triaxial-compression-of-sand.md

Triaxial Compression of Sand Using SimpleSand

In this example, we demonstrate the usage of SimpleSand model by conducting a triaxial compression simulation.

The model scripts can be downloaded.

The Model

A unit cube defined with C3D8 element is used to represent the specimen.

node 1 .5 -.5 0
node 2 .5 .5 0
node 3 -.5 .5 0
node 4 -.5 -.5 0
node 5 .5 -.5 1
node 6 .5 .5 1
node 7 -.5 .5 1
node 8 -.5 -.5 1

element C3D8 1 1 2 3 4 5 6 7 8 1 G

For the material properties, the following values are used.

material SimpleSand 1 9E4 .2 .01 -.7 5. 1.25 1.1 3.5 1.6 -130. .02 2.

Please refer to the corresponding page for explanations.

Loading

The confinement is applied to achieve a confinement stress of $$\sigma=3000~\mathrm{kPa}$$.

In this case, a displacement of $$-0.01$$ would do the job.

displacement 1 0 -0.02 1 1 2 5 6
displacement 2 0 -0.02 2 2 3 6 7

The vertical displacement is applied in the same way.

Monotonic

amplitude Tabular 1 monotonic

displacement 3 1 -0.02 3 5 6 7 8

Cyclic

Cyclic displacement load can be applied. It varies cyclicly after the target confinement is achieved.

amplitude Tabular 1 cyclic

displacement 3 1 -0.02 3 5 6 7 8

The load level can be plotted as follows.

Result

The $$p$$-$$q$$ response is shown as follows. As a linear relationship is assumed for elastic part, linear line segments are expected within the yield surface.

The SimpleSand model is a very simple model for sand to showcase the concept of bounding surface.

For more advanced response, other models shall be used.