The Iranians are using a sophisticated form of concrete called UHPC(Ultra High-Performance Concrete), Also called "Smart Concrete."
When the Air Force first received the MOP in 2011, it was unknown if these bombs would be able to penetrate several feet of UHPC.
So the bombs had to back sent back and upgraded.
No matter how deep they may be they have to have entrances/exits - MOP those up. Everything else is buried for years. Then bomb it again.
Yoo Hoo - CIA, FBI, NSA, Israel, Echelon, Iran, Terrorist, Nuclear, Bomb, secret, classified, eyes only, confidential, sex, hooters, gay, soviet, china, syria, radiation, Mossad, etc. hint hint. Goodbye cruel world. I wonder if this thing is loaded? Oh wait, lesbian, dead, murdered, blackmailed, buried, Obama, useless, stinking, POS ... ;-)