Please move this forum to the under-construction sub-forum:
http://forum.skyscraperpage.com/showthread.php?t=200023&page=3
Post #47, second photo down, indicates installation of caissons. If one looks to the left of the drill rig, a completed caisson is visibile, Another completed caisson is visible between the drill mechanism and the rig, just above the tracks.
Threaded Mode