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How Japan Built the Impossible 400 km Great Wall that You've Never Heard Of — Transcript

by NextGen Manufacturing · 2,008 words · 414 segments · language en · Watch on YouTube

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0:05Japan built a wall so massive most
0:07people on Earth have never heard of it.
0:11It is taller than a four-story building.
0:14It runs 400 km.
0:16It cost $12 billion.
0:19400 km, New York to Boston and back
0:22twice.
0:23Every inch of it built by hand.
0:27That was 2011. This is today.
0:31The wall exists because of what happened
0:33on the left.
0:36Wait, this wall is now so high you
0:38literally cannot see the ocean from your
0:40home.
0:42>> My husband ran toward the sea. I never
0:44saw him again.
0:46>> Every meter of this wall was paid for in
0:48grief.
0:50Now watch what they actually built.
0:52But engineers warned, if this wall
0:54fails, it could make the next tsunami
0:57far deadlier.
1:05March 11th, 2011.
1:08The ocean floor moved 50 m in 3 minutes.
1:11What came next was unstoppable.
1:14That rupture displaced 500 cubic
1:16kilometers of ocean.
1:18The wave crossed Japan in 30 minutes.
1:21Not a wave, a moving wall of black
1:24water,
1:2540 m tall.
1:27Nothing in its way survived.
1:2990% of Japan's seawalls failed in that
1:32single hour.
1:34Every engineer in Japan took notice.
1:35[music]
1:37The world's largest breakwater,
1:40$1.6 billion
1:42destroyed [music] in seconds.
1:44>> It did not break from the front.
1:46Water topped it, eroded [music] the back
1:49face,
1:50foundation vanished.
1:53>> That is the engineering problem.
1:55One mayor, one wall,
1:573,000 people alive.
2:00That village gave Japan its blueprint.
2:02Build it taller.
2:05Now, you might be thinking,
2:06"How do you design a wall to stop an
2:08entire ocean?"
2:10Here is the brutal truth.
2:12This wall was never designed to stop
2:14[music] the 2011 scale wave.
2:17Here's the crazy part.
2:18Most of this wall is underground.
2:21Only 14 m shows.
2:23Engineers modeled this wall 200 times in
2:26a computer before placing one single
2:28stone on the coast.
2:30>> Wall height changes every kilometer.
2:33Taller on exposed headlands, lower in
2:36sheltered bays, designed from wave data.
2:40>> 440 separate teams.
2:43If even one goes bankrupt mid-build, a
2:45gap opens in the wall.
2:48Zero tolerance.
2:50Before one stone is placed, survey ships
2:52drill the seabed.
2:54Every section is different below the
2:56surface.
2:58>> Three foundation types: soft clay, dense
3:01sand, hard rock.
3:03Each requires completely different
3:05engineering underneath.
3:06>> First task, demolish the walls that
3:09failed.
3:10Study every failure mode.
3:12Then build the new one bigger.
3:15400 km,
3:16measured meter by meter before a single
3:18machine starts digging.
3:21This step takes months.
3:24They cleared an entire coastal pine
3:26forest.
3:27Erosion matting follows the bulldozer
3:29within minutes,
3:30always.
3:33The tide gave them 4 hours daily on the
3:35seabed.
3:37Every single minute was counted.
3:39The clay zones cannot even support a
3:41bulldozer.
3:42The ground is dangerously soft down
3:44there.
3:45Steel road plates spread the load.
3:48The machine floats above the mud.
3:50Simple, effective,
3:52crisis over.
3:55They are building the foundation 25 m
3:57below sea level
3:59in the active surf zone.
4:01Right now.
4:03Divers guide 5-ton boulders into
4:05position underwater
4:06in the same ocean that just destroyed
4:08the coast.
4:10>> Engineers check the underwater progress
4:12by sonar.
4:14They cannot see it.
4:17They must trust the data completely.
4:20>> Between boulders and fill sits a filter
4:22layer.
4:23Miss it, the wall slowly bleeds away.
4:27After weeks underwater, the rubble mound
4:30breaks the sea surface.
4:32Watch what comes next.
4:37That geotextile membrane [music] stops
4:39fine soil particles migrating into the
4:41rubble. It works silently forever.
4:45An uncompacted mound settles [music]
4:47unevenly. A settling foundation tilts
4:50the wall.
4:51Every roller pass is preventing failure.
4:55>> A 1 to 1 and 5 slope angle exactly.
4:58Steeper and boulders slide. Flatter and
5:01waves will not break on it.
5:03>> A platform is rising inside the ocean
5:06from nothing.
5:07Now the real wall construction begins
5:09above.
5:10Sheet piles driven 10 m into the ocean
5:13floor just to protect the wall toe.
5:16Z profile interlocks. That connection
5:19transfers shear forces between every
5:22pile in the wall.
5:23Critical detail.
5:25That steel wall fights the retreating
5:27wave, not the arriving one.
5:30Backwash scour is what destroys
5:32foundations.
