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Re: Footing Retrofit/Replacement Ideas

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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 -----
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.