When the Surface Type in the Surface Options dialog is Circular, the user can define:
Specific circular slip surfaces, and / or
A critical surface search to attempt to find the slip surface with the overall minimum safety factor for a given slope.
TIP: see the Slide Search Methods article for an overview of the different search methods in Slide and suggestions for using them effectively
Specific Circular Slip Surfaces
Specific circular slip surfaces can be added to a model with either of the Add Surface options in the Surfaces menu (two different options are available). Any number of specific circular slip surfaces can be added to a model.
Circular Surface Search Methods
There are THREE different Search Methods available in Slide for locating critical CIRCULAR slip surfaces:
Auto Refine Search
See the above topics for complete descriptions of these Search Methods.
For a given analysis, only ONE Search Method can be used, you cannot run different Search Methods at the same time.
However, specific circular surfaces AND a critical surface search can be defined and analyzed for the same model, this does not cause any problems.