Unconfined strength and Net all. bearing value Unconfined strength and Net all. bearing value WWTEng (Structural) (OP) 2 Nov 11 11:23 What is the relation between these two numbers, if any? RE: Unconfined strength and Net all. bearing value fattdad (Geotechnical) 10 Nov 11 13:11 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*quIf 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?f-d ¡papá gordo ain't no madre flaca! RE: Unconfined strength and Net all. bearing value FixedEarth (Geotechnical) 11 Nov 11 14:36 Nice explanation fattdad. I might add, also check settlement & differential settlement, since it can lower your design allowable bearing pressure. www.FoundEng.com RE: Unconfined strength and Net all. bearing value WWTEng (Structural) (OP) 12 Nov 11 20:07 papa gordo, muchas gracias.