Problem description

The volumetric strain as calculated in Output and Curves is based on the definition according to the small deformation theory:

When using Updated Mesh in Plaxis, the volumetric strain should be defined according to the large deformation theory, taking geometric changes into account:

However, when displaying results for an Updated Mesh calculation in PLAXIS 2D 2011 and PLAXIS 3D 2011, the volumetric strain is still presented according to the small deformation theory.

This is fixed since PLAXIS 3D 2011.01

Solution

It is possible to obtain the correct volumetric strains when using Updated Mesh: copy the table of cartesian strains and paste it in a spreadsheet program like Microsoft Excel. Here you can calculate the volumetric strains by using the above mentioned equation.

Note that the volumetric strain is presented correctly when not using Updated Mesh.