Self weight load of particle assembly

Hi everyone,

I am trying to create a model of a large particle assembly that is than later loaded by a few walls. It is important for me to create the assembly with a specific particle size distribution and a stress distribution that is created through particle density (K0 stress state or similar).

My approach is the following: I would use the brick methodology to first create a small representative particle assembly and use a typical homogeneous stress state that is close to the stress state at the centre of the large assembly (depending on density, porosity and contact properties of the particles). Then I would assemble the bricks.

In a following step I would like to create the desired stress state that is created using the “ball tractions layered” command as the documentation states this “computes the overburden based on integrating the density of balls above this current contact location” and that by “default the model is not assumed to be layered”.

What I dont understand is that this definition tells me that defining the density of the particles by default does not have an effect on the stress state. Is this correct? - i. e. from my understanding this example (Gravity Settlement in a Coupled PFC-FLAC3D model — PFC 7.0 documentation) tells a diffeent story in that respect.

Hello @Mussie,
That is not correct. The ball tractions commands is similar to initializing the stress state in zones. If you have an assembly of particles undergoing only gravitational loading you can assign a density and allow the particles to equilibrate under gravity like the example you mentioned. OR you can specify balls tractions with the layered option and equilibration should take less time since the stress state has already been prescribed.

Thank you very much @dblanksma! Now its clear to me! So I guess in order to be a bit quicker I will use the ball tractions command in my case :slight_smile:

Have a great day!

Cheers
Mussie