Chirkeyskaya HPP. Dagestan (photo report). The largest in the North Caucasus, the Chirkei hydroelectric power station is a unique dam among the rocks On which river is the Chirkei hydroelectric power station

I continue to rake tons of photo information from our Dagestan blog tour with RusHydro. And today we will talk about another pride of our hydro-construction idea, a unique hydroelectric power station located in fabulous places - about the Chirkeyskaya hydroelectric power station.

Chirkeyskaya HPP is located on the Sulak River near the village of Dubki, in the Buinaksky district of Dagestan. It is the largest hydroelectric power plant in the North Caucasus. It is included in the Sulak HPP cascade, being its upper stage that regulates the entire cascade. In addition, it is the main control station in the United Energy System of the South of Russia. Plus, in emergency situations, it is able to quickly replace the missing capacity of 150-300 MW thermal power plants. The dam of the Chirkeyskaya HPP is the second highest (232.5 m), after Sayano-Shushenskaya HPP(245 m) and the highest arched dam in Russia.

The installed capacity of the station is 1,000 MW, the provided capacity is 950 MW, average annual output electricity is 2,430 million kWh.

In 1928 - 1930, the Leningrad Department of Power Engineering carried out field surveys and design studies for the hydropower use of the Sulak River. The result of which was that the Chirkeyskaya hydroelectric power station would be in these places. Since 1931, the design of the station has been carried out by the Moscow branch of Glavgidroelektrostroy, which in 1933 prepared a draft design of a hydroelectric power station with an arched-gravity concrete dam, but it was rejected due to the need to continue exploration work in the section of the Chirkeiskaya hydroelectric power station due to difficult engineering and geological conditions.

1956 - 1960 returned to this problem, but the design of the station was already transferred to the Baku branch of Hydroproject. Two options for the layout of the hydroelectric power station were considered - with arched and earth dams. The first option was chosen and by the Resolution of the Council of Ministers of the USSR No. 570 dated June 8, 1962 it was approved.

2. View of the Sulak canyon from the crest of the dam. By the way, in its depth in this place (1,920 m) it significantly surpasses its famous brother the Colorado River Canyon (depth up to 1,800 m) in North America.

In practice, it turned out to be not so simple, so it was decided to transfer further patronage over the project to the Lenhydroproject Institute, which, having analyzed, made significant changes to the project, namely: geological conditions; design of a hydroelectric power station building with a two-row arrangement of hydraulic units, which made it possible to reduce the length of the building by half; changing the construction of the construction tunnel with an increase in its length from 350 m to 730 m, which made it possible to move it outside the unstable section of the slope.

December 14, 1967 technical project The Chirkeyskaya HPP was approved by the order of the Council of Ministers of the USSR No. 2881-P, but the go-ahead to start construction was given already on June 11, 1963 by the order of the USSR Ministry of Energy No. 84. for power supply of construction - power transmission line-35 kV from the Buinaksk substation and power transmission line-110 kV Chiryurt-Chirkey by the Construction Department “Chirkeigesstroy”. In August 1963, the development of the station construction site began, and in November 1964, the site was finally selected for the permanent settlement of Dubki hydropower.

3. General form for outdoor switchgear (open switchgear) - 330 kV, control building with an observation deck and an elevator shaft.

On October 29, 1967, the Sulak River was closed, and on February 28, 1970, the first concrete was laid in the foundation of the dam (onshore plug openings). Work, as always at that time, proceeded according to the Stakhanov style, record after record, and already on August 13, 1974, the dam of the Chirkei hydroelectric power station was put under pressure. On August 7, 1974, filling of the Chirkei reservoir began.

The first hydroelectric unit of the Chirkeyskaya HPP was launched on December 22, 1974, at an intermediate level of the reservoir and a dam erected to a height of 185 m.The second and third hydroelectric units were launched on September 28 and December 30, 1975, respectively. The last, fourth hydroelectric unit was put into operation on June 30, 1976.

Officially, the construction of the Chirkeyskaya HPP was completed on February 9, 1981 with the signing of an act of acceptance of the hydroelectric complex into commercial operation. During the construction of the Chirkeyskaya HPP, 2.686 million m³ of earth and rock works were carried out (including 2.143 million m³ of rock excavation), 1.491 million m³ of concrete and reinforced concrete were laid, 9.8 thousand tons of metal structures and mechanisms were installed.

