Contact disappears

I have been trying to solve a retaining wall soil system in PFC3D. For soil particles: rolling resistance model, for wall particles: the parallel bond model, for wall soil interface: rolling resistance model. But something is going wrong. With time the contacts between becomes zero and balls remains there. I do not understand what I am doing wrong. Please suggest what can be the issue. It would be of great help.
Thank you.

Hello Prerna,

Without looking at your data files it’s difficult to say what is the problem. In this case, I would suggest sending your question along with all necessary data files to

– Derrick