Correlation between PI and angle of shear resistance of clays

[Myoho]

Im after the approximate relation between plasiticity index and angle of shear resistance of clays. I am aware of the table produced by Padfield and Mair - is their anything else.

Regards,

Rob K.

 

[Focht3]

Why do you want this type of correlation?



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[GeoPaveTraffic]

Soil Mechanics by Lambe & Whitman has a relationship between the drained friction angle of normally consolidated soils and plasticity index. The original data came from Kenney in 1959.

If you look at this chart you will see considerable scatter in the results. Therefore, extream caution should be used with this relationship.

 

[BigH]

I am presuming that you wish to have this "correlation" so that you can estimate the order of magnitude the expected undrained or effective stress strengths. I strongly suggest that you pick up a copy of Terzaghi, Peck and Mesri. They have, in Articles 19 and 20, a very nice discussion with some correlations. In particular, for clay, after Stark and Eid (ASCE Geotech Journal Vol 120, No. 5 - 1994) they have a nice graph of residual secant friction angle to liquid limits. Similary they discuss various correlation s of Ip to Su/effective stress, etc.

Focht3 posed his questions to you with the view, I believe, that you would use these values for design - for preliminary estimates, I would opine that such correlations - with proper engineering judgment - would be okay - but this does not negate the need to have site specific information with "real" strenght parameters developed from the site.