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# Estimate of Drained Young's Modulus E' of Clay

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## Estimate of Drained Young's Modulus E' of Clay

(OP)
Hi Guys,

Got a problem that has annoyed me for a while. I understand drained Young's Modulus E' of clay can be obtained from Oedometer consolidation test in the Lab; and there are also many published correlations between CPT qc, relative density and E' for SAND. However, I was wondering if there way to estimate E' of CLAY from CPT, SPT or other methods rather than laboratory testing? This is because we don't always have Oedometer or 1D consolidation test data for every single project...

### RE: Estimate of Drained Young's Modulus E' of Clay

You don't typically derive soil modulus from the odometer.  You derive soil modulus from the triaxial test or in the field, I like the dilatometer.

f-d

¡papá gordo ain't no madre flaca!

### RE: Estimate of Drained Young's Modulus E' of Clay

Here is the equation for deriving E' for clay from SPT N;

E' = 1 / (450 N) m2/KN
= 1000 / 450N m2/MN.

Note that SPT N is uncorrected.

This is equation is after Stroud and Butler, 1975.

### RE: Estimate of Drained Young's Modulus E' of Clay

There are a few published correlations for constrained modulus and qc for clays as well...

What I use:

Sanglerat 1972 is pretty much used in Europe for silty clays

Mayne et al. 1990 for the ECPT

### RE: Estimate of Drained Young's Modulus E' of Clay

No matter how, CPT or SPT can only give a semi emperical correlation of the stiffness of the soil. As the clay's behaviour is very complex during CPT or SPT penetration in clayey soil,it can not be easily ascribed as compression or shear or something else.
If you want to get more reliable results, oedometer test is neccesary.

### RE: Estimate of Drained Young's Modulus E' of Clay

How does one get Young's mod from an oedometer?  Don't you have to ASSUME Poisson's ratio because of the lateral constraint (uniaxial strain vs uniaxial stress)?

### RE: Estimate of Drained Young's Modulus E' of Clay

To qhtony:E' means constrained modulus or not? I thought it is. If not ,you could only rely on triaxial tests CD test.

### RE: Estimate of Drained Young's Modulus E' of Clay

(OP)
To paganel: for the use in my model, it is a constrained modulus. you're right. triaxial CD with specified cell pressure will give me the E' I want.

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