From the waters of the Yangtze River and China rises the biggest concrete structure on the planet the three Gorges dam is over two kilometers long and 60 stories tall. It has taken 40 thousand workers over 17 years to build when it fully comes online this one damn will produce over 20,000 megawatts of power twice as much as all the nuclear power stations in Britain put together it is the pinnacle damn. Engineering china is one of the fastest growing economies on earth fuel the need of its ever-accelerating industry the nation needs more power much of this will be provided by an enormous damn spanning the mighty galaxy River in central China called The Three Gorges Dam. Our cameras have been granted privileged access to capture this amazing feat of engineering in its full glory before they could start building the Three Gorges Dam the Chinese first had to divert the Yangtze River which is almost two kilometers wide. And move over a million people from the area about to be flooded and when they filled the reservoir behind the down a huge mass of water actually slow down the speed of the Earth’s rotation by a fraction Three Gorges dam is the biggest hydroelectric project in the world. This damn use 28 million cubic meters of concrete maybe one way to look at it is to say so solid Piper concrete a meter diameter right around the world a lot of concrete the Chinese authorities.
Think it’s worth the effort as the three gorges dam will provide clean and cheap electric power to millions of people British engineer Robin childhood has been working on the damn since 2003. And is still impressed by its scale we’re in one of the three very large power houses in the Three Gorges project in this seven hundred meter long from here you can see 14 large turbine generators. Then they’re on this one kilometer away is the second power house and then beyond that one has yet another power house which be underground in the rock by the fire side of the river each one of these generators cost about fifty million dollars. Give you an idea of the scale of this project dead and damn have one generator Three Gorges has 32 together they produce five million times more power than depth to drive them the Chinese. Have harnessed the power of the mighty Yangtze River in the reservoir behind the dam the river now rises up to 60 stories above the river band the water is channeled down gigantic concrete tubes toward the generators.
The torrent of water hits the turbines and makes them spent this motion is in turn transferred to the rotor of degenerate this is fitted with massive magnets. Which moved past copper coils in the casing to generate electricity just one of these machines makes as much electricity as a small nuclear power plant all 32 generators together produce enough power for 60 million Chinese. This project is setting a new benchmark in the international hydroelectric industry it’s almost twice the size of the next largest project it’s either in Brazil and of course it’s only the first of a whole series of negative ads that are under construction. In China the Yangtze river is over 6,000 kilometers long and in places several kilometers wide the biggest river in China it presents enormous logistical challenges to the damn engineers.
As the Yangtze rises behind the Three Gorges down it will flood over a hundred and fifty thousand acres of land along its banks so the Chinese have to relocate over a million people from the land behind the dam thousands of new houses have to be built for the display citizens to live it then the engineers can begin to dam the river. We’re standing among some of the rocks and these precast concrete blocks that we use to create the coffer dams to control the river during the construction of the Three Gorges project controlling the river so allow the construction of this huge project. Was clearly a major undertaking and with the Yangtze river is one of the largest rivers in the world very fast very deep so building these coffer dams and to allow a safe construction was a major operation. The Chinese claim that this was the largest and most difficult diversion ever undertaken for hydroelectric project. And you look at the scale of it they were absolutely right this was huge the engineers begin work on a series of stone cofferdams to block off part of the AXI. Whilst leaving a channel open for the rest of the river to flow through they build the first two sections of the main damn on the dry riverbed. Then they dumped tons of Earth into the river and on top of it build another cofferdam this time from concrete with the river held in check behind it. They can finally build the last section of the ban, and then they must remove the cofferdam so that water can flow through the turbines of the main down having built such substantial cofferdam structures. It’s a major challenge how to remove these things so in the in the earlier stages where they were built of very large rocks like this then that could be handled with big X greater equipment relatively conventional.
