# PLE forum

Full Version: Poisson ratio of the soil in the Soil Model Wizard
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
Currently the Soil Wizard uses the default value 0.35 for the Poisson ratio in th calculation for KLS (trenchless).

This ratio is given by default by the Dutch Code NEN 3650-1, but this value is not accurate for different kind of soils.

This is the accurate formula:

[attachment=258]
If you use the formula for the Poisson ratio nu, you obtain the values 0.55 - 0.70 for the common range of phi = 10 - 35 degrees.
The value 0.35 mentioned in the NEN 3650 code falls far outside this range and therefore can not be considered as a 'default' value to my opinion.
It is questioned whether the mentioned formula for nu should be applied in the Schleicher formula.
In a paper on the website of Delft Cluster dealing with the Schleicher approach and finite element calculations for a horizontally drilled pipeline the nu values 0.35 and 0.45 have been used for phi ranges from 0 to 35 degrees.

I have replaced the formula in the first post, a mistake was made in the formula.

So for phi 10 - 35 degrees nu varies from 0.45 - 0.30.
We are currently updating the Soil Model Wizard and therefore would like to know the source of the formula for nu provided.
Th Wizard has been based on the NEN 3650 standard and modifications should be based on known and proven sources.
If we receive such information, we are willing to incorporate the formula into the Soil Model Wizard.
(02-11-2015, 03:04 PM)ir KW Radder Wrote: [ -> ]We are currently updating the Soil Model Wizard and therefore would like to know the source of the formula for nu provided.
Th Wizard has been based on the NEN 3650 standard and modifications should be based on known and proven sources.
If we receive such information, we are willing to incorporate the formula into the Soil Model Wizard.

Rien,

See for the source in page 5 of the attached PDF. I have rewritten the formulae from the soilmechanic book from TU Delft.
Shaswin,
Thank you for providing the acknowledgement of sources.
We will take the formula into account when updating the Soil Model Wizard.
In the upcoming release the poisson ratio is calculated using the formula (for the trenchless situation). The help file is updated accordingly.