http://www.seattlemag.com/gallery/closer-look-bertha?page=3
Here’s an article with some photos. It says it can “swallow” boulders 3 ft. in diameter. I’m guessing that what look like openings in the cutting face ARE openings so that the material can make its way from from the face, through the cutting head, and then onto conveyors out the back of the tunnel to get hauled away.
It seems that they must be taking their time in exploring what the object is on the off chance that it is some sort of man made object such as a pipe (doubtful at 80-feet deep), building footing (also doubtful), or whatever.
I’m still not up to speed on the whole pressurized thing. If it is just the face of the bit that is pressurized - then how could they have all of the holes in the bit to allow the waste material through? So maybe the pressure has something to do with why they can’t send some miners down with jackleg drills, etc. to explore.
Anyway - it will be interesting to see what it is, and more importantly, how they solve the problem.
https://twitter.com/BerthaDigsSR99
A link to a photo of the “middle body” of the tunnel boring machine. Looks a lot more complicated than I can imagine. Looks like it would be quite the effort to get men and equipment through this and up to the front of the machine.