Fuel air explosives are probably the best bang per pound of crap that has to be carried and emplaced.
But how can you disperse it optimally down a tunnel 1/4 to 1 mile long?
A motorized cart (or the new guy, after some clearing procedure) emplaces bucket-sized charges connected by a fiber optic command link?
A series of line charge sprayers?
A big fan?
A slow spray until calculations or sensors indicate she’s ready to blow?
Yeah, that’s the problem. I suppose some sort of high pressure sprayer and fans could get it quite a ways in and then when she blows the shock wave would affect people a lot farther down than just the area of the explosion. Especially in such a confined space.
not necessary if it is heavier than air and fuel vapors are, or could be bonded with something else so they would be... ) so no need for complicated process to disperse the gas. All that is needed is the fuel vapors and a spark.