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Subway tunnels aren't dug by explosives or hand tools — they're carved by tunnel boring machines, steel giants dozens of meters long that cut rock, remove debris, and install concrete tunnel lining simultaneously as they advance. The rotating cutter head grinds through rock while hydraulic jacks push the entire machine forward, and mechanical arms inside assemble concrete segments into complete rings that permanently reinforce each freshly dug section. Workers operate entirely inside the steel shell — protected from collapse at all times. Once dominated by foreign manufacturers costing hundreds of millions per unit, TBMs are now fully produced in China and exported worldwide, boring tunnels from Asian cities to European infrastructure and undersea crossings. That perfectly smooth tunnel above your head on the subway was carved by one of these machines in complete darkness.
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Transcript
00:00Do you know how subway tunnels are actually dug?
00:01No explosives, no manual digging.
00:03The real work is done by one massive underground machine, the tunnel boring machine.
00:07This giant is dozens of meters long with a diameter close to a small building.
00:10Moving underground it operates like a steel earthworm,
00:12with a massive cutter head at the front covered in hardened cutting tools.
00:15The machine starts, the cutter head rotates,
00:17rock layers get cut open, soil gets ground down.
00:20Simultaneously hydraulic jacks at the rear push with hundreds of tons of force,
00:23driving the entire steel beast forward inch by inch.
00:25But the TBM's real strength isn't just boring.
00:27It installs the tunnel while digging.
00:29Inside the machine mechanical arms lift concrete segments one by one,
00:32assembling six or seven pieces into a complete ring, locked and fixed.
00:35One full concrete lining formed instantly.
00:37The jacks push against this ring, the machine advances forward, digs another section,
00:41installs another ring, dig and reinforce simultaneously every meter of the way.
00:45That's the core logic.
00:46Underground the biggest threat isn't rock, it's collapse.
00:49In the past workers stood at the very front,
00:50and any ground shift could bring soil and rock crashing down instantly.
00:53The TBM encloses the entire operation inside a steel shell.
00:56Cutting at the front, protecting in the middle,
00:58reinforcing at the rear.
01:00Workers operate safely inside at all times.
01:02For a long time TBM's were almost entirely monopolized by foreign manufacturers,
01:05with single machines costing hundreds of millions.
01:08But that's completely changed now.
01:09China has achieved full domestic TBM production.
01:12Not only building them locally but exporting worldwide.
01:14From Asia to Europe, desert to seabed,
01:16more and more tunnels are being bored by Chinese machines.
01:18So next time you ride the subway through the city underground,
01:20that perfectly formed tunnel above your head was very likely carved out by one of these steel giants in total
01:24darkness.
01:25.
01:25.
01:25.
01:25.
01:26.
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