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  • 10.20.09

Infographic of the Day: How Do You Dig a Subway Tunnel, Anyway?

You’re probably surrounded by massive infrastructure projects, with precisely zero idea about how any of them came to pass. What kind of man are you, huh?

Well, this should help: The Washington Post has produced a ginormous infographic detailing the tricky process of digging the 2,400-foot subway tunnel that’s slated to bring subway service to Tyson’s Corner in Northern Virginia.

Subway Construction

Normally, the easiest way to dig a tunnel–the way old-time subway engineers relied on–was to simply dig a huge trough, build the tunnel, and cover it back up with dirt. That’s being used here, at the beginning and end of the tunnel. But there’s also a cutting-edge “Austrian Technique” being used to speed things up.

It’s all about a highly choreographed sequence of moves: First the ceiling is jammed with steel rods, which reinforce the top of the soon-to-be tunnel. Then the top half is excavated; during the process, the exposed earth is lined with girders and sprayed down with “shot-crete,” which stabilizes everything. Then the bottom half is excavated and reinforced with girders and shot-crete. And here’s what’s really stunning: The machines are precise enough that they align the sections within one-millimeter tolerances. Lasers monitor the walls, to make sure everything’s going right. The workers and machines are able to dig about five feet a day.

Total cost: $85 million. Or, about $35,417 per foot of tunnel.

For the full-sized version, and more information, check out The Washington Post. And after that, retreat to your man cave and roar mightily! Rar!

Subway ConstructionCK