# Contact disappears

**URL:** <https://forum.itascainternational.com/t/contact-disappears/1039>\
**Category:** PFC\
**Created:** [May 23, 2023, 1:09pm UTC](https://forum.itascainternational.com/t/contact-disappears/1039 "2023-05-23T13:09:33Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Prerna](https://avatars.discourse-cdn.com/v4/letter/p/eada6e/32.png) [@Prerna](https://forum.itascainternational.com/u/Prerna)\
**Post date:** [May 23, 2023, 1:09pm UTC](https://forum.itascainternational.com/t/contact-disappears/1039/1 "2023-05-23T13:09:33Z")

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Hello.  
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.

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**Author:** ![dblanksma](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@dblanksma](https://forum.itascainternational.com/u/dblanksma)\
**Post date:** [May 23, 2023, 8:27pm UTC](https://forum.itascainternational.com/t/contact-disappears/1039/2 "2023-05-23T20:27:56Z")

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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 [PFCsupport@itascacg.com](mailto:PFCsupport@itascacg.com).

– Derrick