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[Robert Caulk <question679566@xxxxxxxxxxxxxxxxxxxxx>]

Question #679566 on Yade changed:
https://answers.launchpad.net/yade/+question/679566

Robert Caulk posted a new comment:
Thank you for the MWE

>> this is a method to simulate undrained condition in triaxial test
without fluid.

Do you have a reference for this?

>>This is a purely conceptual problem. In lab you can impose total confining
stress, yes, but the effective confining stress is changing nevertheless.
In DEM you don't simulate the fluid, so which one do you record? Effective
or total?

Am I mistaken or should strain rate technically depend on maintaining
pore pressure equilibrium for a consolidated undrained test? In that
case the effective confining stress should remain constant. Right?

Correct me if I am wrong, but the assumption that your volume will not
change by simply applying an axial strainRate and lateral -strainRate/2
is incorrect for a dry cubical packing of frictionally interacting
spheres. Consider the role of the fluid pressure in an undrained
triaxial test, it does not allow the force due to friction between sand
grains to increase. In your case, the particles continue to
"consolidate" (overlap) since the pore pressure is not modeled. If they
are consolidating, the volume is changing and the packing is not
expanding outwards with your walls, resulting in a decrease of confining
pressure. I don't see how this model could represent the consolidated
undrained shear strength.

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