The Three Gorges Dam continued to receive 'water bombs' from upstream and obscure 'secrets'
The Three Gorges Dam, the largest hydroelectric dam in the world located on the Yangtze River (also known as the Yangtze River) of China, still has little-known secrets. Currently, the Three Gorges dam is buckling against the growing pressure caused by floods coming from upstream like 'water bombs', threatening the safety of the dam.
According to Neikei Asia Review, on August 21, for the first time in history, the amount of water in the reservoir of the Three Gorges dam has reached a height of 166 meters, meanwhile, the maximum height of this dam is 175 meters.
In response, the Tam Hiep Dam management agency opened 11/14 flood gates a day earlier with the water discharge downstream up to 49,200 m3 / second.
The emergence of the emergency situation caused the emergency response system to prevent floods to level II, the second highest level in China's four-tier system.
Several other reservoirs upstream of the Yangtze River, such as Ertan and Xiangjiaba, were also directed to accumulate water to help reduce the flow into the Three Gorges dam reservoir.
In fact, this giant dam has undergone many tests before officially put into operation in 2003.
Test with 190 tons of dynamite
The Tam Hiep Dam is expected to control floods. In many tests there was a final test of a load of 190 tons of explosives that knocked over the wall adjacent to the main dam.
The Yangtze River is 6,300km long and has some parts of the river bed more than 1km wide. This is a huge river in China, so building dams on this river poses great challenges ever. The Truong Giang River warehouse rose up behind the Three Gorges dam, inundated more than 60,700 hectares of land along the banks of the Chinese government, displacing more than half a million people living in the land behind the dam. Then, engineers began to build dams on the riverbed.
First, they will prefabricate large concrete blocks to form a wall to prevent water to control the river during the construction of the Tam Hiep Dam.
According to Chinese engineers, this is the largest and most difficult diversion activity undertaken in dam projects because of its enormous scale. A series of walls were built on the riverbed, they only left a part for river water to flow through. They built the first two sections of the dam on the very dry riverbed, then they poured tons of soil into the river, on which the engineers built another wall with concrete. With the riverbed remaining behind the wall, the engineers were able to finish the final stretch of the dam.
When construction was completed, they had to remove the wall so that water could flow through the main dam's turbines.
So how did they remove that giant wall? Unlike the wall in other projects, the water barrier at Tam Hiep Dam is too high, so the demolition of the wall needs creativity. The wall's engineers left plenty of room to bury explosives.
On June 6, 2006, they buried 190 tons of explosives and counted down nervously. The wall took months to build, but only a few seconds to destroy, releasing the water in the back. That was also the last test with the Three Gorges Dam and the dam still standing.
In fact, on the longest river in Asia, besides the giant Three Gorges Dam, there is another dam, the Cat Chau Ba Dam (Gezhouba). Both dams are located in Nghi Xuong, Hubei province.
Cat Chau Ba Dam is located in the downstream area of Tam Hiep Dam, about 38 km away. The Cat Chau Ba Dam was completed in 1988 and the Three Gorges Dam was put into operation in 2006. The Three Gorges Dam became the largest hydroelectric plant in China as well as in the world, and the second largest Cat Chau Ba dam. in China.
How much electricity can the Three Gorges Dam generate?
According to Chinaguide, the Three Gorges Dam is the largest concrete gravity dam, also the largest water control project in the world to date.
Its total installed capacity is 22.5 million kWh, and the annual generating capacity can reach over 100 billion kWh, mainly transferred to Hubei, Henan, Hunan, Jiangxi, Chongqing provinces, Shanghai, Jiangsu, Zhejiang, Anhui and Guangdong.
With the grid electricity tariff of 0.25 RMB / kWh, the Three Gorges Dam's revenue from power generation will be more than 25 billion yuan ($ 3.6 billion) per year.
Compared with the Itaipu Dam - the second largest hydroelectric dam in the world, on the Paraná River located on the border between Brazil and Paraguay, with a total installed capacity of 14 million Kwh and annual capacity of 90 billion Kwh, the Tam Gorges dam far exceeds, truly deserves the title of giant, largest in the world.
It is known that the total investment capital for the construction of the Three Gorges dam is 203.9 billion yuan (24.65 billion USD).
How can the Three Gorges dam withstand floods?
The Three Gorges Dam is like an iron fortress. It was built of 27 million tons of concrete, 463,000 tons of steel, and excavated 102.6 million cubic meters of soil. The dam wall is 181 meters high against the rock.
In addition, the Three Gorges Dam is a concrete gravity dam and each part of the dam can ensure its stability depending on the gravity of the dam. Even if one part is damaged, the entire dam will not collapse, and it can be directly repaired.
The Tam Hiep Dam has a capacity of 22.15 billion cubic meters and a maximum water capacity of 39.3 billion cubic meters. With normal floods, the Three Gorges Dam can be completely controlled. In the event of a major flood, flood prevention and storage measures will be in place to reduce the flooding.
However, the flood control capacity of the Three Gorges dam and the reservoirs in the Yangtze River basin is less than 20% of the annual water flow of the river. If a single flood occurred, the main part of the Three Gorges Dam would not be destroyed, but its function would be affected.
There was recently information on the danger of breaking the Three Gorges dam after heavy rains and floods that lasted for a month in China.
The dam construction is reported to be of poor quality, with large cracks appearing in the dam body in 2000, leading to prophetic criticism of potential disasters similar to those of the Ban Kieu dam. 1975.
Two risks have been agreed upon for the dam. It is a sedimentary pattern that has not been thoroughly examined and this dam is located on a seismic fault. Excess sediment can block water outlets, and it can damage dams in some situations. This is the cause of the 1975 Ban Kieu dam failure, which damaged 61 other dams and caused the deaths of more than 200,000 people.
In addition, weights of dams and reservoirs could theoretically generate induced seismicism, as happened with the Katse Dam in Lesotho.
