Poisson's Ratio & Volumetric Strain

[scottm8]

One of our geotech subs has included a graph of axial strain vs. volumetric strain in a triaxial CD test report. I need to calculate poisson's ratio for the material, but I don't think volumetric strain vs. axial strain depicts the same relationship that poisson's ratio is meant to describe (lateral strain vs. axial strain). Is this correct, or is there a way to calculate poisson's ratio?

Thanks!

 

[dgillette]

Sure. Vol. strain = sum of X, Y, and Z strains. X and Y strains are lateral, presumably equal. Z is axial, and has the opposite sign.

Vol strain = Z strain - 2 * nu * Z strain