5:34One buried boulder deflects a 12-m pile
5:36sideways.
5:38The entire alignment is now destroyed.
5:41Pre-drill the boulder first. Crush it.
5:44Then the pile drives straight through
5:46the cleared hole.
5:47Clean.
5:49>> The wave going back out is more
5:51dangerous than arriving. Backwash vacuum
5:54pulls the foundation sand out.
5:58>> 30 dump trucks running 16-hour shifts
6:00non-stop. One breakdown stalls the whole
6:03compaction cycle.
6:05300 mm lifts, no more, no less.
6:09Too thick and the compactor never
6:11reaches the bottom of it.
6:12Inside every seawall body, geotextile
6:15reinforcement layers.
6:17Like rebar in concrete, but for
6:19compacted fill.
6:2298% proctor density or the inspector
6:25shuts the job down.
6:27Every single layer tested here.
6:29>> Press your foot on 98% proctor fill.
6:33Nothing moves. At 85%
6:37sinks.
6:38>> 300 mm per day. 18 months until the
6:42first tsunami season with the wall
6:44standing.
6:45Counting.
6:49That clay core is the wall's internal
6:51waterproofing.
6:52Well compacted clay stops water
6:54permeating through [music] it.
6:56One night of heavy rain,
6:58600 mm of slope slumped.
7:01The entire section is rebuilt from
7:02scratch.
7:04A drainage pipe [music] network inside
7:06the embankment.
7:07Cover the slope with geotextile before
7:09every rain.
7:10Always.
7:12The wall hits 10 m. Thousands of
7:14concrete panels are coming.
7:16This is the critical part.
7:21>> This wall has sensors embedded inside
7:23it. Engineers watch it breathe and
7:25settle.
7:26Every day, forever.
7:28>> The face must be perfectly flat before
7:30any panel goes on.
7:32One bump creates a stress concentration.
7:36>> Three materials, three jobs.
7:39Grip the seabed, seal against water,
7:42carry the structural load. All one wall.
7:46>> If one of these 7-ton panels cracks in
7:48the mold, it ruins the entire week's
7:51schedule.
7:52Every hairpin bar connects the panel to
7:54the crown wall.
7:56One missing bar breaks everything.
7:59Self-compacting concrete flows around
8:01every bar.
8:03Perfect face. No honeycombing.
8:06That surface must resist a tsunami.
8:09Wrong slump and the panel face
8:11honeycombs.
8:13One bad batch fails the whole production
8:15run today.
8:17Listen to that tap.
8:19Solid ring means good concrete. A hollow
8:22sound means this panel [music] gets
8:24crushed.
8:25Zero tolerance for defects on tsunami
8:27walls.
8:28That panel is worth $800.
8:31It still gets crushed.
8:337-ton panels on narrow Japanese coastal
8:36roads. Flagman at every junction.
8:39400 km to cover.
8:42>> That bed is level to 5 mm.
8:45A hump cracks the corner of a 7-ton
8:47concrete panel.
8:49>> That face takes a tsunami at 30 km/h.
8:53It must hold for 100 years.
8:56400 mm lap sounds boring.
8:59Until you picture a tsunami ripping each
9:01panel off the wall.
9:03That rubber water stop swells when wet.
9:06The bigger the wave, the tighter every
9:08joint seals itself.
9:13Straight panels on a curved coast. 20 mm
9:16gaps opening. Water forces through and
9:19undermines everything below.
9:2137 unique panel shapes. CNC machined
9:25molds. Every gap closes to [music] zero.
9:28One curved bay perfectly sealed.
9:31One week seals 400 m.
9:33>> [music]
9:34>> But the 2022 deadline is counting down.
9:37440 teams racing simultaneously.
9:41The crown wall nose throws overtopping
9:43water back over the seaward side. One
9:46detail protects thousands.
9:48The crown wall grabs every panel below
9:50through hairpin bars. One integrated
9:53structure, not individual stacked
9:55pieces.
9:56Pump boom maxed at 15 m. If it fails
9:59mid-pour, a cold joint forms. Wall
10:02compromised.
10:04>> 10° from vertical. That single angle
10:07throws overtopping water outward instead
10:09of crashing inward. Simple genius.
10:13>> The only decoration on 400 km of wall a
10:16stamped wave pattern on the coping.
10:20They measure the crown wall height for 5
10:22years after completion. Monitoring never
10:25stops.
10:26>> Six materials.
10:28Six engineering functions.
10:31From outside it just looks gray.
10:34It is not.
10:35>> The back matters as much as the front.
10:37Back face failure is what killed the old
10:39ones.
10:40If water tops the wall, it must go
10:42somewhere safe.
10:43>> [music]
10:44>> The landward drain is that escape route.
10:4732-ton concrete blocks. Each one must
10:50interlock or the entire armor layer
10:53shifts in the first storm.
10:55One leg always points upward catching
10:58the next tetrapod above.
