>>508709789 (OP)>>508709870I been saying this for like weeks now. Bunker Busters in the 90's used concrete that was not meant to be impact resistant. There were early signs of concrete improvement in the 2003 invasion of Iraq and bunker busters from the 90's were not working as good anymore.
Iran is a leader in researching ways to strengthen concrete to resist impact forces. Such as a bomb hitting it. What they do is add steel microfiber hairs in the concrete, which help adsorb the impact force. Concrete is good in compression, not fast hard impact.
Concrete now is 10x stronger compared to older concrete from a decade or two ago.
So a bunker buster that used to be able to penetrate 10ft of concrete can only go though 1ft of this new treated concrete.