A dam is a structure that helps block the rise of water or its flow for various purposes. 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 between 2950-2750. BC.
What was the oldest dam made of?
What size 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 over 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-Garavi.
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 another local civilization. For example, in Mesopotamia, a stone structure dating from the seventh century BC was found. In ancient Syria, similar structures were built one and a half thousand years before the birth of Christ. (Nahr al-Assi). Large-scale construction of dams was observed in ancient China. Here the master became famous, and later Emperor Yu, who in 2283 BC, the current ruler entrusted the management of all water construction in the empire. Under the leadership of the Great Yu (as it is still called), more than one dam was erected. It was a large-scale construction for centuries and millennia, which allowed by 250 BC to irrigate, for example, 50,000 square kilometers in the Sichuan deserts due to 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 was born.
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 the Spanish annals in 1586, but engineers believe that the devices themselves could be 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 solid construction, like an earthen dam, was exploited for a century before it collapsed (it 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 needed. However, here they existed from the 14th century AD and were used in watermill 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 in the Russian Empire there were already more than 200 objects, among which stood out a high earthen dam - Zmeinogorsk. 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 relate to one or another type of object, depending on the classification. Today they distinguish reservoir, drainage and lifting devices. Reservoir dams are usually very high and have the ability to regulate water discharge. Low structures (for example, for the construction of ponds) usually have no runoff. Another important classification is the subdivision of objects depending on the depth of water in front of the floodplain. Low, medium and high pressure dams are distinguished here (up to 15, 50 and more than 50 meters, respectively).
Dams for rivers and ravines
Dams on rivers can be erected both across (to raise the water level, equip a waterfall that can be used somehow; to make the shallow part 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 melt snow water in them, which are then used for irrigation or to feed shipping channels.
The main elements of a hydropower plant
The structure of hydraulic structures usually includes a dam, a reservoir before or after it, a water installation, a complex of hydroelectric power stations, descents for fish passage, water discharge (if the system is culvert), structures to strengthen the shore and clear the system of 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 film canvases that did not allow water to overlap through the tops of the existing protective structures.
How dams can 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, 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 transmit pressure to the shores. If the arch is wide and the pressure is high, then arch-gravity models or arches with buttresses at the base are used. But buttress options have a thinner dam wall, but a reinforced base due to retaining elements. Dams are being erected today using the bulk or alluvial method, as well as the directional explosion method.
Accident consequences
Dam accidents incur significant material losses, as not only unique equipment is destroyed, but enterprises that operate on electricity and water from this dam are also stopped. Sometimes whole settlements are washed away by water flows, the sown areas are poured, the crop is lost. But the worst thing is that tens, hundreds and even thousands of people can die almost instantly.
So, in March 1928, in the canyon of San Francisco, the dam of St. Francis was destroyed, then about six hundred people died, and many-meter pieces of the dam itself were found at a distance of about a kilometer from the place of the breakthrough. In the USSR during the Great Patriotic War (1941), it was decided to intentionally undermine the Dnieper 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 precisely determined. They call the numbers 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 main blow of the water element.
The total number of victims is about 230 thousand people.
Post-war accidents at the dams of large power plants entailed even greater casualties. In August 1975, when the Banqiao Dam broke through, only 26,000 people were drowned, and taking into account the widespread epidemics and starvation, the death toll reached 170-230 thousand people. At that time, about a third of a million cattle 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 the water masses brought by the typhoon Nina. On August 8, 1975, the smallest of the dams collapsed, resulting in a discharge of water in Banzao, 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 the breakthrough of the dam, a number of measures are being taken today, including compliance with the dam design parameters, checking compliance with the work, observing during operation, collecting visual and geodetic information, etc. For dams, there are two discrepancies between the requirements of the projects and standards: "K1 "- the facility has a potentially dangerous condition and urgent measures are needed to eliminate its causes, and" K2 "is a pre-emergency condition, possibly destruction, rescue and evacuation work is needed.