Unbalanced (out-of-balanced) force

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 1.810^10 to 0.210^10.
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?

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?



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.

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