4. By the way, we won't see such beauty soon. According to the plan of the RusHydro modernization program, the local 330 kV outdoor switchgear will be replaced with a modern 330 kV switchgear (SF6 switchgear)

The structure of the station includes an arched dam, a dam building of a hydroelectric power station, an operational tunnel spillway and the Tishiklinskaya dam (not part of RusHydro, but belongs to the Selo Chirkei municipality of the Buinaksk region) located 10 km above the dam is intended to protect the valley from flooding the Shuraozen River.

5. General view of the Chirkeyskaya HPP dam and reservoir. The area of ​​the Chirkei reservoir is 42.5 km², the total and useful volume is 2.78 and 1.32 km³, respectively. The concrete arched dam is divided into 18 sections of concreting 16 m wide. It has a crest length of 338 m and a maximum height of 232.5 m. The dam itself consists of an arched part, a wedge-shaped plug and a right-bank abutment. The peculiarity of the dam is that it has a double curvature - it is concave not only horizontally, but also vertically. Thanks to this and its arched structure, its width is only 6 meters at the ridge and 30 meters at the base of the dam.

The base of the dam is a plug 48 m high, 40 m wide and 88 m long at the base, in the lower part of which there is a longitudinal elliptical cavity 21 m long and 21 m span.The central part of the dam 75 m long (four sections) is a station one. On it there are inclined water intakes (from the side of the upper edge) and 4 turbine water conduits (located on the lower edge of the dam).

6. Turbine conduits have a diameter of 5.5 m and an average length of 250 m. For the convenience of monitoring the condition of platinum, 10 galleries have been created at different levels.

8. Another panorama of the Sulak river canyon

9. When we were at the station, the water level in the reservoir was quite low, and we could observe such a picture. All these items can swim :)

10. The inlet of the operational spillway of the Chirkeyskaya HPP, has a span of 22 m, it is blocked by a segmental gate 14 m high. The operational spillway is located on the left bank 85 m from the dam. The throughput capacity of the spillway is 2,400 m³ / s at LPG and 2,900 m³ / s at FPU.

11. Downstream of the Chirkeyskaya HPP

13. The building of the hydroelectric power station is of the dam type, directly adjacent to the dam plug, has a length of 60 m and a width of 43.8 m.

17. We begin our tour of the hydroelectric power station itself and, of course, we are looking for any "raisins". For example, here is one of the tunnels in the body of the dam.

19. And this is the turbine hall, where 4 vertical hydroelectric units with radial-axial turbines RO 230/9896-V-450 produced by the Kharkov Turbine Plant and VGSF 930 / 233-30 generators with a capacity of 250 MW produced by Uralelectrotyazhmash are installed.

Another highlight of the station is the two-row arrangement of these same hydraulic units with a two-tier arrangement of the suction pipes. This made it possible to almost halve the length of the structure. Such a revolutionary solution in hydraulic engineering was implemented for the first time in Russia and there are no analogues in our country. Accordingly, the station has two parallel turbine halls.

21. As part of the modernization program, the equipment is being constantly updated, so soon the last hydroelectric unit No. 2 will be like new

22. And this is the Central Control Panel

25. This is, in a nutshell, the Chirkeyskaya HPP looks like.

Many thanks to the press service of JSC RusHydro, as well as Khaibulaeva Patimat Sirazhutdinovna, head of the public relations group of the Dagestan branch of JSC RusHydro, for such an interesting and rich program.

Another from my Dagestan tour with JSC RusHydro:
Gotsatlinskaya HPP.

The settlement of hydropower Dubki and the Chirkei reservoir. Before perestroika, Dubki, like any other Soviet "scientific" town, flourished - there were branches of the Dagestan Polytechnic Institute, the Kuibyshev Power Engineering College, an educational building complex, a semiconductor plant, a garment factory, 3 cinemas, 5 kindergartens, and a large school.

The diagrams above, in front and in profile of the Chirkeyskaya HPP were borrowed from the site of JSC RusHydro.

The access to the building of the hydroelectric power station is carried out through a road tunnel with a length of more than 800 meters from the right bank.

