solarz
Brigadier
It's how Zombies are able to get through fortifications. Instead of breaking through them like a bullet which uses high velocities to penetrate, a Zombie horde uses almost pure mass to break down a barrier.
For example, if you get one American Football team and have them tackle a solid concrete wall, I bet $50 USD they will fail. However, get 1,000 Zombies, have the first 10 push the wall and have the next 990 push the first 10, and I will wager $50 that they will succeed.
Nah, remember that zombies are still just meat. 990 zombies pushing 10 zombies against a solid concrete wall won't result in a crumbled wall, but rather 10 mushed up zombies.
It's like trying to punch through a wooden board with a cardboard tube: doesn't matter how strong the force behind it is, the tube will be crushed before the board is even dented.