Detail Explanation of Three Gorges Dam and its World largest hydro power Generation Units
Basic information of Three Gorges Dam
from the waters of the Yangtze River in 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 40,000 workers over 17 years to build when it fully comes online this one dam 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 of dam engineering
China is one of the fastest-growing economies on earth to fuel the need of its ever-accelerating industry the nation needs more power much of this will be provided by an enormous dam spanning the mighty Yangtze River in central China called the Three Gorges Dam our eyes have been granted privileged access to view 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 dam a huge mass of water actually slowed down the speed of the Earth's rotation by a fraction
Construction Detail of Three Gorges Dam
Three Gorges Dam is the biggest hydroelectric project in the world this dam used 28 million cubic meters of concrete may be one way to look at it is to say so solid Pieper concrete a meter diameter right around the world a lot of Concord 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 char wood has been working on the dam since 2003 and is still impressed by its scale we're in one of the three very large powerhouses of the Three Gorges project in In this 700-meter long room here you can see 14 of their large turbine generators then beyond this one kilometer away is the second powerhouse and then beyond that one has yet another powerhouse which would be underground in the rock about the far side of the river each one of these generators cost about 50 million dollars give you an idea of the scale of this project Deb Dan Dam had one generator three gorges has 32 together they produce five million times more power than deadly 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 sixty stories above the riverbed the water is channeled down gigantic concrete tubes towards the generators
here the torrent of water hits the turbines and makes them spent this motion is in turn transferred to the rotor of the generator this is fitted with massive magnets which move 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 inside Peru in Brazil and of course it's only the first of a whole series of mega dads that are under construction here in China the Yangtze River is over six thousand kilometres long and in places several kilometres wide the biggest river in China it presents enormous logistical challenges to the damage nears as the Yangtze rises behind the Three Gorges Dam 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 displaced citizens to live in then the engineers can begin to down the river we're standing here amongst some of the rocks and these precast concrete blocks that were used to create the coffer dams to control the river during the construction of the three gorges project controlling the river to 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 claimed that this was the largest and most difficult diversion ever undertaken for a 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 axial whilst leaving a channel open for the rest of the river to flow through they build the first two sections of the main dam on the dry riverbed then they dumped tons of earth into the river and on top of it build another coffer dam this time from concrete with the river held in check behind it they can finally build the last section of the dam then they must remove the coffer dams so that water can flow through the turbines of the main dam having built such substantial confidence 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 excavator equipment relatively conventional but in the final stage where they had a solid concrete wall to remove this required some serious innovation unlike the coffer dam in Mirage 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 6th 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 picture the thickness of the concrete at the base of the dam
Hydro electric power generation plant
the hydrant 180
meters and it's 2 kilometres long
so it's a colossal amount of
concrete Three Gorges uses ten times
more concrete than the Hoover Dam so
the engineers have to pull out all the
stops to keep their damn cool they
basically used everything in the book
they cooled the aggregates and the materials
the sands 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 here because of the issue of 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 fog 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 from cracking
will count for nothing if the dam
is built on weak foundations a civil engineer
at McCann explains well we can make
the dam completely impermeable it's rather
harder for us to make the riverbed
impermeable now of course once the
water is up behind the dam here there's
a huge pressure pushing it this way
and whilst the dam won't let 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 we'll give me a hand
so I'll have a look at it John blocks
please what you've got here is
basically a pipe Network these are a series
of vertical pipes go down into the
riverbed with little holes in the side
of them and we connect them up to a high-pressure pump of course it wouldn't be
this baby big pump in this pump what we've got is a watery grout it's just cement
and water and when that cement and the grout goes hard it creates an the impermeable barrier just this time it’s in the soil so we'll have a go here
‘sour high-pressure pump squeeze that really hither we are and pretty much
straightaway you can see the grout coming out and running through the soil and
spreading out which is exactly what we want to see of course and you can see In some areas it goes a long way and in other areas, it doesn't get through that
means that the soil is denser and less Mabel there but that's fine because what
you do is you drill more holes down into the areas here and you squirt more grout
and you basically you keep going until you’ve got a continuous curtain
underneath the dam and there we are so we have our impermeable dam on top of
the riverbed 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 bedrock then they pump 200,000
