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Re: [Question #172107]: Difference between volumetric strains evaluated by strains and void ratio

 

Question #172107 on Yade changed:
https://answers.launchpad.net/yade/+question/172107

    Status: Open => Answered

tranviet proposed the following answer:
Hello Janaka,

I have followed your discussion about the volumetric strain these days,
and I think I can help you:

1. How many particles did you use in your simulation? if you use too few
particles, I am sure that you will have different answers for two
methods of calculation. I think everyone here can know the reason.

2. I have run thousands of triaxial test simulations until now, and I
can confirm that there is nothing wrong with the answer if you increase
the number of particles (here in my simulation  is 150,000). You cannot
get correct answer if using less than 1000 particles, the example of the
triaxialtest from the source code is just to help us know how the
problem is solved.

In one of my simulation, and at a typical step:

-Initial void ratio: 0.649 (porosity = 0.3937)
-Current void ratio:  0.661 (porosity = 0.3978)
-Volumetric strain by method 1: (0.661-0.649)/(1+0.649)*100 = 0.6885 (%)
-Volumetric strain by method 1:
      e11 = -0.0217, e22 = 0.0264, e33 = -0.0115
     -> (e11+e22+e33)*100= 0.6781 (%) (change to positive value for easy use)

I can send you the .xml file as well as the output files if you are
interested.

Cheers,

Viet

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