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00:00Picture a mountainous landscape covered with winding roads.
00:04It looks beautiful, but traveling along such routes takes far too much time.
00:09Do you know what they did in China, in the province of Guizhou?
00:13They simply blew up a massive mountain range and built a bridge.
00:17But this is not just a bridge.
00:19It's a true marvel of engineering.
00:22So let's take a drive across it.
00:25Locals say there's not a single flat piece of land in Guizhou.
00:29More than 90% of the region consists of mountains and hills.
00:33All of this is beautiful and picturesque, but it creates serious logistical problems.
00:38It's one thing to come here as a tourist and enjoy the views,
00:42and quite another to live here and drive to work every day.
00:46People had to take long routes along winding roads and steep slopes.
00:50A car trip could take around 2 hours.
00:53But engineers built a bridge that reduced this travel time to just 120 seconds.
01:00They literally split a mountain in half, creating a V-shaped cut through the rock.
01:05Then they laid a road through the mountain range and led it onto a high bridge spanning a massive canyon.
01:13The entire route is constructed so precisely that drivers barely notice the moment when the road through the mountain ends
01:20and the bridge begins.
01:22It's total length is 9,500 feet.
01:25That's roughly one-third of the height of Mount Everest.
01:29But the length is not as impressive as the height.
01:32The Huajang Canyon Bridge is considered the highest bridge in the world.
01:37Just imagine driving at a height of about 2,000 feet above the ground.
01:41That's almost six times higher than the Statue of Liberty.
01:45But this isn't just a road.
01:47It's also a major tourist attraction.
01:49So what can the tourists do on the bridge?
01:52Just walk and enjoy the view?
01:54Well, that's only a small part.
01:56There's a panoramic glass elevator that connects the highway with the base of the canyon.
02:02You can have lunch in a special two-story cafe located inside one of the bridge towers, offering an incredible
02:09view.
02:10There's an artificial waterfall and a glass pedestrian walkway in the lower part of the parking area.
02:16But the coolest part is the extreme activities, like a platform for bungee jumping.
02:22You hook yourself to a bungee cord and leap into the abyss.
02:26Ah, no thanks.
02:28And for true adrenaline lovers, professional base jumping competitions are held here too.
02:34You leap from an enormous height with a parachute or a wingsuit and soar through the canyon at an incredible
02:40speed, like a hawk.
02:43It sounds amazing, and you probably already want to come here and post a few photos.
02:48But how did they build it?
02:50And how safe is it?
02:52From the outside, it looks like a thin metal strip suspended at a terrifying height.
02:58The entire structure is supported by steel cables and panels, with a total weight of about 22,000 tons.
03:06In fact, the amount of steel used to build this bridge is three times greater than that used to construct
03:11the Eiffel Tower.
03:12The main cables of the bridge are anchored directly into solid rock, so the bridge won't collapse.
03:18But if something does go wrong, the builders will know immediately.
03:23Fiber-optic sensors are installed within the cables.
03:26In real time, they monitor tension and expansion in the steel.
03:30This means the bridge is under constant observation.
03:34If strong winds or other factors cause any issues, engineers will detect them in advance and fix the problem.
03:40But the most impressive part is that during construction, scientists took all turbulence zones into account.
03:48How did they manage that?
03:50Well, there's a phenomenon called the Venturi effect.
03:53When wind passes through a narrow space, such as a canyon or tunnel, it accelerates.
03:59In Guizhou province, this effect is very common.
04:03Wind gusts in the Wajang Canyon can reach speeds comparable to a high-speed train.
04:08So, how did they manage to build a bridge under these conditions?
04:13Well, before construction began, engineers created a mock-up and tested it in a wind tunnel.
04:19Using special instruments, they studied wind directions and compiled a unique airflow map
04:25that allowed them to predict all turbulence zones.
04:28With this information, they moved on to the actual construction.
04:33Now, let's see another impressive bridge in China.
04:36This is the Sea-Doo River Bridge, which spans the Sea-Doo River, obviously.
04:41It was opened in 2009 and became part of an expanding highway system that connects the entire country.
04:48Of course, it's not as long or as tall as the Wajang Bridge.
04:52It's supported by two H-shaped towers located on both sides of the roadway.
04:57Because of the suspension cables that dip down and rise again in the middle, the bridge looks, well, fragile.