The Chirkei hydroelectric power station is the pride of Russian hydroelectric builders. The station on the Sulak River is the largest hydroelectric power station in the North Caucasus and the highest arched dam in Russia.
I have never met such a warm welcome and rich educational and excursion program at any industrial facility as at the Chirkeyskaya HPP. We literally climbed the entire station up and down and could not stop, filming until two in the morning ...

1. The Sulak River basin is located in the northern and middle parts of Dagestan. Water from the river is used to supply water to the cities of Makhachkala and Kaspiysk.

2. Chirkeyskaya HPP is a part of the Sulak HPP cascade and is its first stage. I already wrote about other stations of the cascade:
Miatlinskaya HPP is the second stage.
The Chiryurt hydroelectric power plant complex is the third stage.

3. Morning at the largest reservoir in the North Caucasus.

4. The area of ​​the water surface of the reservoir is 42.4 km², and the volume reaches 2.78 km³.

5. The construction of the hydroelectric power station began in 1964 and lasted 14 years. An arched concrete dam with a height of 232 and a ridge length of 338 meters, a hydroelectric dam building and an operational spillway were built.

6. Panorama of the Sulak canyon. It is a pity that the sun rises low at this time of year and only slightly illuminates the crest of the dam.

Enlarge image

7. A road leads to the turbine room through an 800-meter tunnel on the right bank.

8. Top view.

The Google Map will help you to feel the scale of what is happening.

13. With a pressure of 170 meters, water flows at a tremendous speed through the conduits into the spiral chambers of the hydroelectric units.

14. The spiral chamber is designed to supply water to the turbine guide vanes. The water pressure in the chamber is 17 atmospheres.

Enlarge image

15. The guide vanes of the turbine, due to the rotation of the blades, changes the swirl of the flow and regulates the flow rate of the turbine.

16. Water enters the turbine blades. Thus, the energy of the water flow is converted into mechanical energy and transferred to the hydrogenerator, which generates electricity.

17. During our visit, the station was undergoing scheduled overhaul of the 4th hydroelectric unit.

18. Work here.

19. In view of the fact that the Sulak River passes in a narrow gorge, the designers adopted a fundamentally new layout of the hydroelectric power station - a two-row arrangement of hydroelectric units. The machine room is divided into two parts - with two units in each.

20. Two halls - two overhead cranes with a lifting capacity of 320 tons.

21. The first hydropower unit at the HPP with a capacity of 250 MW was connected to the grid in 1974. The last fourth unit was put into operation in 1976.

23. Control room.

24. Transformers and switchgears on the overlap of the powerhouse.

26. HPP capacity - 1000 MW, average annual output 2.47 billion kWh.

28. Thus, the energy of the Sulak River goes through the generator voltage switchgear to the United Energy System of the South of Russia.

29. At 85 meters from the dam there is an inlet of a tunnel-type operational spillway with a length of 730 meters. In the entire history of the operation of the Chirkei hydroelectric power station, water was dumped only three times - such is the arid climate in Dagestan.

30. The tunnel runs at a large slope, then turns into a slightly inclined part, and then turns into a tray with a springboard and side drain-damper. Through such a hole, you can easily spill a whole freight train - no one will notice.

31. Walk through the galleries of the dam.

A small video filmed on the phone:

33. One of the mines in the body of the dam.

34. Technical corridors.

36. The station is especially beautiful at night.

Chirkeyskaya HPP is a hydroelectric power plant on the Sulak River (15 km upstream of the Miatlinskaya HPP) in Dagestan. It is the largest hydroelectric power plant in the North Caucasus and the tallest arch dam in the Russian Federation. Just like the Miatlinskaya HPP is a step of the Sulak HPP cascade ... The Miatlinskaya and Chirkeyskaya HPPs are connected by a serpentine through the Nadyr-Bek ridge, practically on the top of which the town of Dubki hydropower was built in the Soviet years. If you suddenly have to drive along this road, turn onto the dirt road going to the repeater tower - literally a hundred meters from it there is a magnificent natural observation deck, from which you can see both the Miatlinskaya HPP and the Chirkeyskaya HPP and (if you know where to look + have good optics ) the dam of the Chiryurt hydroelectric power station. The Sulak river, the dam of the Miatlinskaya hydroelectric power station and its reservoir. In the distance you can see the village of Old Miatli, described in Leo Tolstoy's "Prisoner of the Caucasus".


