A multi-arch dam is composed of concrete half-cylinders resting with their edges on buttresses located every 15 m. It is advantageous to make low dams on wide rivers with rocky soil from such multi-arch structures, since the arches work mainly in compression, which results in savings in materials during construction. The lower edges of the semi-cylinders are usually equipped with a concrete anchor tooth, buried in the rocky soil. In those places of the arches where tensile stresses may arise due to temperature fluctuations, steel reinforcement is introduced; in areas with cold climates, concrete arches should be made thicker to protect the reinforcement from low-temperature corrosion. Floors can also be made in the form of dome segments.

In dams with floors made of reinforced concrete slabs, the supports are triangular buttresses, and each slab is made so that it fills the span between adjacent supports and is connected to the tooth of the dam. In areas with cold climates, thin slabs are unsuitable for this type of dam, as they quickly lose their performance characteristics.

Few dams with pressure ceilings made of sheet steel were built; They are usually designed for low pressure. In a typical design of such a structure, sheets of steel, inclined at an angle of 45° to the flow, span relatively short spans of steel frames anchored in the rock. However, the sheet steel bends between the supports and experiences tension stresses rather than compression stresses (like an arch). To prevent water from seeping under the dam, sheets at the base of the structure are embedded in the tooth of the dam. Sheet steel is also used in the membranes of rock dams.