You can use the collapse scenary for it to collapse when you walk over it, that needs a special animation which I'm not sure about it so I'll let someone else exaplin.
Distructive scenary can be destroyed by weapons, set the animation to have three tiles: BEFORE then AFTER then BREAKING, so basiclly: a wall, then a broken wall (or jsut air) and last some rubble which'll fall when destroyed.
Buttstomp scenary can be destroyed by Jazz's upper-cut, spaz's kick and buttstomping. It's animations work on the same principle of destruct scenary.

Welcome to JJ2 and this belong in the JCS forum n.n

PS.maybe also the collapse scenary's animations work like that.