Subsurface Exploration 1

[Alireza1945]

I wanted to know why we dont correct SPT number due to overburden pressure in cohesive soil .
Is it because of Phi=0 concept ?
Im really stucked here.
Tnx in advance.

 

[dgillette]

It depends on what you are trying to find.

In granular soils, we usually adjust blow count for overburden stress if we are trying to predict relative density or some related property like cyclic resistance ratio because, for a given relative density, the blow count increases with confining pressure. For a claylike soil, the blow count varies roughly in proportion with undrained strength, which, for a given soil and void ratio, doesn't vary much at all with overburden pressure.

There may be other uses that do/don't require normalizing, opposite of typical practice, but I can't think of them right now.

That help?

 

[Alireza1945]

Thank you very much.
Roughly exactly what I need to know:d