Model in WinSTABL before analysis was performed.
WinSTABL slope stability analysis results. Safety factors, also known as factors of safety (FS), are highlight in yellow.
Figure 1 below shows the model after all parameters – such as the profile, stratigraphy, and groundwater table – were input into WinSTABL. This was before the slope stability analysis was performed.
Figure 2 below is displaying thel results after WinSTABL was used to perform the slope stability analysis. The results displayed are the ten most severe safety factors, also known as factors of safety (FS), along with their respective slip surfaces. In general, a FS of greater than 1.0 represents a stable slope, while a FS of less than 1.0 represents an unstable slope. Although this is the general definition, it is not exactly what is used in practice.
According to sources, a FS of "1.1 or 1.2 may be considered reasonable for a natural slope, the failure of which is considered unlikely to have adverse consequences...a high factor of safety (say 1.5 or 2.0) may be required for an engineered slope" [6].
The FS of the slope at Alpha Iota may be acceptable for a natural landscape, but this is not the case. The Alpha Iota site contains a building with historic and sentimental value, for which a slope failure could be disastrous. Therefore, the FS determined through this analysis prove concerning. With current technologies and prediction strategies, it is impossible to tell exactly when a slope will fail. Regardless, the slope at Alpha Iota, particularly on the east side of the lakefront, is in pending threat of a detrimental slope failure.