They can be triggered more than once, because they are not exploding but just releasing gas when stepped on. However, they will be discovered when triggered, so you won't randomly trigger them again and again. They also have a high chance of breaking whenever triggered and can be disarmed by picking them up or kicking them from adjacent square.
What do you mean by "they will be discovered"? I didn't see anything visible on the spot where the trap was.
I think it was in GC - maybe they are visible in TX but with the coloration of the floor in GC they're difficult to see? That was one thing I noticed with my skeleton puppies, they're easy to see in the catacombs but nearly invisible in TX.