Pipes, in his lifelong streak of shitty luck, just so happened to walk right over one of those tripwires while investigating the noise of the elevator. Luckily, he realises that the snapping noise after activating one of them wasn't a normal noise (at least, not one he'd heard after weeks of exploring) and manages to just about avoid being flattened by the bigger rocks. Just about - he gets covered in dust and several of the smaller rocks do hit him in the back and shoulder, sending him sprawling out on his stomach.

He lays there for a while, in a daze and wondering how that happened before eventually stating flatly, "Ow."