Are those for driving the thing forward or for turning the cutting head?
Looks like turning to me. I think forward motion is inchworm-like.
Of course, I failed to grasp what they're doing down in the hole.
I'm surprised that they let you get that close. I mean, you might fall in! Probably better to wait until it's in operation, though: death by boring machine would make you famous forever.
Hey, I was outside the fence.
But this time, one of the guys did yell at me eventually. Jerk.
If they didn't want people to get that close, they should have put the fence farther away.
"You don't see us coming to your work and yelling at you". "Yes, yes you do. I sell beer."
Good Lord! If I was finely separated but compact presedimentary rock and gravel, I would be terrified!
I am vaguely reminded of the late 70's Lego motor (this one: http://www.brickset.com/detail/?Set=870-1) with a small gear on it.
That's pretty accurate, but I'm not sure the video Marshall linked to above shows that they protrude diagonally relative to the face of the bore hull.
We have a nice bored tunnel as part of our most recent rapid transit line. Standing in Olympic Village station and looking South, the tunnel is rectangular in cross section (it was cut-n'-cover). Looking North, the tunnel is circular (it was bored with a TBM). TBMs are the business.