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RE: Footing Retrofit/Replacement Ideas

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I've gotten better than 5 to 20 kips in the past.  The idea of the
micropiles is no different than any other deep foundation that will
carry the loads down to bedrock, disintegrated rock, or other dense
soils that exist well below the current shallow footing bearing.  I
haven't personally used upwards of 300 kips, but I've had in the range
of 80 to 100 kips in this region.

Eric R. Ober, PE, SE
Associate
Holbert Apple Associates
Olney, Maryland
 

-----Original Message-----
From: Eli Grassley [mailto:elig(--nospam--at)psm-engineers.com] 
Sent: Monday, February 13, 2006 2:49 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Footing Retrofit/Replacement Ideas

>J. Gomez wrote:
> Can have capacities in excess of 300 kip each depending on the
> subsurface conditions.


I don't think quoting a capacity of 300kips for micropiles is doing
anybody
any favors here.  A more realistic capacity to expect is on the range of
5-20 kips.  If your soil is so dense that you can get 300kips out of a
micropile, the you probably wouldn't be having any problems with your
foundation in the first place.

~~ Eli ~~


-----Original Message-----
From: Jesus Gomez [mailto:jgomez(--nospam--at)schnabel-eng.com] 
Sent: Friday, February 10, 2006 6:25 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: Re: Footing Retrofit/Replacement Ideas

Micropiles are extensively used for this application. They can be
drilled
from the ground surface, either through or beside the existing footing.
Can
have capacities in excess of 300 kip each depending on the subsurface
conditions. 

If drilled through the footing, they can be bonded directly to the
footing
(they are grouted with neat cement grout). Bond stress would be about
100
psi allowable in your case ( difficult to clean corehole through
footing).

If installed beside the footing, can just tie to pier through steel
beams.
In this case, they can be preloaded.
 

-----Original Message-----
From: Daryl Richardson
To: seaint(--nospam--at)seaint.org
Sent: Thu Feb 09 21:08:14 2006
Subject: Re: Footing Retrofit/Replacement Ideas

Sir,
 
        I have two possible ideas for brainstorming consideration only.
I
would only use these with the advice of a geotechnical engineer.
 
        First: if the soil upon which the footing is permeable an
application of pressure grouting may consolidate the soil sufficiently
to
increase the allowable bearing capacity and make any other repair
unnecessary.
 
        Second: I once provided a second opinion for a scheme to remove
contaminated soil from underneath a number of row houses.  Under this
scheme
small diameter "mini piles" about 2.5" to 3" in diameter were jacked
into
the ground at about 4' centers around the houses and bolted to the
foundation walls allowing petroleum contaminated soil to be removed from
under the houses (including basement slabs on grade) and replaced with
clean
material.  This was a large budget project; you'd need all of your
fingers
(plus some toes too) to count the cost in millions of dollars.  This
project
was completed successfully.
 
        In your case four such piles, either placed through holes cored
in
the footing near the column or installed at the edges of the footing
might
give you a combined pile/spread footing foundation suitable to carry the
load.
 
        Just a couple of thoughts that may or may not be helpful.
 
Regards,
 
H. Daryl Richardson

	----- Original Message ----- 
	From: Eknrinc(--nospam--at)aol.com 
	To: seaint(--nospam--at)seaint.org 
	Sent: Thursday, February 09, 2006 7:50 AM
	Subject: Footing Retrofit/Replacement Ideas

		I have a project which limits me to having to upgrade a
concrete pad footing bearing area. The existing footing is 4' square x
12"
deep. Here are my initial ideas:
	 
	1. Underpin (this requires shoring supported beams)
	2. Demolish and replace (this requires shoring supported beams)
	3. Pad extension on two sides (may run into existing
reinforcement
for continuous flexural reinforcement installation/coring)  
	 
	Any other ideas?
	 
	Thanks in advance.

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