Triaxial Testing of Soil Element

[mline41]

Dear STKO Team,

I am trying to do a triaxial test of a soil element.

Please see images, powerpoint and model to understand better.

I have produced a cube element, with dimensions of 0.1m, in the model attached. on 3 adjacent sides, there is a stress acting perpendicular to the face, which are an axial stress acting down on the top face, and radial stress acting on 2 of the side faces. The axial stress = radial stress = 20kPa. Given that the area of the face is 0.01 meters squared, the face force has a value of 200N. Boundary conditions are applied on the 3 remaining adjacent sides of the cube, by which they are constrained in the direction perpendicular to the face.

An additional downward displacement is applied to the top face of 0.02m (20% strain). This displacement should be applied through a linearly increasing time step, after the initial confining pressures were applied.

The soil is to be modelled using the Drucker-Prager yield criteria.

A) Please would you be able to check that my model attached reflects the above conditions.

B) I would like to produce 3 graphs that explain the soil behaviour.

1. Deviatoric Stress vs Isotopic Stress

2. Deviatoric Stress vs Deviatoric Strain

3. Volumetric Strain vs Deviatoric Stress

- Please could you advise on how I could produce these graphs.

Please See attached Powerpoint and Model.

Many thanks in advance

[mline41]

PLEASE NOTE: Throughout the test, the change in axial stress is non 0. However, the change in radial stress is 0. That is why in my model, I have applied the initial stresses through a constant time step. Then I have applied the displacement through a linear time step.

[mline41]

UPDATE: My previous model was meshed incorrectly. As this is a test on an element, there should only be one element in the mesh. I have attached my updated model. How can I extract data to plot the graphs?

1. Deviatoric Stress vs Isotopic Stress

2. Deviatoric Stress vs Deviatoric Strain

3. Volumetric Strain vs Deviatoric Stress

As shown in previous message. I believe I have to extract data from the gauss points some how.

Thanks in advance.

[mline41]

Hi,

Also please note that the previously given formula for isotropic stress was incorrect.

It should be:

[STKO Team]

Create a gauss plot,
select the gauss point of interest
use the command Extract chart data and follow the instructions on the Wizard