In the early decades of the 19th century, London was facing a major problem. The city had become the world's busiest port, but in order to transport goods from the docks to the heavily-populated ...

Here's how the tunnel boring machine, or TBM, works: As the 200-ton TBM moves forward, a round cutter head studded with titanium teeth grinds into the tunnel face and splits large chunks off the rock.