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I would need your help concerning the Triaxial. Since I need a
specific value of final porosity, I am trying to do something in your code but
without success (BTW, I DON'T want to modify your code, if it will work I will
manage to add a flag or something like that).
No problem. Just keep me updated so I know what happens in files.
so basically in the line
(1) it is like saying "cycle" without expanding if the value of Unb force is
too high. Unfortunately "cycling" doesn't help (why? Should it?), the computed
unbalanced force is always very high and around 1.
There is nothing "bad" in keeping a constant radius until unbF is small.
If the unbalanced force does not approach 0 with cycles "_supposed to
be_" doing nothing else than dynamic integration, there is clearly
something wrong. The timestep is not 0?
The only problem I see in your approach is you force the porosity you
want, which will result in very big overlaps and high stress most
likely. The porosity should be the result of a "realistic" packing
Could you give me any
suggestions or directions how to do that? I mean, how to fix the value of final
Keep a constant stress and decrease friction a little bit at each step.
The packing will self-reorganize, and porosity will decrease. Save the
packing state when porosity value cross the value you want.
You can use this function to modify friction :
void TriaxialCompressionEngine::setContactProperties(Scene * ncb, Real
frictionDegree)//I really mean "use", not copy ;)
All you have to do is a loop that will keep assigning frictionDegree
each n=~10 steps, with a decreased frictionDegree each time.
Note that big porosity variations usually occur with small values of
friction, in the range 0° < f < 5°.
I have got that having a specific PSD and a
friction angle we can get only one possible value of final porosity (or a very
small range of it) and that's true with the DEM (cause we are dealing with
spheres and not irregular shapes) but to me it is always possible to say that
for the same PSD I would like to run the Triaxial with an higher porosity
(higher than that maximum dense packing I get with this method either with
compaction or expansion).
What is small range? I tried that after your message and I got different
poro from different friction.
From: Chiara Modenese, 2010-01-19