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Drained conditions on slope stability

Drained conditions on slope stability

Drained conditions on slope stability

(OP)
Do you know if there is any empirical correlation, paper or research on obtaing c' from SPT data.  If you can give some light about; i'm trying to do a slope stability analysis.  I know how to estimate peak phi, but, how can I estimate c'.  I don't think it should be equal to zero when working with cohesive soils, Medium to stiff cohesive soils (MH as per USCS), when drained condition should govern.  Am i right?

RE: Drained conditions on slope stability

Remember that c' - phi' is a mathematical model.  In almost all cases, c' really does equal zero at the appropriate normal stress levels - but at normal working stress levels, in forming your failure envelope, you do have, what I generally call, an apparent cohesion. (in residual and critical states, it is zero).  There is, to my knowledge, no relationship that has ever been established between c' and SPT.  Sorry.

RE: Drained conditions on slope stability

(OP)
Thanks for your opinion. Thought the relationship did not exist because I have never found it.  IS apparent cohesion a standard value range?, say 50 to 200 psf?  This is the range I usually select.  Is there any maximum apparent cohesion?  I found once two publications that recommended c' for compacted soils.  Right now I may tell one of them was a NAVFAC but I cant tell exactly cause I'm at home.  These recommended c' ranging from about 50 to 150 psf for compacted clays.  

RE: Drained conditions on slope stability

you may need to look into undrained condition for cohesive soil.

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