On a machine like this, there has got to be a way to take a *core* sample from what's in front of the head, much like what is used in oilfield work (Explosive charge core gun or a mechanical coring tool used in hard rock country).
Heck, even a small shape charge used in perforating guns on a well could be used to blast out a sample.
Can't see them building such a sophisticated machine without that capability.
From what I’ve been reading, they have to back the machine up a few feet to allow a crew to examine the cutting face. Apparently, it’s rough work. They have to don special gear, and work in a very confined space. I suppose they carry the tools to take samples and so-forth.