Exclude some zones in Strength reduction calculation

In some cases, the zones in slope is out of our interest during strength reduction calculation, such as bedrocks. So if it possible to pick them out from our SR calculation? (but not assign a null cm for these zones!) it definetely will save the calculation time and without change the result.
Acturally, this method is widely used by other FEM software, such as Phase2.

I don’t think we can specify a range of zones in FOS command. However, you can customize the FOS scheme with a fishcall which is straightforward.
For you case, why don’t you simply assign the elastic model to the bedrocks?

Yes, we can apply the fish or python to manually exclude the bedrock, but this is not so straightforward.
The fos calculation is not support the elastic cm in the model.