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Monsters of concrete, gigantic artificial lakes.
Explore the engineering marvels of French dams like Tinia, La Rance, and Roselend, showcasing innovative hydroelectric power solutions.
Key Takeaways
- French dams are engineering masterpieces combining innovative design and massive scale to harness hydroelectric power.
- Mountainous terrain requires unique logistical solutions, such as cable cars and on-site concrete production.
- Vault-shaped dams like Tignes use water pressure to enhance structural stability rather than resist it passively.
- Continuous monitoring and maintenance are critical due to natural movements and wear in dam structures and turbines.
- André Coyne’s contributions significantly shaped modern French dam engineering and hydroelectric capacity.
Summary
- The video highlights monumental French dams such as Tinia, La Rance, and Roselend, showcasing their unique engineering and hydroelectric capabilities.
- Tinia is noted as the biggest dam in Europe and the third highest worldwide at its time, holding the equivalent of 100,000 Olympic pools of water.
- La Rance is the world's first tidal barrage producing electricity entirely from tidal forces, located in Brittany.
- Roselend holds a record for concrete use and generates power comparable to a nuclear reactor through its massive turbines.
- France has over 650 dams, with a long history of engineering expertise dating back to the 18th century.
- The construction of dams in mountainous terrain presents logistical challenges, solved by innovations like a 21 km cable car for material transport.
- The Tignes dam uses a vault design that anchors itself into the mountain, increasing stability under water pressure.
- Engineer André Coyne played a key role in designing over 70 dams, including Tignes and Serre-Ponçon, Europe's largest hydroelectric dam by capacity.
- The dams incorporate drainage galleries and tunnels to monitor stability and relieve pressure, ensuring long-term safety.
- The video also covers the precision engineering of turbines and the challenges of maintenance in such large-scale hydroelectric plants.
Full Transcript — Download SRT & Markdown
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Power plants dug into the mountains.
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Or buried in the sea, hydroelectric dams beyond belief.
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Like the most famous one, at Tinia.
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The biggest dam in Europe and the third highest in the world at the time, it's a monumental work.
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Behind this wall, there's the equivalent of 100,000 Olympic swimming pools.
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To resist the force of the water, the dam is designed with dozens of micro-foots.
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In Brittany, there's La Rance.
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No one imagines that hidden under this bridge is the first barrage in the world to produce electricity entirely thanks to tides, which are among the highest on the planet.
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If La Rance is a titan of the seas, Roselend is its equivalent in the mountains.
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It holds the absolute record in terms of concrete.
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An exceptional stratagem makes it as powerful as a nuclear reactor.
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The water that rushes down from the dam drives wheels weighing more than 20 tons.
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Tinia, La Rance, and Roselend.
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Three dams, three masterpieces of civil engineering.
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France has a lot of dams.
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There are more than 650 of them.
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Since the 18th century, French engineers have amassed a unique know-how in the field.
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Overcoming new challenges each time.
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Such as filling the dam's lakes without disfiguring the landscape.
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To tap water resources and rivers to feed our big dam, we dug 1,500 kilometers of tunnels.
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That's one and a half times the length of France.
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Once the wall is built, a gallery will make the water rush almost vertically towards a hydroelectric plant.
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Inside, giant turbines are driven by the speed of the water.
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The jet arrives at 500 kilometers per hour.
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The moving parts of the turbine need to be perfectly assembled.
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They're adjusted to a tenth of a millimeter, with parts weighing up to 100 tons.
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It's a power generating performance in the size XXL.
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In 1952, Tinia beats all records.
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Never before in France has a work required so much material to achieve its intended dimensions.
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The dam holds back a phenomenal amount of water.
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When the gates open, it's conducted into an underground gallery.
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At the plant, it will drive the turbines and thus produce electricity.
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After World War II, France has an ever-growing need for energy.
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The powers that be focus on the country's environmental potential.
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The idea was, let's use what we have, our valleys and rivers.
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After scanning the countryside for possible sites, the research departments are unanimous.
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One region lends itself to the project just perfectly.
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It's Savoy, and particularly the mountain area southwest of the Mont Blanc massif.
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It had been identified between the walls as an ideal site for a water reservoir.
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In the Chevreul Valley, there is a river, the Isère.
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If a wall could stop its course, it could be used to fill the lake behind the dam.
