[City Wide]

Originally Posted by LouisVanDerWright

Notice how you never just see a giant cassion sleeve like the ones delivered the other day just sticking 3/4 of the way out of the ground? You will never see that because the equipment couldn't possibly work with a 100' long sleeve all at once. What they do is drill in a 22' wide by 25' long one, then lower a 50' long by 21' 3" sleeve into the existing hole so only 25' is sticking out. Then they telescope that one all the way into the hole and then they bring out a 75' long by 20' 6" one and drill that all the way in. THEN comes the big boy which is say 20' even wide and 100' long and drill that all the way down. Once they've "telescoped" to the right depth they bust out the rock grinders, make their socket, and then lower a all the way into the hole with the rebar cage in the middle a pour away.

I actually wondered about that a long time myself, how do they keep reusing the sleeves? How do they get them out? Why do you never see a super long one just like halfway drilled into the ground? Then I watched them working at this site the other day and saw them dropping a medium sized one into a larger hole and was like "gotcha". I suggest going down to watch this site, it's immensely impressive. Watching a rig like this torque the big sleeves that have hundreds of square feet of surface area against thick Chicago mud is quite a sight.

Lets see if I've got this right----drive a large diameter sleeve into the ground as deep as possible. (I assume that the friction between the sleeve and the ground limits the depth of this drive, bigger diameter=more surface area rubbing against the sleeve=shorter depth, small diameter = less friction = greater depth) then drill and remove the debris from the center of the first sleeve. Repeat these steps with a slightly narrower sleeve but of course it will drive deeper since the top section is not in contact with any dirt.
Then at some point in time a "permanent galvanized corrugated sleeve" is put in the full depth hole, a rebar cage is fit into the permanent sleeve which gets filled up with concrete.
Question, I've only ever seen this type of caisson construction done with 2 sleeves. Is this because 2 sleeves gets one down 100' or so, but if needed this principal of what you call telescoping could be done with as many sleeves as needed.
I have never seen a "permanent galvanized corrugated sleeve" why bother with the cost of galvanizing and corrugating? This last sleeve is just a form for the concrete, rust won't be a problem.
I assume that the reason for adding this permanent sleeve/concrete form/ and not just leaving the drilling sleeves in place must be cost. The drilling sleeves look major league compared to the permanent sleeve
After the permanent sleeve is filled, or maybe as it is being filled, are the drilling sleeves removed and the space they took up backfilled with dirt or grout?