Problem in keeping the volume constant during triaxial undrained test

I am trying to keep the volume of the triaxial specimen constant throughout the test to maintain an undrained condition, but it’s not working. In 2D, the same logic works well, but it fails in 3D to maintain the volume.
volume.txt (2.4 KB)

Dear Mujeeb, I cannot debug your FISH function. The code seems to be working. If it works in 2D, then you must have a small error in the 3D case. Be careful and consistent when defining volumetric strain in 2D and 3D. This quantity is defined for 2D and 3D in Section 5.1 {Stress, Strain and Porosity in the Material} of the {Material Modeling Support for PFC [mmPkg9.3]} memo that can be downloaded from the link: {Material-Modeling Support for PFC | US Minneapolis - Itasca Consulting Group, Inc.}. You should consider using this package to perform triaxial tests on PFC material.

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