A dam is a structure that helps block the rise or flow of water 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-Karaf", which is found in the records of Herodotus. Regarding her age, experts disagree. Some believe that it was built in 3200 BC, others - that in the interval between 2950-2750. BC.
What was the oldest dam made of?
How big was the oldest dam? This impressive structure was a double stone wall, between the sides of which fragments of stones were additionally thrown. The length of the dam was more than 100 meters along the crest, while the height reached 12 meters. A similar project allowed the accumulation of up to two million cubic meters of water in Wadi al-Gharavi.
The Chinese built on a large scale and for centuries
Some historians believe that dams in the Bronze Age were built everywhere at the points of development of one or anotherlocal 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. Here the master, and later the emperor Yu, became famous, 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 erected. It was a large-scale construction 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 such an element as an arch was born.
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 the 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, and also taking into account the accumulated experience that came to Europe after contacts with the Arab world. For example, it is known that even such, at first glance, not very strong structure, like an earthen dam, was operated for a century,before collapsing (was erected in France in 1196).
The use of dams in Russia
For Russia, with its rich water resources, also, at first glance, dams were not particularly required. However, they have existed here since the 14th century AD and were used in water mill systems. The first mention of dams is noted in the will of Dmitry Donskoy, dated 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 stood out a high earthen dam - Zmeinogorskaya. Water resources through such devices were transferred for use in textile, mining and other enterprises of that time.
A dam is a hydraulic structure that can be related to one or another type of object, depending on the classification. Today, there are reservoir, water-lowering and lifting devices. Reservoir dams are usually very high and have the ability to control the release of water. Low structures (for example, for constructing ponds) usually do not have a runoff. Another important classification is the division of objects depending on the depth of the water in front of the seal. Here, low-, medium- and high-pressure dams are distinguished (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, arrange a waterfall, the power of which can somehow be used; in order to make a shallowpart of the river passable for ships), and along (to protect against floods). In some cases, streams, ravines, and hollows are blocked by dams to hold melted snow water in them, which are then used for irrigation or for feeding navigation channels.
Main elements of HPP
The structure of hydraulic structures usually includes a dam, a reservoir in front of or after it, a water-lifting installation, a complex of hydroelectric power plants, slopes for the passage of fish, a water drain (if the system is a culvert), structures for strengthening the coast and 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 of the Ministry of Emergency Situations, holding on themselves sheets of film that prevented water from overflowing over the tops of the existing protective structures.
How can dams take the load?
Another classification of dams reflects how these objects resist loads. Gravity buildings perceive impacts with their entire mass and resist due to the adhesion of the sole of the dam and the foundation on which it stands. Such options are usually very massive. For example, a 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 arched-gravity models or arches with buttresses at the base. Buttress options have a thinner dam wall, but a reinforced base due to supporting elements. Dams are being built today using the bulk or alluvial method, as well as the directed explosion method.
Consequences of accidents
Accidents at dams bring with them significant material losses, as not only unique equipment is destroyed, but also enterprises that operate on electricity and water supplies from this dam stop. Sometimes entire settlements are washed away by water flows, crop areas are flooded, crops are lost. But the worst thing is that dozens, hundreds and even thousands of people can die almost instantly.
So, in March 1928, in the San Francisco Canyon, the destruction of the St. Francis Dam occurred, 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 breakthrough site. In the USSR, during the Great Patriotic War (1941), a decision was made to deliberately undermine the Dneproges dam in connection with the occupation of Zaporozhye by fascist troops. The massive concrete structure was partially damaged with 20 tons of ammonal. How many people died then is still not exactly determined. The figures are from twenty to one hundred thousand people, including troops, refugees and the population, which could be on the left bank of the Dnieper, which took the brunt of the water element.
The total number of victims is about 230 thousand people
Post-war dam accidentslarge power plants entailed even greater casu alties. In August 1975, when the Banqiao dam burst, only 26,000 people were drowned, 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 the maximum amount of precipitation, 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 break, a number of measures are being taken today, including compliance with the design parameters of the dam, checking for compliance during work, observations during operation, collecting visual and geodetic information, etc. For dams, there are two inconsistencies with project requirements and standards: "K1" - the object has a potentially dangerous state and urgent measures are needed to eliminate its causes, and "K2" - a pre-accident state, destruction is possible, rescue and evacuation work is needed.
