Quote Originally Posted by pisshead
http://science.howstuffworks.com/building-implosion.htm
Yes, that's the normal process. I am aware of what's involved. In an emergency situation, however, it can be accomplished much more quickly. It only takes a few hundred pounds of HE - usually PETN or a similar material - to bring down a building of that size. Shaped charges cut steel support members, while larger charges are loaded into concrete load-bearing structures. Properly timed, these charges pancake the building down on itself.