That’s the reason why I asked the question.
Take a look at this http://en.wikipedia.org/wiki/Bunker_buster for background.
Kinetic high density penetrators have limits - even if ‘assisted’ by being dropped by aircraft.
The same device, aided by a rocket motor will go deeper.
The same type of device, preceded by an explosive jet of gas will be able to penetrate deeper and do more damage.
Until the USAF is able to procure a working DUODEC (duodecaplylatomate) or are successful in producing an allotropic iron bomb, these represent state of the art.
An alternate would be an aircraft mounted DeLameter blaster, but focus problems pose a real issue....
Have fun, it's Friday!