Yade

Modelling triaxial test of cemented sand

Asked by Popo

Hello all,

I 'm a new user of Yade and I would like to perform simulations on the triaxial test of cemented sand, i,e. the grains have a specific cohesion with each other. I had gone through the example scripts (triax-tutorial. test/triax-cohesive), but I am not sure how I could specify the cohesion(normal and shear, maybe the in the CohFrictMat material properties?)
between the grains based on a normal distribution in the Cohesive Frictional contact law.
I am also looking at the Jointed Cohesive Frictional model as I could specify the bond strength between the grains. The end goal is to see the behaviour of sand with different distribution of cohesive strength between the grains, therefore I would like to have your advise on which contact model would suit the purpose best.

Thank you very much

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Jérôme Duriez (jduriez) said : 		#1

Hi,

Both mentioned models let indeed specify cohesive strength for interaction.

In both cases, the interaction cohesive strength (like any other interaction properties, as a general rule in Yade) are derived from the Material parameters (either JCFpmMat or CohFrictMat) through corresponding "Ip2", see Ip2_JCFpmMat_JCFpmMat_JCFpmPhys or Ip2_CohFrictMat_CohFrictMat_CohFrictPhys.
See also the doc [1,2] for general explanations about these "Ip2".

This being said, an exact understanding of the differences between the two models requires some time to fully grasp each one in details.
It has also been often discussed here on the mailing list (you may browse the archives through [3]).

As an incomplete answer, let me say for instance that
- JCFpm model (designed with fractured rock in mind) let one easily play with the interaction normal (for it to be different than the normal deduced from the particle spherical geometries) and automatically takes the normal overlap at interaction creation as "equilibrium overlap" corresponding to zero normal force. Depending on your simulation workflow, this equilibrium overlap may thus be non-zero

- CohFrictMat (designed with cohesive granular materials in mind) does not include the two above features, and includes "rolling resistance" with interaction torques opposing changes in particles relative orientation.

[1] https://yade-dem.org/doc/introduction.html#dispatchers-and-functors
[2] https://yade-dem.org/doc/user.html#ip2-functors
[3] http://<email address hidden>/

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