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When using a FlowEngine, is the confining pressure of the triaxial test an effective stress?

Asked by Zhicheng Gao

In the oedometer.py[1], the confining pressure is set by triax.goal1=triax.goal2=triax.goal3=-10000 and FlowEngine is active. In this case, is confining pressure effective stress？
Thank you!

[1]https://gitlab.com/yade-dev/trunk/blob/master/examples/FluidCouplingPFV/oedometer.py

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Robert Caulk
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Jérôme Duriez (jduriez) said : 		#1

I would say it is the total stress (in your [1] example, triax.goal* is constant but strain evolves during the consolidation phase, no ?) but I'm no longer that sure.
Maybe the answer is in Catalano PhD manuscript (in a § about sample boundaries treatment ?) / will come from someone else.

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Best Robert Caulk (rcaulk) said (last edit ): 		#2

I confirm Jérôme's instinct. "Effective stress" depends on perspective (i.e. effective stress on which grain??). Application of an "effective stress" from an external loading with TriaxialStressController would require making generalizations about pore-pressure inside the specimen. Which seems like a futile process for any dynamic flowengine scenario with non homogenous pore pressures.

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Zhicheng Gao (zhichenggao) said : 		#3

Thanks Robert Caulk, that solved my question.