## Modulus of Elasticity E Values

## Modulus of Elasticity E Values

(OP)

Hello engineers,

I am working on the geotecnical report for the foundation of tower.

I use sigma W in order to estimate inmediate settlements.

As you may know, you need to enter the Modulus of Elasticity values (E) and poisson, for each soil layer.

I have some Modulus of elasticity values according to the SPT-N values. From 0-4, 5-10, 11-30, 31-50, 51-100, >100. It doesn't matter if it is a cohesive or cohesionless soil.

I am not sure if this is ok. I would like to confirm with any of you with some experience what are the best / most useful Modulus of elasticity values geotechnical engineers use nowadays.

Thanks

I am working on the geotecnical report for the foundation of tower.

I use sigma W in order to estimate inmediate settlements.

As you may know, you need to enter the Modulus of Elasticity values (E) and poisson, for each soil layer.

I have some Modulus of elasticity values according to the SPT-N values. From 0-4, 5-10, 11-30, 31-50, 51-100, >100. It doesn't matter if it is a cohesive or cohesionless soil.

I am not sure if this is ok. I would like to confirm with any of you with some experience what are the best / most useful Modulus of elasticity values geotechnical engineers use nowadays.

Thanks

## RE: Modulus of Elasticity E Values

I would expect the following:

silt and clay....5 to 7 ksi

sand...10 to 15 ksi

clayey sand...15 to 20 ksi

## RE: Modulus of Elasticity E Values

This being said, the best in-situ method to get deformation moduli is the pressuremeter because it is the only test where you have a pseudo-elastic loading phase.

CPT in sands will allow you to get reasonable values as well but not in clays.

Correlations between E ( pressuremeter modulus ) and N is as follows :

N/E for clays : 0.8 to 1.1

for silts : 3

for sands : 2 to 6

You will obtain the deformation modulus from the pressuremeter modulus by multiplyng it by 3 for sands, 2 for silts and 1.5 for clays.

Just be careful with correlations : you will only get orders of magnitude. Do the proper testing to get the right input data.

## RE: Modulus of Elasticity E Values

Unfortunatly we don't have the appropiate instrumentation to obtain the modulus of elasticity.

I knew there was something wrong about our E values. I will follow your advise.

What would you guys expect for silty sands (sm) and silty gravel

(Gm) as the site I am working on is mainly composed of these soils.

Or is there any reference you recommend I should get?

Thanks again

## RE: Modulus of Elasticity E Values

## RE: Modulus of Elasticity E Values

I have always used E = 400 to 600 times the Su value for ohesive soils. According to Budhu's "Soil Mechanics and Foundations" book 2nd edition, page 605, cohesionless soils have the following E values (secant values):

Loose sand = 400,000 psf

med-dense sand = 800,000 psf

dense sand = 1,600,000 psf

Try to get your hands on a copy of "Manual on Estimating Soil Properties for Foundation Design", 1990 by Mayne and Kulhawy. It maybe online somewhere.

## RE: Modulus of Elasticity E Values

You can find Paul's downloadable papers at:

htt

## RE: Modulus of Elasticity E Values

## RE: Modulus of Elasticity E Values

## RE: Modulus of Elasticity E Values

## RE: Modulus of Elasticity E Values

## RE: Modulus of Elasticity E Values

Due to the lack of accuracy using correlations, FEM analysis could lead to different results.

This problem gets even more serious when based on the settlemnt values you have to provide recommendations. For example using my E values due to the high settlement results I get, I could recommend any type of deep foundations, on the other hand if someone gets lower settlement values he could recommend anything else or maybe nothing as the settlments might be less than the allowables.

At the end, all this means money to the client.

## RE: Modulus of Elasticity E Values

Pelelo's soils would be suited to the AASHTO, 1996 correlation: E=0.4÷0.7n [MPa], but I find it way too conservative.

Lately I've been doing quite a few investigations on existing buildings, damaged by an earthquake, but in good conditions prior to the quake.

The above correlations woudl indicate likely settlements problems, whereas these were not observed.

I tried to compare results from geophysical surveys (Vs profiles), going from the dynamic E degraded to the secant E and sometimes it 'feels' better, even though apaprently under-conservative.

Right now I'm using Nspt-Gmax correlations, which afterwards I degrade to Gsecant and transform into Esecant knowing the poisson module .

It sounds convoluted, I know, but this way I get results which would appear to be more realistic.

That is, the soil under houses which had no settlement problems comes out pretty good and not pretty 'crappy'.

Your opinion about that?

## RE: Modulus of Elasticity E Values

Some of'em have filters which allow you to apply soil-specific correlations, plus you have output histograms where you have the whole 'scenery', have a feel for the possible range and might eventually decide to take the median value of the parameter.

## RE: Modulus of Elasticity E Values

http://www

There's also other information on elastic moduli for rock, etc., scattered in the text.

That having been said, they're still correlations, with the caveats that BigH mentioned.

http://www.pz27.net

## RE: Modulus of Elasticity E Values

Richard A. Cornelius, P.E.

WWW.amlinereast.com

## RE: Modulus of Elasticity E Values