Sensitivity Analysis Overview

In addition to the Probabilistic Analysis capability of Slide, you may also perform a Sensitivity Analysis.

In a Sensitivity Analysis, individual input parameters are varied between user defined minimum and maximum values. This results in a plot of safety factor versus the parameter value, and allows the user to determine which input parameters have the greatest effect on safety factor, and which parameters do not have much effect on the safety factor.

A Sensitivity Analysis should not be confused with a Probabilistic Analysis. Although the methods of selecting and defining variables are the same, the purpose and results of a Sensitivity Analysis are different from a Probabilistic Analysis. In a Sensitivity Analysis, only a SINGLE VARIABLE is varied at a time, while all other variables are held constant, at their mean value.

For more information about Sensitivity Analysis with Slide, see the Sensitivity Analysis topic in the Project Settings section of this Help system.

To carry out a Sensitivity Analysis:

  1. Select the Sensitivity Analysis checkbox, on the Statistics page in the Project Settings dialog.

  2. The method of selecting and defining variables to be used in a Sensitivity analysis, is the same as described for a Probabilistic Analysis, using the options in the Statistics menu. Just remember that only the Minimum and Maximum values of the selected variables are applicable – Statistical Distribution and Standard Deviation are not applicable for a Sensitivity Analysis.

  3. NOTE: in the input data dialogs, the minimum and maximum values are specified as RELATIVE distances from the mean value, because this simplifies the data input. During the analysis, these are converted to the actual minimum and maximum values, as follows:

MINIMUM = MEAN – Relative MINIMUM

MAXIMUM = MEAN + Relative MAXIMUM

  1. When Compute is selected the Sensitivity Analysis will automatically be carried out after the regular (DETERMINISTIC) analysis is completed. Each selected variable will be varied between its Minimum and Maximum values, in 50 equal increments, and the safety factor for the Global Minimum slip surface will be calculated for each value.

  2. The Sensitivity Analysis results may then be viewed in the Slide Interpret program. The results are simply a graph of safety factor (for the Global Minimum slip surface) versus the parameter value. If multiple parameters have been selected for the Sensitivity Analysis, all curves are displayed on the same plot, by plotting all parameters on a normalized scale of 0 to 100 percent, where 0 represents the Minimum value of each parameter, and 100 represents the Maximum value of each parameter.