How to choose value of possion ratio for low permeability shale?

[roudan]

HI
I am doing modelling shale deformation using Abaqus. I need to input possion ratio. I am not sure what kind of value do I input?

Here are my thoughts which confused me.

For low permeability shale, if triaxial test is conducted under undrained condition, the poisson ration will be 0.5 since it is undrained.
if the triaxial test is conducted on drained condition, the poisson ration will be less than 0.5, like 0.3-0.4.

Now for Abaqus modelling using SOIL analysis type, I will model both effective stress and pore pressure change with input of permeability. What Poisson ratio do I input? Drained or undrained?

Thanks.

 

[rb1957]

why not both … drained and undrained … to see if this has a bearing on the results ?

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