cubic meters of grout into the tubes which is squeezed into the fissures in the
rock as the grout hardens it turns the leaky rock into a solid waterproof base
for their damp now the Chinese engineers can be confident that the Yangtze will
not undermine their Dam basically the dam holds back a large volume of the
water during the flood period here it can hold back about a 22billion cubic
meters of water and then it’s released in a controlled way through this
system of 46 spillway gates and these chutes that you can see below me here the
design of a spillway like this has to 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 dam 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 floodwater from the reservoir
but if the water fell straight down that could undermine the foundations of the
dam so the engineers fit the spillway with concrete shoes unlike the Grand
Coulee ramp which is underwater the three gorges chutes 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 damages now when they open their spillway gates the Chinese have nothing to
worry about at China's Three Gorges them the engineers also face a major traffic
problem their dam set someone of the busiest rivers in Asia the Yangtze is a
really important waterway for navigation traffic in China lead all the way from
shanghaied the coast up to Yichang or to Chongqing it’s been carrying about 18
million tons of freight per year getting about a hundred and seventy ships a
day over Adam that's more than a hundred meters high is a tall order for the engineers
befitting the biggest dam on earth the Chinese solve it by building the biggest
ship block on earth ships enter the lock at the bottom of the dam the gates
closed water floods in and lifts the ships up to the next blockships 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 The Yangtze it's just too slow to provide a more efficient transit opportunity for
passenger traffic they’ve built this ship lift system here which will allow
boats to go through in about 36 minutes unlike the ship lift at cruising I asked
the one of the Three Gorges will lift ships straight up like an elevator and
the secret of its success will lie hidden in its concrete walls the engineers
will fit a series of massive counterweights that will do most of the lifting
sixteen 1000 ton concrete blocks will be connected by cables to the steel trough
that will carry the ship and the water it floats in as the counterweights drop them
will host the trough upwards and lift the ship to the top[Music]this ship lived
here is 113 meters height and can handle vessels up to 3000tonnes will make it
the largest of the world and twice the size of the one that crushed me ask
certainly, when you look at the structure now it's a lot of ways to go in terms
of construction won't be finished till 2015 but it's it's clearly huge and it's
of another very impressive achievement underway here the three gorges dam
produces more power than any other but that's not the main reason it was built
the Yangtze River is notorious for its really severe flooding over the last
2,000 years has been about one major flood every ten years in 1931there was a
really bad one killed about a hundred and thirty-five thousand people destroyed
almost two million homes and so this is the main reason why they’ve built the
Three Gorges Dam is to control this terrible flooding problem the dam blocks
the path of the destructive floodwater the water is stored in its reservoir and
is then released in a controlled way but managing floodwater can also have
serious environmental side effects as recent history as shown in 1970 Egyptian
engineers build the Aswan High Dam across the River Nile to control flooding[Music]but
soon farmers downstream noticed that their harvests are beginning to fail their
soil becomes so barren that the farmers need millions of tons of fertilizer
every year to nourish their crops their land has suffered because it has been
deprived of floodwater which carries with it the vital building blocks of life
chemist dr. Andrew Schindler who demonstrates so we have here our clean
rainwater which has been falling we're adding to it some good quality topsoil
we then add some animal excrement we have some snail shells essentially made of
calcium carbonate then we have some dried leaves plant vegetation here 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 here 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 dam in the thiolate 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 the total amount coming down is about
500 million tons per year which equate to about a one-kilometer cube perhaps
enough to fill big sports stadiums hundreds of times it's a huge amount of silt
if this silt remains trapped behind the dam it would mean that farmers fishermen
and wildlife would be deprived of nutrients in the water for hundreds of miles
downstream and the tons of settled silt or sediment could build up in the
reservoir and threaten the dam itself basically sediment falling into the reservoir here would reduce the capacity the reservoir capacity and would
eventually, perhaps interfere with the ability to run the turbines if he was
came up cleverly the Chinese engineers exploit the power of floodwater to
flush the sediment out of the reservoir and send it downstream they installed
sluice gates deep inside the dam each gate weighs as much as abuse and needs a
powerful hydraulic piston to lift it up when the operators open the gates floodwater
rushes over the tracks 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 affects power production at the dam 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 30 percent to as much as 60percent
the Chinese authorities believe that this is a price worth paying they are
convinced that the benefits of the dam such as clean energy and flood control
far outweigh its significant drawback as the Three Gorges project draws to
completion its scale is breath-taking with some of its turbines still tube switched
on it produces more power than any other dam 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 one
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