05:04But don't judge by appearances.
05:07Engineers designed this structure to withstand a load of more than 43 million tons.
05:13That's equivalent to the weight of 430 massive aircraft carriers.
05:17So, driving across it is completely safe.
05:20But do you know what the coolest part of this bridge is?
05:24To stretch the first pilot cable from one side to the other,
05:27across a distance of more than 5,000 feet, builders used a rocket.
05:33You know those heist movies where the thieves release a grappling hook or a harpoon to cross from one building
05:39to another?
05:40The workers did something like that here.
05:42You probably had no idea that bridges could be built this way.
05:47Okay, let's now move from high-tech giant bridges to something much simpler and more dangerous.
05:54Think back to cartoons and movies about Mowgli and Tarzan.
05:59Remember how they swung through dense jungles, climbing vines and trees?
06:04Well, you can relive that experience if you travel to Ghana, where the Khakum Canopy Walk is located.
06:11So, this is a series of rope bridges right inside a real jungle.
06:15Two Canadian engineers and several locals created this attraction in 1995 to draw tourists.
06:22At first glance, these bridges look like the vine and wood rope bridges you've seen in adventure movies.
06:27However, they are reinforced with steel cables, aluminum, and wooden planks.
06:32And they also have protective mesh barriers to present accidental falls.
06:37Good thing!
06:39The bridges hang from trees at a height of more than 130 feet.
06:44And their total length is about 1,000 feet.
06:46So, you can truly feel like Tarzan.
06:50Meanwhile, the bridge at El Caminito del Rey in Malaga, Spain, runs between two cliffs.
06:57Only 3 feet wide, it's suspended 328 feet above the river.
07:03It's a very narrow path.
07:05You'll probably feel dizzy during the crossing.
07:07But, don't worry, the bridge is equipped with high railings.
07:11It was originally built so workers at hydroelectric power stations could cross the mountainous terrain.
07:17Eventually, it became a local landmark.
07:20A small but incredibly cozy and picturesque bridge.
07:23You look at it, and you immediately want to walk across this stunning path.
07:28Me?
07:28Not so much.
07:29I don't like heights.
07:31Well, we started this video with one of the most technologically advanced bridges in the world.
07:36Let's finish with one of the most dangerous and extreme.
07:40Oh, goody.
07:41It's called the Husseini Suspension Bridge and is located in the Gilgit-Baltistan region in northern Pakistan.
07:48In this area, residents were cut off from the rest of the country because of the mountainous terrain and lack
07:54of roads.
07:56Wealthier locals could travel here by plane, but for everyone else, only pedestrian crossings were available.
08:03Then a highway was built here, along with several fragile wooden bridges.
08:08And the most famous of them is the Husseini Bridge.
08:12If you find yourself at the very beginning of it, you will probably think twice before crossing this path.
08:19Now it looks much better.
08:21But in the past, this bridge had many planks missing.
08:24And strong winds shook the structure from side to side.
08:28There were no safety nets or high railings.
08:31In 2011, the bridge was destroyed by monsoon rains.
08:35After that, it was completely reconstructed.
08:38Now it consists of steel cables and sturdy wooden planks.
08:42And nearby, there are ziplining and sky-cycling stations.
08:46It's become a popular tourist attraction.
08:49So, if you enjoy testing your nerves and are a fan of Indiana Jones, you will definitely like this place.
08:57Me, I'll just watch you.
09:00To build an underwater structure, you'll need some interesting engineering.
09:04A large bridge over a river or bay has its foundation rooted underwater.
09:08It's even more complicated with undersea tunnels.
09:12Underwater construction is challenging.
09:14Engineers need to deal with water pressure and corrosion from saltwater.
09:17There's also a problem of finding suitable materials.
09:21The most typical of them are concrete, steel, and acrylic glass.
09:25Concrete doesn't care about water currents and doesn't get damaged by saltwater.
09:29Steel provides underwater constructions with a strong structure.
09:33And acrylic glass is tough, long-lasting, and resistant to sunlight.
09:37It's also transparent.
09:38That's why it's often used to make windows in underwater buildings.
09:42Anyway, when the water is shallow, it's not that hard to build something there.
09:46However, constructors create a temporary foundation.
09:49Then, on top of it, they build several piers supporting the upper structure.
