# Unbalanced (out-of-balanced) force

**URL:** <https://forum.itascainternational.com/t/unbalanced-out-of-balanced-force/644>\
**Category:** 3DEC\
**Created:** [July 1, 2022, 3:45pm UTC](https://forum.itascainternational.com/t/unbalanced-out-of-balanced-force/644 "2022-07-01T15:45:54Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![VijayKiranKota](https://avatars.discourse-cdn.com/v4/letter/v/c4cdca/32.png) [@VijayKiranKota](https://forum.itascainternational.com/u/VijayKiranKota)\
**Post date:** [July 1, 2022, 3:45pm UTC](https://forum.itascainternational.com/t/unbalanced-out-of-balanced-force/644/1 "2022-07-01T15:45:54Z")

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This picture below is from one the examples : “Assessment of Fault Slip Potential from Sill Pillar Mining.”

It was mentioned that: The figure plots the unbalanced forces depicting how the model comes to equilibrium after each mining step.

May I know how to identify the lower limit of the Y-Axis Unbal forces? How to define the value?

In this particular example, the unbalanced forces were dropping from a value of 1.8_10^10 to 0.2_10^10.  
How was this lower limit (0.2\*10^10) fixed ?

I believe it is very important to identify this lower limit value to choose number of cycles/steps for the model to reach equilibrium?

 ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/2f15dc5e2483efda4977a281c7f419f32f4df56e.png)

Also, some times I get to see there is a spike in Unbal forces. Could it be due to joint slippage? If so then how to fix the number of steps required? And how to set the unbal ratio?

 ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/a672ff6ef3b5bd9abe28c3cb87a0d0187b352360.png)

Thanks,

V

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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:** [July 3, 2022, 11:59pm UTC](https://forum.itascainternational.com/t/unbalanced-out-of-balanced-force/644/2 "2022-07-03T23:59:09Z")

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The maximum unbalanced force is actually not that helpful. For small models you get small values, and for bigger models, you will get bigger values. A better measure is the unbalanced force _ratio_. You can take a history of this too. By default, the model is considered to be in equilibrium if the unbalanced force ratio is less than 1e-5.