Estimating Eu using Su for clay?

[qhtony]

Hi guys,

I have been scratching my head off trying to find out the relationship between Eu (undrained Elasticity Modulus of soil) and Su (undrained shear strength of clay). However, literatures do not give a straight forward relationship between these two. Most of them are Eu=K*Su, but the K usually depends on various factors such as PI and OCR etc and can be read from charts.

I am wondering, say for normal consolidated clay, is there a simply relationship that I can determine Eu using Su??

Thanks,

 

[fattdad]

How will the value of soil modulus be used when the correlation (if the correlation) is obtained? It seems for a normally consolidated clay, you'd be more interested in the 1-D consolidation characteristics.

f-d

¡papá gordo ain’t no madre flaca!

 

[qhtony]

Hi f-d,

The ultimate goal is to find out Kh (horizontal modulus of subgrade reaction), which is dependent on d, Eu and poisson's ratio based on Vesic (1961)'s elastic theory.

For clay with known undrained shear strength, using the formula above, Kh then can be determined.

So is there any correlation between Eu and Su ?

 

[BigH]

There has been many published relationships - Bowles has them summarized. Other texts, too. I don't want to quote off the top of my head - all my references are at work - although 250 to 400xSu pops;/i] into my head (but the actual correlations depend on plasticity and consistency. As with any 'correlations' you should try to research the types of soils it really applies to and confirm that it makes sense for you. You might look at Tomlinson's piling book - he has a very nice section on the subject.

 

[qhtony]

Thanks BigH, I happen to have Tomlinson's book at home... Will have a look.

cheers,

 

[fattdad]

is this for research or is there an engineering application? That's what I was wondering. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[qhtony]

Hi F-d, it's a half-half. It's just my own interest in this subject. We've got software to estimate the deflection of lateral loaded pile at work. But I'm trying to develop a simple excel spreadsheet with minimal input of geoetech parameters (i.e. Su, PI) to estimate deflection. And the K value is one of the intermediate paratmers which relates back to Su.

 

[BigH]

ghtony - check out the link I got from googling google images! You can use the link to download the paper.

http://www.ejge.com/1997/Ppr9707/gif/Fig3.gif

 

[qhtony]

Thanks BigH. This is very useful.