The settlement of hydropower Dubki and the Chirkei reservoir. Before perestroika, Dubki, like any other Soviet "scientific" town, flourished - there were branches of the Dagestan Polytechnic Institute, the Kuibyshev Power Engineering College, an educational building complex, a semiconductor plant, a garment factory, 3 cinemas, 5 kindergartens, and a large school. In the 80s of the twentieth century, just in the place where the repeater tower is now located, there was a unique wind field - a place for testing and studying wind power generators. The location was perfect as the wind never stops here. Here, among other things, the wind generators of the Tushino machine-building plant were tested. In the 1990s, known to everyone for its turbulence, the wind farm was abandoned. Some of the wind turbines were taken away, the other part remained in the form of unnecessary majestic ruins.
To the right of the tower is a white mast of one of the wind turbines. The blades from him, torn and twisted by the wind, lie next to him. Other ruined structures of the landfill are unrecognizable even when close. The Chirkei hydroelectric power station was built in a narrow Chirkei gorge with a depth of more than 200 meters (the width of the gorge in the lower part is 15 meters, in the upper part - 300 meters). The main source of power for the Sulak River is melt water of high-mountainous snows and glaciers and rainfall. The construction conditions were very difficult due to the terrain. Work on the main structures of the station began in 1966 with the construction of a construction tunnel 728 meters long and 13 meters in cross section.
Hereinafter, there are archival photographs found on the Internet (unfortunately, their authorship is unknown to me). From left to right, from top to bottom: (1) and (2) - 1965, excavation of the hydroelectric power station pit; (3) - concrete supply by cable-crane; (4) - overlapping Sulak with a directed explosion; (5) - blasting operations to develop the pit and river banks; (6) - installation of the station's pressure water lines. For the first time in the USSR, at the construction of the Chirkeyskaya HPP, the method of contour blasting with preliminary slit formation (the so-called "smooth spalling") was widely used. The construction of the station was interrupted by an earthquake of magnitude 8 in May 1970 - work was suspended for almost six months, during which the slopes were cleared of debris after the earthquake. To secure the unstable rock blocks on the left bank slope of the excavation pit of the HPP building, retaining walls were built in combination with prestressing metal anchors. In inclined wells up to 25 meters deep, 300 tension anchors have been installed. In the horizontal adits, a system of prestressed ties made of high-strength steel with a diameter of 56 mm is installed.
From left to right, from top to bottom: (1) - concreting of unstable massif slopes; (2, upper) - aul Chirkei, which went under flooding; (2, bottom) - a meeting of builders in honor of the beginning of the reservoir flooding; (3) - installation of the stator shaft of the hydraulic unit; (4) - the laboratory assistant takes samples of the concrete mixture; (5) - 1974, the flooding of the Chirkei aul. Three cable cranes with a lifting capacity of 25 tons and a span of 500 meters, working with cylindrical radio-controlled buckets with a capacity of 8 cubic meters, were the main means of mechanization for the supply and placement of concrete mixture into the blocks of the dam. From concrete plants to cable cranes (distance 100 meters), the concrete mix was delivered by BelAZ and KrAZ dump trucks. During the construction of the station, the process of installing and removing the formwork (a special manipulator based on the E-304 excavator), the process of leveling the concrete mixture (a special machine based on the TK-53 crane tractor), the process of removing the cement film from the horizontal surface of concrete (self-propelled cleaning machine based on the DT-20 tractor), as well as other processes and work. Due to the high degree of mechanization of construction, the highest productivity at that time was achieved - 12 cubic meters of concrete per 1 man-day.
From left to right, from top to bottom: (1) - construction of a drainage tunnel; (2) - 02/28/1970, solemn laying of the first cubic meter of concrete in the body of the dam; (3, large photo on the right) - the dam is ready; (4) - the turbine room of the Chirkeyskaya HPP on the day of the start-up of the first unit. The dam was brought under pressure on August 13, 1974. The hydraulic units were put into operation sequentially in 1974 (GA-1), 1975 (GA-2, GA-3), 1976 (GA-4). The Chirkeyskaya HPP was put into commercial operation in 1981.
From left to right, from top to bottom: (1) - pressure water conduits are built; (2) - the final stage of the dam construction; (3) - start-up of the first hydraulic unit; (4) - start-up of the first hydraulic unit; (5) - the settlement of hydro-builders Dubki The structure of the Chirkeyskaya HPP includes: a high-rise arch dam, a hydroelectric power station building, an operational spillway, an open switchgear (OSG) with a voltage of 330 kV. The height of the dam is 232.5 meters, the length along the ridge is 338 meters. The central part of the dam is a station. The water intake structure is an inclined reinforced concrete structure placed on the upper edge of the dam. 4 pressure turbine conduits with a diameter of 5.5 meters (plus 1.5 meters of reinforced concrete shell) originate from its water intake openings.
View of the dam, reservoir and the station building from the observation deck of the right bank. The diagrams above, in front and in profile of the Chirkeyskaya HPP were borrowed from the site of JSC RusHydro. The building of the Chirkeyskaya HPP (unlike the Miatlinskaya HPP) is of the dam type and is located directly at the lower edge of the dam plug. In order to place the aggregates with minimal incisions into the steep walls of the gorge, a project was carried out for a pair of aggregates (2x2 parallel with a common mounting platform in the middle). In this case, the transformers are located on the roof of the turbine hall. This original solution has no analogues in the practice of hydroelectric construction.
The building of the hydroelectric power station and the transformer site on its ceiling.
Dam and fortifications of the rocky massif of the left bank.
Valve valve of pressure water conduits of the operational part of the dam.
The Chirkei reservoir has an area of ​​42.4 square kilometers, its capacity is 2.78 cubic kilometers. When the reservoir was created, the old village of Chirkey was flooded - it was moved to a new place.
Outdoor switchgear-330 kV and the waterworks control building are located on the right top of the gorge.
Among the outbuildings of the hydroelectric power station, one can see massive concrete cubes - these are the foundations of the cable-cranes with which the station was erected.
The access to the building of the hydroelectric power station is carried out through a road tunnel with a length of more than 800 meters from the right bank.
Sulak after the downstream of the Chirkeyskaya HPP. The idle spillway is made in the form of a tunnel with an open drain chute inside the rock of the left bank. There is an entrance opening 85 meters from the dam with a span of 22 meters. A tunnel (width - 9 meters, height - 12 meters) with a length of 160 meters runs from it at a large slope. Then it goes into a slightly inclined part with a length of 350 meters and only then into an open 200-meter chute with a springboard and a side damper drain. In my opinion - a great water park.
In view of the extreme failure of my own photograph, I used a photograph from the site of the United Dispatching Office of Power Systems of the South www.yug.so-ups.ru. The photo shows the entrance portal of the idle spillway.
Chirkeyskaya HPP from the lower observation deck. A massive spillway tray is perfectly visible on the right.

