Photographer @ jiandanqinxin)} they can also raise water level, develop hydropower and improve water quality Waterway (the brightly lit Baihetan Hydropower Station will become the second largest hydropower station in the world after the Three Gorges hydropower station, photographer @ chaijunfeng) China also has the largest number of reservoir dams in the world (according to the code for design of rolled earth rock dams (2001), the dam body can be divided into three types according to the height: < 30m for low dam, 30-70m for medium dam and > 70m for medium dam High dams; the figure below shows the number of dams with a height of more than 30m in the world’s major countries, cartography @ Zhengyi / planetary Research Institute)} how did we build such a large number of dams? The oldest earth dam was born (there are many types of earth dams, and the figure below is a sketch of homogeneous earth dam, drawing @ luozihan / Xingxing Research Institute) @ @ the compacted soil particles greatly enhance the stability of the dam body by closely occluding with each other, and the pores between the particles are significantly reduced Blocking the flow of water makes it have a strong anti-seepage function, so as to realize the “soldiers come to block, water comes to cover the earth” (anti-seepage comparison before and after soil compaction, cartography @ luozihan / Xingxing Research Institute)} even when the conditions are enough and ideal, without mechanical compaction, the dam can be compacted layer by layer by virtue of the weight of the soil itself (the above damming method is called water filling method, Fenhe River on the Loess Plateau) Reservoir dam is the world’s first dam constructed by filling with water
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Photographer @ Lu Jiechen)} they can store water and ensure water supply and irrigation (please watch horizontally
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Source: Institute of planetary studies
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In front of the picture, it flows out through the power station Water body, image source @ visual China) @ @ or inclined layout of impervious wall is inclined wall rockfill dam (structure diagram of inclined wall rockfill dam, drawing @ luozihan / planetary Research Institute) @ @ the well-known Xiaolangdi dam is 160 meters high, which is the highest inclined wall rockfill dam in China (please view horizontally, the majestic Xiaolangdi dam is 1667 meters long and 15 meters wide, located in the middle reaches of the Yellow River, photo taken It’s such a dam that makes the water storage of Xiaolangdi Reservoir reach 12.65 billion cubic meters, and more than two Taihu lakes
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In July 2020, nine outlets of Xin’anjiang reservoir will be released
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On the other hand, the loose earth rock surface is difficult to resist the fierce water flow Therefore, the earth rock dam does not allow flood overtopping, so it is necessary to add a special flood discharge channel far away from the dam body (Shuibuya dam and the spillway on the right, click on the picture to see the flood discharge scene, and the photographer is @ Li shunwu @ Tan Jianghong)} so how can we build a more solid dam? 02
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Until the 1980s, China began to introduce a new type of equipment, such as vibrating roller After being rolled by the same super strong “roller”, the stone particles are dense, the hardness is increased, and the anti deformation ability is greatly enhanced, which is equivalent to that of concrete (construction scene of rockfill dam, photo source @ visual China)} since then, the rockfill dam can finally obtain the reinforcement of concrete
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If you put a huge rock in the water, as long as its weight is enough, it can produce enough strong friction with the foundation to make it stand still in the turbulent current
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The two different degrees of deformation make them unable to “work together” to resist the surging rivers
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China is one of the countries with the largest number of rivers in the world, with more than 45000 rivers crisscrossing over the land of 9.6 million square kilometers (the number of rivers mentioned above only includes rivers with a drainage area of 50 square kilometers or more, and the following figure shows the distribution of major rivers in China, cartography @ Zhengyi / planetary Research Institute)} China is also the country with the most floods and droughts in the world There are 1092 floods and 1056 droughts recorded in many countries, which make the thousands of years of Chinese civilization history a history of people’s struggle against floods and droughts (the above data are only counted until 1949, and the picture below shows the Qiantang River in the flood, photographer @ Xiao Yisan) No country has developed into one of the most developed large-scale water conservancy facilities in the world, among which the most prominent is the nearly 100000 dams with a storage capacity of nearly 900 billion cubic meters all over China (according to the International Commission on dams, dams with a height of more than 15 meters, or with a storage capacity of more than 3 million cubic meters and a height of more than 5 meters are dams
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Similarly, if you can build such a huge rock artificially, it can resist the rushing water of the river with its “own strength”, which can be called “one man can’t open” and this is gravity dam (gravity dam) For this reason, the hard and dense concrete has once again come into people’s sight
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Because of this, the flood control standard of the lower Yellow River has been raised to once in 1000 years, and nearly 100 million people have been protected from floods (the water storage of Taihu Lake is about 5.6 billion cubic meters, and the following picture shows the flood discharge scene of Xiaolangdi dam, photographer @ Zhang Ziyu) Only the soil concrete has even smaller pores and stronger anti-seepage, but it is too “hard” compared with the rock fill dam concrete whose particles are loose and easy to deform slightly under the pressure of water
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On the one hand, no matter how compacted the pores between the particles still exist, it is inevitable that seepage will occur over the years
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As long as a layer of concrete slab is laid on the upstream side of the dam, the anti-seepage can be completed, which is the concrete slab Rockfill dam (structural sketch of concrete faced rockfill dam, drawing @ luozihan / Xingxing Research Institute) @ @ @ due to its fast construction and low cost, this type of dam quickly became popular all over the country
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Due to its easy access to materials, simple structure and simple construction, they are widely used
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However, unlike fine and dense soil materials, the coarse particles and high hardness of stone materials are prone to water seepage, and even mechanical compaction has little effect Therefore, engineers use stone and soil materials to form a core rockfill dam (core rockfill dam structure diagram, drawing @ luozihan / planetary Research Institute) @ (Bikou reservoir dam is a core rockfill dam, located in Wenxian County, Gansu Province
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The Shuibuya dam in Enshi, Hubei Province, with a height of 233m, became the highest concrete faced rockfill dam in the world at that time (Shuibuya dam on Qingjiang River, with Z-shaped raceway visible on the dam body, used for drainage, maintenance, maintenance, etc.) Transportation, etc., photographer @ Li Yunfei) the above dams built with earth and stone materials are collectively referred to as earth rock dams
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According to relevant data statistics, in China’s nearly 100000 dams, the number of earth rock dams accounts for more than 95%, almost all over the country Earth rock dam, located in Putian, Fujian Province, photographer @ DJY Junyi) @ @ @ but even if the amount is so large, the earth, gravel and other dam materials are loose particles, which means that the earth rock dam is not perfect
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The concrete gravity dam poured by it can not only block water and cut off the flow, but also is strong enough to set a discharge hole on the dam body, or even build a dam section that can overflow directly (Danjiangkou Dam, which is discharging water, is located in Danjiangkou, Hubei Province, photographer @ baifufan) .
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Of course, in addition to pebbles, sand, and artificially mined stones, they can be used to build dams, which are called rockfill dams
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Xinfengjiang reservoir is one of the important drinking water sources in many cities such as Hong Kong and Shenzhen
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The following figure shows the distribution of dams with a height of more than 100 meters in China/ They can hold water and intercept torrents (please watch horizontally
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It is located in Taiyuan, Shanxi Province
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