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.

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1 2 3 4 5 6 7 8 9 10	`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.

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1	`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.

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1 2	`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

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1 2 3	`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.

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1 2 3	`amplitude Tabular 1 cyclic displacement 3 1 -0.02 3 5 6 7 8`

The load level can be plotted as follows.

load level

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.

monotonic result

cyclic result

For more advanced response, other models shall be used.