Transformer site and left bank.
Concrete wall.
Transformer site and right bank.
An unusual feeling when standing next to such a colossus. Due to the fact that the dam is arched both in length and in profile, it hangs over you with a huge canopy.

Well, again, the view from the lower observation deck.

It will be about the largest hydroelectric power station in the North Caucasus - the Chirkei hydroelectric power station.

I have long dreamed of getting to this dam and I was lucky: I had two days at my disposal and free movement around the territory of the hydroelectric power station and not only. I managed to shoot the dam day and night, to visit all of its hard-to-reach places. I even slept on the territory of the hydroelectric power station under the noise and vibration of hydroelectric units, and not somewhere in a hotel.

The Chirkeyskaya HPP is located in a picturesque gorge on the Sulak River in the Buinaksky district of Dagestan, is a part of the Sulak HPP cascade, being its upper stage that regulates the entire cascade. The Chirkeyskaya HPP dam is the second tallest and highest arched dam in Russia.

2. The dam is 232.5 meters high. Crest length - 338.

3. The dam forms the Chirkei reservoir of long-term regulation (its capacity allows to accumulate water in high-water years and use it in low-water years). The area of ​​the reservoir is 42.5 km², the total and useful volume is 2.78 and 1.32 km³, respectively. At the time of filming, the reservoir level had not yet reached the normal level.

4. Black stripe on the rock - the usual level of the reservoir.

The electric power of the station is 1000 MW. These are 4 hydropower units of 250 MW each. They are located in the dam building of the hydroelectric power station. A special feature is a two-row arrangement of hydraulic units with a two-tier arrangement of suction pipes.

5. The building of the hydroelectric power station has two parallel turbine halls due to the peculiarities of the location of the hydroelectric units.

