I can't remember if the floor in here can take portals,but if not, all you have to do is make a portal on a side wall or behind the turret after the door opens, then walk through a portal to get behind or beside theturret, pick it up and tip it over.
Now, don't panic.Remember, turrets are easily disabled by making them tip over. The doors each have a turret standing inside. When you walk across them, they willmove out of the way such that you can't walk across to the ledge beyond.In this pit, three doors will open on a time delay. Otherwise, go the other way and you will reachan area where the floor is blocked by several horizontal pistons. Crawl into the vent if you want, and look around.
