London recently built some new underground tunnels. (Well, recent in terms of the history of London.) They did this by drilling under the city – avoiding all the existing tunnels, water mains, building foundations, etc. – using 8 tunnel boring machines (TBM) from the German firm Herrenknecht AG. (Pronouced “Heron-connect”.)
These machines cut through the rock and clay, removed the material, and build a reinforced-concrete tunnel shell as they go.
The most interesting video on the subject is from Dirty Great Machines (that video is after the break), but since it is 45 minutes or so, I know that most people won’t watch it.
If you are only tied into the hype spread by American media, you might think that Elon Musk developed TBMs, but Herrenknecht has machines drilling tunnels all over the world. Train tunnels, sewer tunnels, all kinds of tunnels. It’s just the infrastructure that makes modern life possible.
Here is a 2 minute video that is sadly very dry, but does manage to be fairly instructive in how these things work.
After the break you will find an episode of the short-lived TV show, Dirty Great Machines, on how TBMs are designed and built, tunnel boring operations in London, and Mexico City. There is also a bit of information on the Roadheader, a smaller machine used in tunneling that can make sharper turns.