09:53But if the waters are deep, engineers have to use other methods.
09:57Depending on which one they choose, water is either extracted or diverted during the construction process.
10:03One such method involves using a set of large driven piles.
10:07Those are long, thin columns made mostly of steel.
10:09But their interior is partially hollow.
10:12With the help of a huge hammer, they get driven into the waterbed, like nails are driven into a piece
10:17of wood.
10:18After that, these steel columns get filled with concrete through a special tube.
10:22The concrete displaces the water that was in the pile before.
10:26Concrete has the ability to set, even when it's surrounded by water.
10:30That's why driven piles eventually turn into a stable foundation for overwater and underwater constructions.
10:36Driven piles are a very cost-effective way of building something that has to be fixed in place.
10:41They prevent things from being moved by the water current.
10:44Another way to build underwater structures is coffer dams.
10:47They are built temporarily and allow workers to create a dry space for the construction.
10:52The water gets pumped out of this enclosure, and the coffer dam works like a dam.
10:57A completed coffer dam looks like a massive pit with high walls surrounded by water.
11:02Coffer dams are made of rocks, steel, and even dirt.
11:05These constructions can be built fast and removed even faster.
11:09But the process of putting up a coffer dam is complicated and challenging for engineers.
11:14They have to make sure the structure won't flood or collapse.
11:17The simplest way to build a coffer dam is to pile up loads of dirt.
11:21But in this case, workers usually have to somehow make the construction stronger.
11:25It helps to protect it from the damage caused by water.
11:28Once the coffer dam is ready, pumps extract the water from its interior.
11:32Sometimes, it's too expensive to build a very deep and strong coffer dam.
11:37In this case, constructors use several powerful pumps that get rid of excess water when it seeps through the coffer
11:42dam walls.
11:43If a coffer dam starts to fail, this process is slow and, luckily, predictable.
11:48On the construction site, there are not only main but also backup pumps.
11:53In case of emergency, they can kick into overdrive.
11:56Then, the water is kept out for the time the personnel needs to evacuate.
12:00Coffer dams are most often used during the construction of dams and bridges.
12:04But when a large ship, like a modern cruise liner, needs to be repaired, engineers use coffer dams too.
12:11Such vessels are too massive to be hauled ashore.
12:13And a coffer dam makes a perfect dry lock.
12:16The ship gets isolated from the water, and mechanics can repair it wherever it sits.
12:20Also, when a cruise ship needs to be expanded, engineers construct a coffer dam around it.
12:26Then they pump out all the water from the inside, creating a dry working place.
12:31The ship gets cut into two parts, and the process of its lengthening begins.
12:36There are several main types of coffer dams.
12:38Braced, cellular, rock-filled, or earthen.
12:41For each of them, engineers need to figure out the best depth at which the wall should be put into
12:46the ground.
12:47It depends on the type of soil and the water reservoir itself.
12:51Braced coffer dams are mostly used during shallow water construction.
12:55Such a structure is actually a wall of sheet piles.
12:58Those are parts with interlocking edges.
13:00Usually, they're made of steel, but the material can also be reinforced concrete or timber.
13:06Sheet piles create something like a box around the needed area.
13:10Cellular coffer dams are also made of sheet piles.
13:13But in this case, the piles have a special shape.
13:16After being connected, they form cells that get filled with soil or clay.
13:20The cells, in turn, create a watertight wall.
13:23Thanks to its structure, it's exceptionally stable.
13:26Rock-filled coffer dams are used when there's a lot of rock at the construction site.
13:31They're built over the soil.
13:32This prevents the water from seeping into the coffer dam, and the rocks serve as reinforcement.
13:38Earthen coffer dams are built in areas where the water is less than 10 feet deep.
13:42They're created from the materials that are at hand—clay, sand, and even soil.
13:47There are also single-walled and double-walled coffer dams.
13:51The first type is used when the area of the construction isn't large and the depth is more than 20
13:56feet.
13:56Such coffer dams are typically necessary for building bridges.
14:00Timber or wooden sheets are put into the sea or riverbed.
14:03After that, iron or steel sheets are added on the inside.
14:07On both sides of the wall, workers place half-filled bags of sand.
14:11Finally, the water gets pumped out and the coffer dam is ready for use.
14:15The double-walled coffer dam is used for large construction areas and when the water is very deep.
