Finding vertical stress inside the soil.

Question

Hi, 
 I am trying to model the loading of a steel plate placed on a dry sand bed and find the variation of the vertical stress with respect to the depth of the sand bed. I have conducted the same on the laboratory scale using a steel plate and placing pressure cells vertically below the plate as shown in the figure below. 
 
 My query is which stress should be selected from the list of stress to obtain the vertical stress that will be recorded by the pressure cells in the laboratory model?

Stefanos Papavasileiou · Answer

Dear Jerin, 
 Based on what I read you would use the cartesian stresses as then in 2D you can pick the &sigma;yy and for 3D you can pick the &sigma;zz. 
 The principal stress might also be interesting but the definition is the same as in mechanics you know from the university. 
 You can also read the details of each result available in our Reference manual.