6. Turbine hall

7. We go down below - the rotor of the hydrogenerator.

8. Even lower is the shaft connecting the generator rotor with the turbine.

9. Even lower - the spiral chamber - the place where water enters the turbine and spins it up.

10. Reconstruction of the hydrogenerator.

12. Downstream.

Chirkeyskaya HPP is the largest hydroelectric power plant in the North Caucasus. Having high maneuverability, it is the main control station in the United Energy System of the South of Russia, operating in the peak part of the load schedule. Also, it performs the functions of a kind of "ambulance" in the power system, allowing in the event of an emergency exit of 150-300 MW units at thermal power plants to quickly replace the retired capacity. Due to the presence of a counter-regulator - Miatlinskaya HPP - the station has no restrictions on discharge regimes, having the ability to quickly change its capacity (and, accordingly, the downstream flow rates). By deeply regulating the flow, the Chirkeyskaya HPP increases the output at the downstream stations of the cascade, as well as ensures a reliable water supply settlements and irrigation.

13. Turbine water lines.

14.

15. Let's go back to the dam itself and the reservoir.

16. Due to the fact that the level of the reservoir was low enough, you can see the water intakes of the hydroelectric power station. The dam has a double curvature, like a hemisphere - it is concave not only horizontally, but also vertically. This also shows up in the photographs.

17. Panorama of the complex of structures.

18. Panorama from the ridge of the dam. Due to its double-curved arched structure, the dam is quite thin - only 6 meters at the ridge and 30 meters at the base of the dam - a concrete plug 48 m high, 40 m wide and 88 m long at the base.

The dam is closed, but there are exceptions. Along the crest of the dam, sheep are transferred from winter pastures to summer pastures and vice versa. I myself did not find this, thanks to Gamzat Magomedzagidovich for the photo provided.

19. Observation deck. The cylinder is the elevator shaft.

20. The inlet of the tunnel-type operational spillway. An eerie sight. The throughput capacity of the spillway is 2400 m³ / s at LPU and 2900 m³ / s at FSU. The entrance hole has a span of 22 m. A train could easily be dropped there. Nobody would have noticed.

21. The entire water column is supported by such a segmental gate with a height of 14 m. At the time of filming, the reservoir level was so low that the water was lower than the gate.

22. I propose to go down into the spillway tunnel and see how it looks inside.

23. Thanks to Gamzat Magomedzagidovich, a specialist at the Chirkeyskaya HPP, I got inside the tunnel. I am grateful to this man for the fact that from early morning until late at night he walked with me to all hard-to-reach places and along the way told me interestingly about the station.

24. Beginning of the inclined section.

25. The tunnel itself has a horseshoe shape, with a height of 12.6 meters. I can imagine what's going on here when the spillway opens.

26. At the exit from the tunnel.

27. Wait for the night. The station does not have decorative lighting, but it is sufficiently well illuminated with conventional floodlights.

30. View down from the ridge of the dam.

32. Downstream.

33. Transformer site.

34. At night, only a few people remain on duty at the station, this is enough to operate the entire station.

35. I stayed overnight at the hydroelectric power station in the hope of catching the morning fog, and the time was too late to go to the neighboring village, therefore, to the noise and vibration, I fell asleep comfortably right in the building of the hydroelectric power station. Unfortunately, there was no fog.

36. On the second day, I, together with Mukhtar, an operative of the station, climbed from the lower pool to the upper one along the stairs along the entire dam.

37. There are a lot of tunnels in the body of the dam for monitoring filtration and other various parameters, therefore there are many balconies.

38. At one of the turbine pipelines.

39. Power lines that go to the 330 kV outdoor switchgear.

43. Tunnel, of which there are many in the body of the dam and in the rocks.

45. A fish farm has been organized at the station, specializing in trout breeding. The trout is delicious, I tried it myself. Thanks to Bagavdin Nasrudinovich.

46. ​​In the Conclusion there will be photographs of the Chirkei Gorge, the depth of which is more than 200 meters.

51. Here you can already see the Miatlinskaya HPP - the counter-regulator of the Chirkeyskaya HPP.

52. Miatlinskaya HPP, I will talk about it next time.

I would like to thank the Dagestan branch of JSC RusHydro for organizing the trip and for the warm welcome in general!

Thank you for the attention.