Hello,
I am currently working on a project that involves modeling interactions between PFC rigid blocks in the shape of axis aligned boxes with PFC balls (using PFC 6.00.30). The goal of the project is essentially to study the stability of a retaining wall composed of rigid blocks that is supporting a backfill soil (concept illustrated in the following figure).
However, when I am filling the space behind the retaining wall with enough balls such that the wall begins to topple, I start running into stability issues in my model where balls start penetrating into rigid blocks without having the contact being detected. This in turn causes the model to blow up once the ball’s centroid reaches the rigid block’s edge (see following gif).
Thinking this may have been caused by some contact detection/creation issues, I proceeded to change the following:
- Set tolerances for balls and rigid blocks to zero (helped reduce the number of times balls penetrated into rigid blocks)
- Changed the proximity distance (caused more instability)
- Reduced the timestep drastically (alleviated but did not eliminate the issue)
To further investigate potential contact issues between balls and rigid blocks, I created a very simple model consisting of two rigid blocks supported by a wall and had a ball resting right on top of the two rigid blocks (see below). Although the model was simple, it was unstable. Trying to run it without setting the tolerances to zero or without using a very small timestep gave an error message which read “The distance is getting larger - bad news”. After setting the tolerances to zero, I was able to get the model to run although it was still unstable.
The code used for the simple model with two rigid blocks and one ball is attached along with the code used for the retaining wall.
2RB_1Ball.txt (929 Bytes)
SIMPLE_PFC_CODE.txt (1.7 KB)
Has anyone run into similar issues with rigid block/ball contacts? Do you have have potential solutions in mind that could help?
Thank you!