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Re: Strengthening soils under existing footing?

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You may consider an option of driving a steel pile adjacent to the footing and attaching the footing to the pile. That is, if it is feasible to drive a pile.
The feasibility of injection grout to improve soil capacity as well as the cost to do it depends on the soil type. While a sandy soil will absorb quite a lot of grout, a clayey soil may refuse to accept anything. You may check with a local geotech. If you know the soil type, Baker Hughes might be able to suggest a cost effective solution. It is one of the experts in ground modification techniques.

Jim Wilson <wilsonengineers(--nospam--at)> wrote:
Has anyone considered a way to strengthen the soils under an existing footing without disturbing much of the surrounding?  I am envisioning pressure grouting through a 30" x 30" footing to the soil below to effectively increase the bearing area.  Hmm...
The original design drawings ca. 1975 state a 4000psf soil capacity.  The owner wants to add a penthouse/roof structure, but the soil bearing pressure is limiting the ability to do so.  Its hardly practical to widen the footings and add new columns centered on the new improved/footing.
Is grouting effective in this case, and is it even cost effective?  Any thoughts?
Thanks in advance,
Jim Wilson, PE
Stroudsburg, PA

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