A bomb penetrating 18m of reinforced concrete doesn't excavate 18m of concrete. It would weaken it by some percentage through fractures and overpressure but you'll need to pen it again with the second bomb.
I know a bunch of armchair generals on here are speculating that this was ineffective, but time will tell.
Why do you believe that to be true?
Military: We can penetrate up to 200 feet with this new bunker buster bomb that we spent a billion dollars on…specifically for this site and some sites in North Korea.
Enemy: Build the bunker at 300 feet, I hear their best bunker buster is only effective to 200 feet.
Military: Damn, foiled again!