Correlation between Eu and Su

qhtony (Civil/Environme)
8 May 09 8:30
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 (Geotechnical)
8 May 09 9:45
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



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qhtony (Civil/Environme)
9 May 09 6:51
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 (Geotechnical)
9 May 09 10:06
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 [i]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.