But in the final stage where they had a solid concrete wall to remove this required some serious innovation unlike the cofferdam in my rage. The Chinese version is too tall to simply leave it in place so the Chinese engineers build it leaving holes for explosive charges on the sixth of June 2006 they filled them with a hundred and ninety tons of dynamite and hold their breath. What has taken months to build takes only seconds to destroy as the cofferdam crumbles it unleashes the water stored behind it it’s the final test for the Three Gorges Dam and it holds the Three Gorges Dam takes concrete construction to new heights. You look at it you can just picture the thickness of a concrete at the base of the dam hydrate 280 meters and it’s two kilometers long so it’s a colossal amount of concrete three gorges uses 10 times. More concrete in the Hoover Dam so the engineers have to pull out all the stops to keep their damn cool they basically use everything in the book they cool the aggregates and the materials.
That sounds before they put it into the mix they added ice they did everything they could to get the temperature down as low as they could before it started to warm up all by itself. And because of the issue some of the summer weather being especially hot July and August they actually went so far as to use a fog spray system to blow effectively a fart blanket over the top of the dam. With the objective of blocking the solar radiation from piling down into the concrete and adding to the heat that was being generated on the inside but all these measures to stop concrete and cracking will count for nothing.
If the dam is built on weak foundations a civil engineer and McCann explains why we can make the dad completely impermeable throughout the harder for us to make the riverbed impermeable. Now of course once the war is up behind the dam is a huge pressure pushing it this way and whilst the downward at the water through the wall would simply just goes underneath. And that means you haven’t got much of a dam. There is a solution to this and will if you will give me a hand will have a look at it John Locke’s please what you’ve got here is basically a pipe Network these are a series of vertical pipes go down. Into the riverbed the little holes in the side of them we connect them up to a high pressure pump because it wouldn’t be this but it would be a big bump. In this pump what we’ve got is a watery grout it’s just cement and water. And when that cemented the grout goes hard it creates an impermeable barrier just this time it in the soil so we’ll have a go our high pressure pump.
So if I squeeze them really hard there we are and pretty much straight away you can see the ground coming out and running through the soil and spreading out which is exactly what we want to of course you can see in some areas. It goes a long way in other areas it doesn’t get through that means that the soil is denser and less permeable there but that’s fine because what you do is you drill more holes down into the areas and you squirt more grout and you basically you keep going until you’ve got a continuous curtain underneath the down and then we are so we have our impermeable down on top of the river bed. And we’ve created a concrete dam underneath the riverbed to create an impermeable concrete curtain beneath the Three Gorges Dam engineers drive 100 kilometers of tubing down into the granite bedroom. Then they pump 200,000 cubic meters of grout which is squeezed into the fishes in the rock as the ground hardens. It turns the leaky rock into a solid waterproof base for their down now the Chinese engineers can be confident that the Yangtze will not undermined that basically the dam holds back a large volume of the water during the flood, it can hold back about 22 billion cubic meters of water and then its release in a controlled way through this system of 46 go away gates.
These shows that you can see below me here the design of a spillway like this has the deal with the force of the water as the drops over a hundred meters in this case here and then achieves huge velocity at the bottom of the Damned to deflect the force of the water crashing down the Chinese use technology similar to the Grand Coulee. As the water levels rise engineers open a series of gates to drain the flood water from the reservoir but if the water fell straight down that could undermine the foundations of the Damned so the engineers fit the spillway with concrete shoots. Unlike the Grand Coulee ramp which is underwater the three gorgeous shoots hold the water into the air once airborne the water breaks up into small droplets and loses much of its destructive energy. It lands over a hundred meters downstream where it can’t do any damage so now when they open their spillway gates the Chinese have nothing to worry about at China’s Three Gorges. There the engineers also face a major traffic problem their damn said some one of the busiest rivers in Asia the Yangtze is a really important waterway for navigation traffic in China. Lead all the way from Shanghai the coast up to a chain or a to Chongqing it’s been carrying about 18 million tons of freight a year getting about a hundred and seventy ships a day over a dam. That’s more than a hundred meters high is a tall order for the engineers the fitting the biggest damn on earth the Chinese solve it by building the biggest shift lock on it ships into the lock at the bottom of the Damn. The gates closed water floods in and lift the ship’s up to the next book ships must go through five tiers of locks to get to the top which can take up to four hours this is fine for cargo ships but for the many passenger boats operating on the Yangtze it’s just too slow to provide a more efficient transit opportunity for passenger traffic. They’ve built this ship lift system. Which will allow boats to go through in about 36 minutes unlike the ship lifted because I asked the one of the Three Gorges will lift ship straight up like an elevator and the secret of its success lie hidden in its concrete wolves the engineers will fit a series of massive counterweights? That will do most of the lifting 16 1010 concrete blocks will be connected by cables to the steel. Through that will carry the ship and the water it floats as the counterweights draw they will host the trough upwards and lift the ship to the top this ship lift here is a hundred and thirteen meters height. And can handle vessels up to 3,000 tons we’ll make it the largest in the world and twice the size of the one that question asked certainly when you look at the structure. Now it’s kind of ways to go in terms of construction have you finished your 2015 but it’s clearly a huge and it’s another very impressive achievement underway.
