River East top-down vs. Chicago Spire...really bothering me

[Vexxed8282]

I was in the cavernous River East parking garage the other day...seeing Batman...and I noticed how good the behemoth caissons look. Then it dawned on me...If the concrete is exposed, they couldn't have used steel sleeves like the Spire, so they must have used "cardboard" tubes that they could peel off to expose the spiraled concrete, except for the caissons along the perimeter. The perimeter caissons, embedded in the slurry walls, are in steel sleeves which look to be quite rusty.

I found this link on Case's website, http://www.casefoundation.com/projects/rivereast.aspx ,which explains the River East process quite well. Anyway, my questions is this. In this application, did they use the cardboard tubes instead of the steel sleeves used in the Chicago Spire? If so, what are the advantages/dis-advantages, reasons, etc.? Or is there something I am missing, or didn't notice. Thanks. If I am right, what do you think will be the finish treatment will be on the Spires steel sleeved caissons in the garage? Thanks

[Kelvin]

There are two ways to do a caisson - leave the sleeve in or take it out. Usually the sleeve is used to keep a hole from sloughing in after it has been drilled but before it gets concreted. The sleeve is then pulled up as the concrete goes in. There is practically no difference whether it remains or gets removed (structurally) as the concrete is expected to most of the work and rebar will be added if needed.

IN other instances, we use a thicker steel pipe section when we design the pile to have load applied through the wall and then just infill with concrete to keep the section from getting filled with other debris (or not). Usually this type of pile are for smaller sections - say 20" or less. The pile can be driven open-ended or with a point (an then filled or not filled).

For most large-diameter pile/caisson sections, the pile sleeve or pipe section is made from spiral weld sections similar to how a cardboard section is made, but much sturdier. A cardboard section would almost certainly fail (blow) in this application. There are a couple of photos in the link that show a spiral-weld "tube" getting ready to go into the hole. There are some aspects I can't quite explain (like how they stripped the caisson leaving only clean surface and the regular spiral lines). The photos (#4 & #13) show corregated steel panels in spiral formation (as opposed to spiral weld pipe). So why isn't there a corregated surface in the concrete (unless there was an inner case and an outer case...). How did they get it off without damaging the surface? Perhaps it was stripped off piece by piece or perhaps they were able to twist it off like a bottle top!