If the Probabilistic Analysis Type = Overall Slope (as specified in the Project Settings dialog in the Slide Model program), then the slip surface search is repeated N times, where N = Number of Samples. Each search is performed by loading a new set of random samples, and then running the analysis.
For this type of Probabilistic Analysis, each search, using different random input data, can locate a different Global Minimum slip surface. In general, when the Probabilistic Analysis Type = Overall Slope, multiple Global Minimum surfaces will be located. (Between 10 and 50 different surfaces, is typical).
The Show GM Surfaces option in the Statistics menu, allows you to toggle the display of all of the Global Minimum slip surfaces located by the Overall Slope option. By default, when you open a file in Interpret, the Show GM Surfaces option will be ON (if the Probabilistic Analysis Type = Overall Slope).
Number of Analyses Represented by Each GM Surface
It is important to realize that EACH SLIP SURFACE which is displayed by the Show GM Surfaces option, can represent MORE THAN ONE iteration of the probabilistic analysis.
The number of analyses represented by each surface, is available to the user as a tool tip, using the mouse. When the Global Minimum slip surfaces are displayed, hover the mouse over one of the surfaces. A popup tool tip will indicate:
The number of analyses, relative to the total number of samples (for example: 25% of surfaces, 250 / 1000)
The range of different safety factors represented by the slip surface (for example: 0.9 to 1.25)
This is illustrated in the following figure. NOTE: in most cases, it will be helpful (or necessary), to Zoom In to the slip surfaces, so that you can accurately hover the mouse over the desired surface(s), to view the tooltip information.
Tooltip information display with Show GM Surfaces option.
Pick GM Surfaces
The Probabilistic Analysis results associated with any individual surface, or any combination of surfaces displayed by the Show GM Surfaces option, can be viewed by first selecting surfaces with the Pick GM Surfaces option, and then generating the desired plot. See the Pick GM Surfaces topic for details.