14:21Such construction sites need more powerful supports.
14:24This stronger coffer dam has two walls, which provides it with extra stability.
14:29Two piles get pushed into the waterbed with some space in between.
14:32The deeper it is, the bigger the space between the walls.
14:35Then they get attached to each other.
14:38After that, this space gets filled with soil.
14:41Coffer dams aren't cheap.
14:42This means that if one is used for a project, there are no other available options.
14:47For example, it's the best way to construct permanent dams.
14:51When the Hoover Dam was built, several coffer dams were put up to divert the water from the Colorado River.
14:56As soon as the project is finished, the water is pumped back into the coffer dam.
15:00And its walls, whatever they are, get removed.
15:04One more way of underwater construction is caissons.
15:07They are watertight structures that are put into the water.
15:10Even open, they remain dry inside.
15:13Workers can keep digging down until they reach some solid surface.
15:16That's where the caisson will be placed upon.
15:18What's so different about caissons is that they eventually become parts of the foundation for, let's say, a bridge or
15:25a dam.
15:26And even though you might not think of a bridge or a dam as an underwater construction, most of their
15:31crucial elements are underwater.
15:33For example, a large bridge wouldn't be able to hold its weight without massive supporting towers.
15:38And they stand in the water.
15:39There are several types of caissons.
15:42Open, pneumatic, and box.
15:44Open caissons have no bottom.
15:46They're actually just vertical walls that allow builders to dig at the bottom of them.
15:50Pneumatic caissons keep the water from seeping through by using compressed air.
15:55This helps to maintain equal pressure inside and outside the construction.
15:59When workers dig out some materials, these get sent up through a special muck tube.
16:04When the caisson reaches the bedrock, workers fill it with concrete.
16:07Unlike others, a box caisson has a floor.
16:11And workers lower it onto a foundation that is constructed in advance.
16:15During the construction of the Brooklyn Bridge, engineers used two massive caissons.
16:20Thanks to them, they reached the bedrock and created the foundation for the towers of the bridge.
16:25And then, there's also off-site construction.
16:28That's when things are not only built, but also assembled away from the site.
16:32In this case, engineers often use modular construction.
16:35That's when factory-produced building units are delivered to the site.
16:39There, they get assembled, like a giant Lego set.
16:43Structures are then usually floated to the site on huge barges.
16:46Or they get towed there.
16:48After that, they're lowered in place.
16:50Some sink under their own weight.
16:52Others can only reach the seafloor after getting loaded with additional weights.
16:56This method of construction is rather expensive.
16:59And still, it's much more cost-effective than building right underwater.
17:02The latter needs skilled engineers and unique tools.
17:06And don't forget about the risks.
17:08But what about underwater tunnels?
17:09How on earth are they constructed?
17:11Modern tunnels are usually built with the help of massive tunnel boring machines.
17:16They even have a nickname.
17:17Moles.
17:18Even though such a mechanism has an exorbitant price, several million dollars,
17:23it needs little time to create a long tunnel.
17:25The machine moves forward very slowly.
17:28It has a special circular plate with rotating disc cutters.
17:31They can easily chew through solid rock.
17:34The rock is then dropped onto an outboard conveyor belt.
17:37Another mechanism uses this rock to construct the tunnel's lining in the mole's wake.
17:42This way, the mole not only excavates the tunnel,
17:46but also reinforces the walls that will later support it.
17:49This method, and 11 huge tunnel boring machines,
17:52was used to build the 32-mile-long channel tunnel.
17:56And the whole process took only three years.
17:58Cut and cover is another method of creating a tunnel underwater.
18:02First, workers dig a trench in the ocean floor or riverbed.
18:06Then, they put concrete or steel tubes there, made in advance.
18:10After the tubes get covered with a thick layer of rock,
18:13the sections are connected.
18:14All workers have to do is pump out the water.
18:16That's how the Ted Williams Tunnel, connecting Logan Airport with South Boston, was built.
18:22There, they used 12 enormous steel tubes, more than 300 feet each.
18:27And the tubes contained already fully constructed roads.
18:31That's it for today.
18:32So, hey, if you pacified your curiosity,
18:35then give the video a like and share it with your friends.
18:37Or, if you want more, just click on these videos and stay on the bright side.
18:41So, let's get started.
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