Retaining Wall Design - Formula for Sliding FS

[CWEngineer]

I have seen different formulas to determine factor of safety, and wanted to see which one is more appropriate or the current standard of practice.

For Example:
1. Coduto Foundation Design has, factor of safety is the ratio of the horizontal resisting forces to the horizontal driving forces.
2. Have seen the Sliding Force = Net Horizontal Forces in the wall (i.e, Horizontal Driving Forces minus Horizontal Resisting Forces). Resisting Force = (SUM V)*tan(phi_drained). Then FS = Resisting Force/Sliding Force.
3. Factor of safety for sliding = [(gravity force - uplift) x v + passive resisting force)]/sliding force, where sliding force is the driving forces.
4. Old shear-friction definition: FS = (R + Pp)/sumH, where R is the horizontal sliding resistance, Pp is the passive resistance and sumH is the net applied horizontal driving force.

Appreciate your input and guidance.

 

[bridgebuster]

In bridge, using the AASHTO Standard Specifications we always used:

FS = Vertical forces(soil except what's over the toe plus structure weight)times a friction factor divided by Driving Force (earth pressure plus surcharge)>1.5 OK