11:00That interlock absorbs wave energy on
11:02impact.
11:03They are not placed precisely. They are
11:05dropped. They find their own stable
11:08position. Chaos creating order.
11:11The gaps between tetrapods are not a
11:13weakness. They are the mechanism. Water
11:16flows through. Energy dissipates.
11:19>> 1 L of water completely absorbed.
11:23Now imagine that multiplied by 50
11:25million tons of tsunami.
11:27>> There is a formula for this. Van der
11:29Meer equation. Input wave energy. Output
11:32minimum armor weight.
11:3440 tetrapods per day, 400 km of
11:38coastline to armor.
11:40This yard never stops, day or night.
11:44Below the waterline tetrapods pile up
11:46unseen.
11:47Sonar shows what no diver can reach at
11:49that depth.
11:51Three lines before the wall, rubble
11:53mound, sheet pile toe, tetrapod armor.
11:56The tsunami exhausts itself first.
12:00Every wall section is tested in a wave
12:02tank right now, and some results are
12:04unexpected.
12:08443 gaps in the wall, each one a death
12:11trap if a single floodgate fails to
12:13close.
12:15Floodgate concrete is twice as thick as
12:17normal.
12:18This is exactly where tsunami forces
12:20concentrate hardest.
12:2270 seconds from alarm to sealed, the
12:25only window before the wave hits the
12:27coast.
12:28>> [music]
12:28>> A seismic sensor triggers automatic
12:30closure.
12:31No human needed.
12:33Earthquake starts, gate begins closing
12:35immediately.
12:35>> 15 mm clearance, 50 tons of steel, 40
12:40km/h coastal wind during installation.
12:441.5 times design pressure. If one of 14
12:47seals leaks, the gate completely fails.
12:5140 L per minute through a 2 mm gap.
12:55Under real tsunami pressure, that gap
12:57becomes 20 mm.
12:592 mm ground off.
13:01Retest. Zero leaks.
13:043 hours of machining saves a whole town.
13:08A driver caught in this gap when the
13:10alarm triggers, the gate closes in 70
13:12seconds.
13:14A 22-m steel curtain must seal the river
13:17mouth before the tsunami wave arrives at
13:19the coast. Stored open at the top.
13:22Gravity closes it.
13:24Power fails, the gate still comes down.
13:29443 gates, one command room, 4 minutes
13:3320 seconds.
13:35Japan drills this every March 11th.
13:38>> 400 km of wall,
13:40one screen,
13:41every gate, every [music] sensor, every
13:44alarm.
13:45The wall thinks for itself.
13:47>> On cliff sections, there is no beach.
13:49The wall goes directly into the rock
13:51face.
13:52Rock bolts, 2 m into basalt.
13:5550 km/h coastal winds during drilling,
13:58wall bolted to mountain.
14:01Concrete sprayed at 100 km/h bonds to
14:04rock better than poured.
14:06The cliff becomes the wall.
14:08The tsunami hits concrete bonded to
14:10shotcrete bonded to basalt.
14:13Three materials, one integrated face.
14:16Nothing moves.
14:18A submerged breakwater [music] trips the
14:20wave 200 m offshore before it even
14:22reaches the main coast wall.
14:25A 60,000 ton box floating in 3 m swells
14:29being sunk to 63 m.
14:32Watch what happens.
14:35The tug loses steerage in 30-knot winds.
14:38That 60,000 ton box drifts 8 m off its
14:41mark.
14:43The rebuilt Kamaishi breakwater is
14:45stronger than the world record it
14:46replaced.
14:48Always build back stronger.
14:53If this panel fails the strength test,
14:55the entire week's batch [music] goes to
14:57the crusher.
14:582 mm of carbonation,
15:01the reinforcement inside will not see
15:03sea air for at least 100 years.
15:05The independent inspector can fail any
15:07section and order demolition.
15:10440 contractors under that pressure
15:13constantly.
15:14Twice the design load on the gate frame.
15:17Engineers watch strain gauges. It holds
15:20well.
15:2114 mm of differential settlement across
15:24400 km in 2 years on coastal sandy
15:27ground.
15:28Exceptional.
15:31A 7.4 earthquake strikes.
15:34>> [music]
15:34>> The sensors fire.
15:36All 443 gates are now closing
15:38simultaneously.
15:42>> Zero cracks. Zero shifted tetrapods
15:45after a real [music] 7.4 earthquake.
15:48That result is extraordinary engineering
15:50performance. [music]
15:51>> Watch this.
15:53The pump is running on the last section.
15:55400 km is almost sealed. Almost alive.
16:02A helicopter is flying the full 400 km
16:05right now.
16:06What it photographs will change
16:08engineering forever.
16:10These staircases are not scenic
16:12overlooks.
16:13They are emergency evacuation routes
16:15designed [music] from crowd flow
16:16science.
16:18People cycle along the top now. Walk
16:20dogs. Run every morning.
16:23The wall became a daily [music]
16:24promenade.

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