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Tunnel Boring Machine Under River
Wet, soppy soil seeped through the seals and stopped this rock-eating machine in its tracks.

Tunnel boring machine _+_ Under water __ Caution
Learn more       Tunnel Score: 10

Tunnel boring machines (TBMs) prefer to chew rocks, not mud. Besides, they can't support the wet ground, so the tunnel walls are collapsing! TBMs work much better in rock tunnels. Try this technique in a rock tunnel to find out why!


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