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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