From a little exchange on sci.space.policy (with minor editing)...

Ed Wright suggests:

If one were to set up a large rocket engine at the mouth of the cave complex--or several mouths --and run them, what would the resulting decibel level be inside the caves? To maximize the effect, I suppose you could direct the exhaust into the cave.

I know that sound tends to reflect (echo) inside of caves. How deeply would it travel, and what would the effect be? Would decibel levels be above the threshold of pain? Could they cause internal damage to cave dwellers or structural damage to the caves themselves?

Or would it simply be annoying, like the existing psyops tactic of playing loud rock music throughout the night?

To which Doug Jones responds:

A rocket isn't necessary- just use a jet engine on afterburner, this would be logistically simpler and much more readily available. If the exhaust is ducted into the cave (and there are other uncovered exits), the breathable air inside would be very quickly displaced. This would be a bit like cave clearance with flame throwers as used in WWII, but much more effective for large tunnel complexes. I dunno if the carbon-monoxide-laden gases could be construed as a Geneva Convention violation, though.

More conventionally, some combination of laser-guided bombs to seal the entrances together with fuel-air explosives forced down ventilation shafts would be more than sufficient. Heck, if water is available nearby, take a page from the prison riot resolution, bring in a bunch of fire pumpers, and flood them out. Undramatic but effective, and perhaps a better psyops tactic by not martyring a lot of enemy troops.

And they said Usenet waren't good for nuthin'...

In Viet Nam, it was discovered that the NVA and VC had designed their tunnels with at least two right-angles in the entrances. Two or more right angles work pretty well as a kind of cork, stopping the force of explosions set off at or in the mouth of the tunnel.

It seems, given the TV animations, that the caves in question have right angles, either naturally or as a matter of construction.

The solution in Viet Nam was to pump gasoline vapors into the tunnels. The low velocity of the air flow laden with gasoline vapors permitted the tunnels to be filled with the vapor.

The thing was then lit off.

Since the explosive (gasoline vapor) was mixed all through the tunnel with the oxidizer, the explosion took place all through the tunnels.

Charlie dealt with this by taking civilians into the tunnels with him, making civilian casualties inevitable.

The US countered by switching from gasoline to tear gas. This had two effects. It worked, and it energized the anti-war folks who thought of it as "chemical warfare" and thus forbidden.

They liked it better with civilian casualties they could blame on the US.

If the US gets to the caves in Afghanistan soon enough, there may not be enough time for the inhabitants to round up any locals as shields.