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Unconfined strength and Net all. bearing value

Unconfined strength and Net all. bearing value

Unconfined strength and Net all. bearing value

What is the relation between these two numbers, if any?

RE: Unconfined strength and Net all. bearing value

If you are running the unconfined compression test, I'll go ahead and assume that you are dealing with a fine-grained (i.e., cohesive) soil.  Therefore, let's discount any contribution from internal friction.

According to the Terzhagi equation, for phi=0 (as appropriate for soils without internal friction), Nc=5.7 so qult=cNc.  For undrained analyses, c=Su (cohesion equals the undrained shear strength.  Undrained shear strength is equal to one-half the unconfined compressive strength.

So, ultimate bearing pressure would be:

qult=5.7*qu/2 or qu*5.7/2 or 2.85*qu

If you consider a safety factor of 3 q-allowable is then equal to:

q-allow=0.95*unconfined compressive strength. Heck that's about like saying the allowable bearing pressure is equal to the unconfined compressive strength!!

Wow!  That was easy, eh?


¡papá gordo ain't no madre flaca!

RE: Unconfined strength and Net all. bearing value

Nice explanation fattdad.

I might add, also check settlement & differential settlement, since it can lower your design allowable bearing pressure.


RE: Unconfined strength and Net all. bearing value

papa gordo, muchas gracias.

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