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RE: Auger Cast Piles

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The "concrete" is more like "grout" approximately 8" to 9" slump with pea
gravel as the largest aggregate I've seen used. After the hole is augered,
the grout is pumped through the hollow auger stem under positive pressure as
the auger is withdrawn.  This positive pressure is maintained all the way to
the top of the pile.  After this, the cage is craned into position and
lowered into the grout.  On jobs we have done, the contractors use wire
"bulbs" or "balls" tied periodically to the cage to center the cage in the
grout. The cage isn't perfectly centered I'm sure, but structural
engineering isn't a perfect science, right? :^)

We have used 18" "auger cast piles" 90' long and approximately 80 to 90 ton
capacity per pile.  I'm not sure what the limits on the depth of these pile
are, maybe someone out there can comment on that.  My guess is that it is
probably a function of available drill rig size and auger length.

If piles are subject to uplift, bundled or single bars are run full pile
length down the center of the cage, and the cage is typically down to a
depth below where moments go to approximately zero.  The cage depth depends
on geotechnical criteria, whether the soil is liquefiable, etc. etc.  You
definitely want good geotechnical information for design and your geotech on
site full time to observe and monitor the pile installation.

Hope this helps.
Jim Hagensen, SE  

-----Original Message-----
From: George Richards, P.E. [mailto:george(--nospam--at)BORM.com]
Sent: Friday, September 01, 2000 8:46 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Auger Cast Piles


If I may ask a second set of questions.  How do we get a gage of steel down
into a hole that has already been filled with concrete?  Then when the cage
is in how do you know you maintained 3 or 4 inches clear to soil?  How deep
can one drill to?  

Thank you.  George Richards, P. E.

-----Original Message-----
From: James Hagensen [mailto:JHAGENSEN(--nospam--at)HNTB.com]
Sent: Thursday, August 31, 2000 9:54 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Auger Cast Piles


We have never used augercast piles smaller than 14". A better size and the
size we have used the most is 18".  This size worked best since we used the
piles in seismic zone 3 and had lateral loads in the piles.  (At 14"
diameter you can' get much of a cage in the top of the pile allowing for 3"
clear around the cage.)  Bending moments and ductility requirements in the
upper portions of the pile greatly effected and often controlled the design.


Jim Hagensen, SE

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