# A strange bug during coupled pore pressure dissipation

**URL:** <https://forum.itascainternational.com/t/a-strange-bug-during-coupled-pore-pressure-dissipation/588>\
**Category:** FLAC3D\
**Created:** [May 31, 2022, 1:25pm UTC](https://forum.itascainternational.com/t/a-strange-bug-during-coupled-pore-pressure-dissipation/588 "2022-05-31T13:25:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![FLAC3D\_GEO](https://avatars.discourse-cdn.com/v4/letter/f/f1d935/32.png) [@FLAC3D\_GEO](https://forum.itascainternational.com/u/FLAC3D_GEO)\
**Post date:** [May 31, 2022, 1:25pm UTC](https://forum.itascainternational.com/t/a-strange-bug-during-coupled-pore-pressure-dissipation/588/1 "2022-05-31T13:25:17Z")

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Hi Itascan, Please see below two screen-shots, the top one with “time-total = 86400” which is working properly, while for the bottom one with “time-total = 8640”, only one mechamical substep will be executed for every flow step, regardless of mechnical convergence. Looks like when the “time-total” is less than a certain value, FLAC3D is not working properly. I believe this is bug.

 ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/7ec6c97b41b9d236c4cf405cf5d5cecc1367152c.png)

 ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/35be4b325e199d3a486da608941d6f22d93772f4.png)

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**Author:** ![cheng](https://avatars.discourse-cdn.com/v4/letter/c/ecccb3/32.png) [@cheng](https://forum.itascainternational.com/u/cheng)\
**Post date:** [May 31, 2022, 4:11pm UTC](https://forum.itascainternational.com/t/a-strange-bug-during-coupled-pore-pressure-dissipation/588/2 "2022-05-31T16:11:51Z")

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I would suggest you send the datafile to Itasca for an investigation.