How to estimate Modulus of Elasticity and Poisson Ratio of Soil?

[JoeH78]

Dear Community Members,

Regarding the soil report we would to further study how the results of Modulus of elasticity and Poisson ratio is found by geotechnical engineer. So based on that I'd like to know how do you guide to estimate the modulus of elasticity and poisson ratio of soil, Where characteristics of soil is given below:

1.Strata 2.5 mt Structural Back fill where Soil MoE is estimated as E_s= 100MPa.
2.Strata 3.5 mt Clay N30 (SPT) = 15 and where MoE is estimated as E_s= 28MPa.
3.Strata 9.0 mt Clay N30 (SPT) = 27 and where MoE is estimated as E_s= 59MPa.
4.Strata 15.mt Clay N30 (SPT) = 40 and where MoE is estimated as E_s= 160MPa.

My intention to find the possion ratio is: It may be a possible that Modulus of Elasticity is related to possion Ratio, normally it is as by the rules of traditional linear elasticity but since the soil is question here and regarding the Bowles suggestion Chapter 5.8 ( Table 5-6) Equations for stress-strain modulus Es by several test methods. MoE may not have relevance to Possion Ratio.

I'll appreciate your guidance ?

 

[IDS]

You should ask the geotechnical engineer who supplied the data.

You should also be aware that soil does not have a single modulus of elasticity. It varies with duration of load, deformation, depth, loading and unloading and reloading, and moisture content, amongst other things.

If the soil stiffness affects the results of your analysis significantly you should repeat the analysis with lower and upper bound values, and use the worse results.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[oldestguy]

This old guy has been around for a long time. The parameters mentioned usually were meant for other materials, not soil. Sounds fishy. There are other parameters that are well documented as to usage, but not these.

 

[GeoEnvGuy]

The information provided states N30, inferring a 30% hammer efficiency, this is not common. Modulus of elasticity and a lot of other parameters are typically correlated to N1(60), or N60 for some older datasets. Your N values in clay appear high in general and appear to be increasing with depth at a rate higher than normally consolidated clays.


Also if your interested getting a decent estimate of Poisson ratio. Shear wave tests performed by CPT machines can give you a better indication.