The Three Gorges Dam produces more power than any other but that’s not the main reason it with built the Yangtze river is notorious for its really severe flooding over the last 2,000 years has been about one major flood every 10 years in 1931. There was a really bad one killed about a hundred and thirty-five thousand people destroyed almost 2 million homes and so that this is the main reason why they built the Three Gorges Dam is to control this terrible flooding problem the damn blocks the path of the destructive flood water. The water is stored in its reservoir and is then released in a controlled way but managing flood water can also have serious environmental side effects. As recent history has shown in nineteen seventy Egyptian engineers build the as one high dam across the river Nile to control flooding but soon farmers downstream notice that their harvests are beginning to fail the soil becomes so barren the farmers need millions of tons of fertilizer every year to nourish their crops their land has suffered.
It has been deprived of floodwater which carries with it the vital building blocks of life chemist Dr. Andrew demonstrates so we have here are clean rainwater which has been falling we adding to it some good quality topsoil we then add some animal excrement we have some slaves shells essentially made of calcium carbonate then we have some dry leaves Clark vegetation. And of course fish as the storm proceeds as the water starts to flow rapidly all of these ingredients get mashed up in the hugely violent storm waters. Which occur so we have it a veritable cocktail of Mother Nature’s most important plant nutrients nitrogen phosphorus calcium magnesium and potassium but if flood water stops flowing these nutritious particles of silt? Will begin to settle this is a big problem especially in the biggest damn in the world the flow of precious Yangtze silt is blocked by the dam and trapped in the slow-moving water reservoir it rapidly sinks to the bottom. Where it builds up sorting problem on the Yangtze is a huge problem total amount coming down it’s about 500 million tons per year. Which equates to about one kilometer that’s enough to fill big sports stadiums hundreds of time it’s a huge episode if this silt remains trapped behind the damn it would mean that farmer’s fishermen and Wildlife would be deprived of nutrients in the water for hundreds of miles downstream? And the tons of settled silt sediment could build up in the reservoir and threatened the dam itself basically sediment falling into the reservoir would reduce the capacity the reservoir capacity and would eventually perhaps interfere with the ability to run the turbines. If it was came up cleverly the Chinese engineers exploit the power of flood water to flush the sediment out of the reservoir and send it down stream they installed sluice gates deep inside the dam. Each gate weighs as much as a bus and needs a powerful hydraulic piston to lift it up when the operators open the gates flood water rushes over the trap sediment and sweeps it through the dam.
This way the Chinese authorities hope that it will be at least another 100 years before the build-up of sediment effects power production at the time but even the clever purging system cannot carry all the sediment across the dam scientific estimates. On how much sediment remains behind vary from as little as thirty percent to as much as sixty percent the Chinese authorities believe that this is a price worth pain they are convinced that the benefits of the Dam. Such as clean energy and flood control far outweigh its significant draw backs as the Three Gorgeous project draws to completion its scale is breathtaking even with some of its turbine. Still to be switched on it produces more power than any other damn in the world standing on the shoulders of historic engineering giants. The Three Gorges really is the ultimate hydroelectric dam until someone builds an even bigger.