Tuesday, July 6, 2021

Skyscraper Foundations in a Swamp (Piles)

This was one of the first topics I had planned on writing about when I started this blog in 2014. I've been accumulating photos for drilling the piles for years, but never found the time to research it. I knew from a tour of Northwestern University's Tech Center in 1967 that a lot of research was done to figure out how to safely build in a swamp. They had a plexiglass 2' cube filled 2/3rds with sand. And they added water to the sand to emulate the soil conditions of Chicago. The tour guide picked up scale model houses and other buildings and set them on the sand. They did not sink into the sand. But, while he was talking so you didn't notice, he picked up a rubber mallet. Then he said it was not hard to keep buildings on top unless there was an earthquake. When he said "earthquake," he hit the side of the cube with the hammer and all of the buildings disappeared into the sand! (That explained why all of the buildings had wires attached to them so that he could easily pull them out after each demonstration.) The guide then explained the issue of soil liquidation during earthquakes. Foundation expense is probably why the Prudential building was the only big, tall building in Chicago for decades.

The solution is to create a lot of piles in the soil to spread the load and to create a lot of friction. Originally, the piles were driven in the ground. But as the piles became thicker and/or deeper, they could not be forced into the ground. So a bore would be drilled into the soil and filled up with reinforced concrete.  These notes cover the original boring technique. A new technique for creating piles is Auger Cast Piles or Continuous Flight Auger (CFA).

I'm publishing now because I found this article that has done the research for me.
safe_image for Building Skyscrapers on Chicago’s Swampy Soil
[I learned near the end of  this article that the foundations for most of our modern buildings go to hardpan, not bedrock.]
Comments on Daniel's post

David Daruszka commented on Daniel's post
Some older buildings did settle unevenly. Case in point The Gage Building. The right set of bays droops slightly due to settlement.

I remember reading that the foundation for the Kinzie Street RR Bridge was a 30' deep caisson built on top of 90' piles into the bedrock.

I did end up going to Northwestern University to get my Electrical Engineering degree. When I arrived in 1967, they had built the landfill. But the only buildings on it were the planetarium on the northwest corner of the fill and a one-story computer center building that housed our CDC 6400 computer. I knew the planetarium had been torn down because light pollution made it worthless. Looking at a satellite image, it appears the computer center got torn down to make way for the Patrick G. And Shirley W. Ryan Hall. While I was at NU, the new library building was built on the landfill. After I graduated, I heard that the new library was sinking because the architect had not included the extra weight of library books. A quick Google search indicates that this was an urban myth and that the architect was Walter Netsch. [WTTW] This is a common myth concerning many university libraries. [WTTW, snopes, metafilter] I remember watching the TV show of "How I Met Your Mother" when the architect character talked about the risk of making a mistake. As an example, he cited the mistake of a library sinking because the architect forgot the extra weight of the books it held. (The character was Ted Mosby. [StevenDavis])

And now for the collection of photos of drilling the holes for the deep piles.

John Nawakowski -> Forgotten Chicagoto
 Forgotten Chicago
Foundation being laid for Marina City. Chicago,1961
Josh Davis posted
Building 167 W Erie
[Note the auger is laying in the foreground.]
Estructurando posted
Jim Smith posted
J J Novak posted
A video link from the above posting showing "a powerful drilling attachment for deep caisson foundations" in action.

Mike Haggard posted two photos.
Victor Ronquillo Are y'all drilling through granite ?

Mike Haggard posted
Old girl needs some new paint !!
Sean Stewart Very nice, not often you see a 4100 drilling shafts, feel free to share more at facebook.com/groups/pile.driving.and.deep.foundations

This is the first time I have seen long augurs that allows the pile driver to run continuously.

(new window, 6:52)

I never thought about how you start a diesel fuel driver. Watch the second video in this post.

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