A caisson in May ( 50+ photos )

[harryc]

This sequence is the last part of installing a caisson on the Chicago Spire project.

I arrived as they were lifting up this sleeve.
1

2

3

Then lowering it into the already drilled ( and belled ? ) shaft.
4

5

6

Here the tape measure has been tied to the top of the sleeve with plastic tape ( can be pulled off with a strong tug ).
7

Riding the sleeve down
8

9

Carefully measuring
10

The red reel is the saftey line.
11

12

Guy in white helmet is checking the numbers while the one in back prepares a bucket full of tools and shims (?). He wears the notbook in his tool belt and consulted it seemingly at every step.
13

A pretty pink plumb line
14

Another bucket of tools
15

16

Preparing a foot loop
17

UP and out
18

19

Emotional welcome - or just unhooking him ?
20

Hooking up the first (bottom) segment
21

Up and in
22

23

24

25

Down and held in place with the 2 poles
26

27

28

Rigging the next segment
29

Up & Over
30

31

Fit #2 over #1
32

33

Squeeze down
34

Tie off
35

36

37

Pull out the pipes
38

39

Ease it down
40

Hold it again with the pipes
41

Reconfigure the hooks, and tie on the measuring tape again. Replacing the s rewed together - won't come apart - lugs with simple hooks.
42

43

44

45

46

Lowering the completed cage ( into the sleeve ).
47

At this point the tape read 21'
48

All the way down
49

50

Tie off the cage ( held up by the chains - one set visable on the left )
51

Unhooking
52

Cable up
53

Securely tied off
54

Filler Up
55

On the 2nd of three truckloads, filler gravel has been delivered ( this will be used to bury the caisson ).
56

The descriptions are from what I have deduced.
Corrections, Clarifications, and additions would be very welcome.

[Kelvin]

It all seems pretty concise.

[Coldrsx]

great report, thanks. I was going to say...that 1st rebar they lowered was pretty wimpy, but then i scrolled down.

[Jibba]

This was a great documentation of the process, harryc. I have been trying to piece the parts of the process together from the random shots interspersed into your Spire posts, but now that they are all isolated and ordered here it is much easier to see what is going on. Thanks!

[alsajano]

A very good information.

[Lecom]

Fascinating. Thanks a lot.

[Nowhereman1280]

Harry, your picture narratives certainly add a lot to this forum, I always enjoy reading them and seeing a step by step of how things are done on these sites!

Thanks!

[mdiederi]

Great photo documentary, as usual harryc.

That must be very claustrophobic having to go down inside of that thing.

[harryc]

Originally Posted by mdiederi

Great photo documentary, as usual harryc.

That must be very claustrophobic having to go down inside of that thing.

Yes in photo 20 there was definitely some relief and emotion involved when he got back up.

[Vexxed8282]

Great pictures and analysis. I have a few clarification questions. Is the sleeve the exact diameter of the drilled hole? When I look at the caisson top it appears as the diameter is quite a few feet on each side. Is this extra width only for the first few feet? I wonder because it looks like the caisson could shift from side to side. If the diameter is much bigger then the sleeve, do they then fill the sides in with the gravel? I hope this question makes sense. Thanks

[Colin Giersberg]

While I am not sure of this, I believe that the outermost section of caisson will be pulled out as the concrete is poured in. The photos make it look like that is not the case, however. On a bridge project that I was on, the outer section was to prevent the surrounding material from collapsing. The man that was pulled out probably went down to inspect the bottom of the caisson to make sure that there were no voids in the floor. If there were, they would have to drill down further to get to solid rock. The outer sleeve has notches cut into opposing sides (which you can see) for a drive bar to fit into. This would be at the bottom end of the "Kelly" bar, and when engaged, the entire tube would rotate. It should have teeth on the bottom end to cut into the rock, which is then excavated by using an auger that also has teeth on the cutting edge. One it is cleaned out, the man would have to go back down and re-inspect the floor.
Since they have lowered a rebar cage into the hole, the floor should be okay. As the concrete is poured, the outer section would be pulled out, the concrete would then fill the hole up and prevent any collapse from the surrounding material. The rebar cage does look rather small in diameter to me, and I don't know what the steel tube placed in the hole is for, but it looks like it forms the permanent sides of the caisson, but it is smaller than the outer casing, so I am confused about that.

Hope this may clear up the operation some.
Regards, Colin

[harryc]

Yes the outer portion ( caisson top ? ) was pulled out later. The inner liner ( caisson sleve ) is still in the ground, and will be cut off as needed when the site is excavated.