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This machine is longer than a football field, and it eats through solid rock without a single drill bit.

So if it isn't drilling, how does a tunnel boring machine actually break through stone that hard?

The front is a rotating steel wheel studded with hardened discs. Hydraulic cylinders behind the machine push it against the rock, and as the wheel turns, each disc rolls across the stone like a pizza cutter under thousands of tons of pressure. It does not grind the rock away. It presses so hard that the stone fractures, and chips flake off in slices. A conveyor belt behind the wheel carries those chips out the back. Meanwhile the machine builds its own wall as it goes, so digging and lining happen at once.

Here's the strange part: it never really cuts. The discs simply squeeze the rock until it cracks itself apart. The machine wins not by being sharp, but by pressing harder than stone can survive.

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