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But there's another, even more potent source, albeit more than 2,000 meters high.
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The main source of the reservoir is melting snow.
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This combined water supply can be used to create an artificial lake behind the future wall.
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And there's another asset.
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At the end of the Chevreul Valley, the mountains form a natural lock.
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Yet, there's a problem.
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As with all construction sites in mountainous terrain, access is limited.
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The roads are impassable for huge trucks, cranes and cumbersome machines.
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Tinia is in the middle of nowhere.
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Bringing cement and materials poses enormous logistical problems.
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So, how to get tons of material up to more than 1,600 meters?
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Yet, there's a solution to everything.
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They built a cable car line between Bourg-Saint-Maurice and Tignes.
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That's 21 kilometers.
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To lift the cement that arrived at the nearest train station.
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Nobody had ever built such a means of transport over a distance like that.
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The cement is stored in huge silos of 4,000 tons.
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To transport the rocks for the concrete, giant trucks are brought over from the United States, the Euclids.
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They deliver the raw material from a quarry, three kilometers away, where the blocks are extracted with a view to producing concrete on the spot.
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They used more than 16 tons of explosives to extract 106,000 tons of limestone for the Tignes dam.
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At an extraction rate of 400 tons per hour, the pace of the site is exceptional.
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However, it's dictated by the weather in the mountains.
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It's impossible to work in all seasons.
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They only had 140 to 150 days a year to pour concrete.
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So they had to do as much as possible in that time.
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To compensate for the delays due to snow and cold, up to 5,000 workers are brought in during the summer of 1949.
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It's a record in Europe.
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The dam proper requires gigantic foundations 20 meters deep.
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The equivalent of an eight-story building.
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Once the concrete is injected, it will cling to the hard rock below.
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Then the wall is raised block by block up to its planned height of 180 meters.
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Four supports are added on the outside of the curve that faces the valley.
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Geological study of the parts of the massif which have to resist the forces on the sides is fundamental.
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If it's faulty, the dam will collapse.
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The foundations of the dam, as well as its links on both sides, must be solidly anchored.
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As the pressure exerted by the mass of water will be immense.
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The lake of the Tignes dam holds 235 million liters of water.
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To counter this monumental thrust, the engineers opt for a particular design.
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It differs from conventional dams where material is piled up into a kind of artificial mountain.
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The Tignes dam is shaped like a vault.
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Thus, the more pressure the water exerts, the more the dam anchors itself in the mountain.
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It's pushed into the rock.
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Yet, there's another way to relieve the pressure on the dam.
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André Coyne is an engineer of bridges and roads.
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One of the masterminds behind the Tignes dam was André Coyne, who holds a special place in the history of French dams since he designed more than 70.
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He also planned another exceptional dam in the 1950s.
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Serre-Ponçon in the Alps.
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The biggest dam in Europe in terms of hydroelectric capacity.
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Coyne's ploy to keep the wall from giving way at Tignes is to relieve the pressure by letting water seep out.
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At the foot of the dam, the builders dig openings to let small quantities of water through.
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The drains are between 20 and 40 meters long.
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As the thickness of the dam differs along its height.
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At the road, it's 10 meters, then it's widening till on its base, it's 43 meters thick.
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So it's a real pyramid of concrete that's built between 1946 and 1952.
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And like its Egyptian ancestors, the dam also contains hidden tunnels.
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There's an upper gallery, two intermediate galleries, and a lower gallery.
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They're accessible only by the staff operating the dam.
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Allowing them to check for any signs of water infiltration and whether the dam is still stable on its supports.
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Yet another phenomenon is scrutinized with even more attention.
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The colossus lives, breathes, and moves permanently.
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The expansion of the concrete in summer, as well as the retraction at sub-zero temperatures, have an influence on the dam.
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These movements are anything but negligible.
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When we monitor the lead weight several dozen meters below where it's suspended, we can see that the dam moves several centimeters.
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So the dam is solid, the turbines, however, are more fragile.
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Exchanging a part is a long and complex process.
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It's necessary to raise the cover above the unit and to remove the elements one by one.
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An operation which takes several months.
Topics:French damshydroelectric powerTinia damLa Rance tidal barrageRoselend damAndré Coynecivil engineeringmountain damshydropower turbinesdam construction logistics
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