If you don't find anything anywhere else written, for whatever the works subject to sliding and overturning on the ground, the usual safety factors are 2 for overturning and 1.5 for sliding.

If the 2 factor can be reduced to 1.5 or even less it is a matter of engineering judgement. One might think such is the case where the values of the variables used have been finely investigated and so defined.

I wouldn't consider 1.0 a safety factor??????????

Certainly it is not, but you know, what for some is just what needed for others is an exaggeration. And really I endorse the practice of the 2 and 1.5 safety factors for overturning and slippage as a minimum. If the factor against slippage goes under 1.5 for the reasonable variations of size within the structural type, maybe is the time to change the structure to one that has more lateral support against such splippage.

I believe the O.M. is .6 X the R.M. or FS 5/3 or 1.67 and FS for slidng is 1.5