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Re: augered piles

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I would NOT say that it is impossible to get moisture in the full 20' of 
expansive soil.

Since soil moisture accumulates under a building, stone, rock, piece of 
plastic, piece of cardboard, etc. in even the driest of conditions, the 
moisture under a building can accumulate gradually and dry out so slowly that 
it can be characterized that moisture containing soil under a building 
*never* drys out, yes, the entire 20' layer of expansive soil can be 
subjected to increased moisture.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Steven A. wrote:

. > Roger,

. > Assuming your 20' depth of expansive soil is bone dry, could you get 
. > moisture down that deep and fully
. > distributed through the soil mass to realize its full (theoretical)
. > expansiveness?

. > Steven A.
. > Los Angeles

. > Roger Turk wrote:

> Mike,
> You may be anchoring the piles to rock, but the expansive soils may blow out
> your slab!
> IMO, the expansion index is meaningless for structural engineers.  The
> information that *I* need is the confinement pressure that is necessary to
> *prevent* expansive soils from expanding.  If the confinement pressure is
> 5 psf, I am certain that I can handle that.  However, if the confinement
> pressure is 5 TONS per square foot, there is nothing that I can reasonably
> to accommodate that.
> (If your expansive soils have a 1 percent expansion potential, but you have
> 20 feet of expansive soils, the 1 percent results in a 2.4" expansion.  If
> the confinement pressure is 1,000 psf, can the slab resist that kind of
> force?)
> A. Roger Turk, P.E.(Structural)
> Tucson, Arizona

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