2D consolidation

Hello,

I am trying to consolidate the 2D packing using TriaxialStressController and trying to track a porosity change.
Based on my calculation, Yade is able to recognize the 2 dimensional particle because I have got the same mass of particle by assuming the density of particle as YADE did.
Now, I am trying to compare the porosity between my calculation and YADE using triax.porosity and there is a discrepancy.
I am not able to find out the reason.
Alternatively, I am trying to track a volume change using boxVolume in the TriaxialStressController and it also give me a discrepancy.
For example, if I set the 2D packing like (Vector3(10.e-3,0,0),Vector3(10.e-3,10.e-3,30.e-3)) , the volume or area of packing should be 3.0e-4. right? However, YADE using boxVolume got me 1.xx e-7.
Can anyone tell me what I am missing?
Thank you for your help!

Seungcheol