## Estimating friction angle of clay

## Estimating friction angle of clay

(OP)

Hi

Is it possible to estimate friction angle of clay for drained stability calculation? I heart that there is some software which is able to estimate friction angle based on clay-size fraction and some other parameters.

Is it possible to estimate friction angle of clay for drained stability calculation? I heart that there is some software which is able to estimate friction angle based on clay-size fraction and some other parameters.

## RE: Estimating friction angle of clay

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## RE: Estimating friction angle of clay

www.PeirceEngineering.com

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

I also agree with Ron on those values !

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

http://www4.hcmut.edu.vn/~cnan/Principles%20of%20g...

It is a similar graph to what is shown in L&W.

## RE: Estimating friction angle of clay

When i check a PI of 20% with the BS8002 equation I posted above it gives a Φ of 26 degrees.

Be interested to check the L and W graph with the BS8002, the link you posted doesnt work. Could you post it again.

## RE: Estimating friction angle of clay

I think that since the equation from BS8002 is based on critical state soil mechanics, from the stress-strain curve, the strength at constant volume is referred at a point of "lower strengths" (end of the curve) and this may be the reason why the BS equation results in lower phi' values.

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

Ive checked it again for a PI of 30%

L & w gives a Φ = 27°

BS8002:2015 (my first equation) gives a Φ = 24°

BS8002:1994 (pic below) gives a Φ = 25°

Not much in it really...

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

I would be interested to see if anyone uses any correlations between Cu and Φ....

## RE: Estimating friction angle of clay

Don't forget that your groundwater assumptions and design factor of safety are just as important as your strength assumptions.

Lest of luck.

Mike Lambert

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

Make sure however you are not facing a residual strength situation

## RE: Estimating friction angle of clay

in the instance of clay, you have softening effects. Such effects are rarely captured in in-situ testing or in laboratory testing of undisturbed samples. In those instances, the strength is informed by conditions that may not be available during the design life.

Softening effects occur from freezing/thawing and wetting/drying. Such changes can take years (decades?) to develop. Using softened strength is prudent in long-term design.

If I had a project where such strength is critical, I'd likely use Stark's correlations. I'd also likely take a bulk sample, hydrate it to the liquid limit, normally consolidate it to three confinements and run my own fully-softened DDS test. Stark's correlations are based on the torsional shear test and I'd want to know if my relations to clay and PI related to the DDS as Dr. Stark's correlations related to torsional shear.

I'm a skeptic that way. . .

f-d

ípapß gordo ainÆt no madre flaca!

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

f-d

ípapß gordo ainÆt no madre flaca!

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay

## RE: Estimating friction angle of clay