Thanks for the replies Guys.
Unfortunately we don't have the resources to perform a 3D analysis - our report and analyses are caveated as such!
Just to clarify the seismic issue - that's an additional analysis, carried out as a separate analysis to the crane loading.
Long time lurker, first time poster, so any help is appreciated... I'm looking at an existing slope/gully which is essentially marginally stable, both on inspection and when analysing (FOS = 1.0 roughly). We've been asked to provide indication of a safe 'set-back distance' from the crest of the...