Three Gorges Dam, World’s Largest Concrete Giant
The Three Gorges Dam is the biggest concrete dam in the world constructed on the Yangtze River in Hubei province, China. The dam is 2.2 Km long with 60 stories and a height of 160m. 40,000 workers worked on it for 17 years; starting in 1994 it became operational in 2012. It will produce 22,500 Megawatts of power twice as much as all nuclear power stations in Britain together. The total cost of the project was about 31 billion dollars. The electricity produced by this single dam can be used by the whole of Pakistan as Pakistan's total need in June is about 23000 megawatts.
Background:
China is one of the fastest-growing economies of the world. To fuel its ever-accelerating industry it needs more power. The idea of Three Gorges Dam was given when Mao Zedong ordered to study sites for construction of the dam. The purpose of construction was to control disastrous flooding in the Yangtze River and to fulfill the need for power for industry. However, there were key problems including the danger of dam collapse, displacement of 1.2 to 1.9 million people from 1500 towns surrounding the Yangtze River, destruction of significant architectural and archeological sites. Some Chinese and foreign engineers argued that a number of smaller dams can control flooding with lesser risks. Due to these factors, it took 40 years to finalize the project. World Bank refused to transfer funds to China for the construction of the dam due to environmental and other concerns.
Construction:
Before the start of construction, the Chinese had to divert the Yangtze River which is 2 Km wide. When they stopped the water by a reservoir behind the dam, the huge mass of water actually slowed down the earth’s rotation by a fraction. The Yangtze River, the largest river of China is 6000 Km long and at some places several kilometers wide. When the Yangtze River rises from 3 gorges it is expected to flood 150,000 acres of land.
Three Gorges Dam is the biggest hydroelectric project in the world. In its construction, 28 million cubic meters of concrete and 463,000 metric tons of steel were used. Just for comparison, 330,000 cubic meters of concrete were used in Burj Khalifa. By this, one can imagine the magnitude of the dam. The dam consists of 32 generators, each having a cost of 50 million dollars.
Firstly, cofferdams were constructed to block two-third of the magnitude of water. After construction of 2 gorges, coffer dams for these portions were removed then cofferdam for the third portion was made. On 6th June 2006, 190 Tons of dynamite was filled in holes of cofferdams to remove them. With the destruction of cofferdams, water rushed towards 3 Gorges Dam and it stood in front of flowing water as a magnificent giant of concrete.
3 Gorges Dam used concrete 10 times more than Hoover Dam. With this colossal amount of concrete, they have to take precautions to keep the temperature of concrete as low as possible. They cooled aggregates, sand and other materials with the addition of ice in the mix. Because high temperatures can cause significant problems in concrete. Due to summer weather, they used a fog spray system along with fog blankets to stop solar radiation. Chinese engineers used high-pressure pumps to pump grout into pores in the foundation. With pumped grout, the pores between rocks were filled and eventually, it turned into an impermeable layer.
Three Gorges Dam can hold 22 billion cubic meters of water and then it is released into a system of 46 spillways. Once the water level rises, a series of gates were opened to drain the floodwater from the water. However, if water fell straight that will undermine the foundation. Therefore, the engineers fit the spillway with concrete shoes. These concrete shoes help to shoot water into the air in the form of droplets that will reduce its destructive energy.
The Yangtze River is one of the busiest rivers in Asia. One hundred and seventy ships a day with tons of cargo pass through the river. So, the Chinese build the biggest ship block on earth. The ships enter through the bottom of the dam the gates behind ships are closed and the water will enter and the lifts the ships up to the next block and it takes 4 hours to move through 5 blocks. But for passenger ships they have made an elevator system with 16000 tons of concrete blocks that will lift the ship with water and in 36 minutes ship will be on another side of the dam.
As Yangtze River is notorious for flooding and one major flood after 10 years causes a lot of destruction so, in addition to the production of power the main reason behind the construction of Three Gorges Dam is to control flooding and Three Gorges Dam is serving its purpose very efficiently by controlling floods.
Article by:
Muhammad Usama Gujjar
