You may have a few conceptul hurdles to overcome.
1] What would happen to the survivors when they are hit with a shock wave powerful enough to shatter concrete?
ok i'll admit we have some hurdles.
2] What would happen to the survivors when the concrete is shattered to rubble over their heads?
my thought, I was one of the people that was in the oakland bridge collapse trying to free people from a very unstable structure. but i noticed then we had to shore up the bridge on top of us, but we some of the tools were to big to get into the small areas. If i could have shored up the area around the victim and had a smaller unit that would blast the concrete off it would seem to be easier and faster ( in a perfect world )
3] What would happen to the structure - already highly unstable and liable to collapse at any moment - if you start reducing parts of it to rubble?
we would still have to shore it up around the traped people, maybe the rubble could be vacumed out with the large 8" hose.
just a thought
forgive the spelling errors
Joe c