# Blocks unjoining when making a cut

**URL:** <https://forum.itascainternational.com/t/blocks-unjoining-when-making-a-cut/96>\
**Category:** 3DEC\
**Tags:** faq\
**Created:** [September 19, 2021, 7:21pm UTC](https://forum.itascainternational.com/t/blocks-unjoining-when-making-a-cut/96 "2021-09-19T19:21:12Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jhazzard](https://avatars.discourse-cdn.com/v4/letter/j/4af34b/32.png) [@jhazzard](https://forum.itascainternational.com/u/jhazzard)\
**Post date:** [September 19, 2021, 7:21pm UTC](https://forum.itascainternational.com/t/blocks-unjoining-when-making-a-cut/96/1 "2021-09-19T19:21:12Z")

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Sometimes you will find that blocks become unjoined when you make a cut in _3DEC_. This is because joined blocks must make a contiguous volume. See figure below. Imagine 3 joined blocks. You wish to create a true joint through the left block. The right block will be cut as well since you can’t have a joined volume with cuts going only part way through.

The way to deal with this is to make sure that you set the unwanted joints to be elastic with large stiffnesses so they have minimal effect on the results.

 ![unjoin](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/e9a7fb657c01dca4a26fe35c54a0d3c4126b71b2.png)

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**Author:** ![uncleyuan](https://avatars.discourse-cdn.com/v4/letter/u/f17d59/32.png) [@uncleyuan](https://forum.itascainternational.com/u/uncleyuan)\
**Post date:** [May 7, 2022, 2:52pm UTC](https://forum.itascainternational.com/t/blocks-unjoining-when-making-a-cut/96/2 "2022-05-07T14:52:16Z")

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hello, in the first case, a whole block are zoned, in the second case, joined blocks as one block are zoned, which has the same volume and same zones as block in the first block. which case will run faster? what are differences between these two cases?