This rock slope example is also run using FLAC/Slope, see Section 1.4.5 in the FLAC/Slope User’s
Guide. The factor of safety calculated in the FLAC/Slope simulation is 1.38, and the failure pattern is slightly different. For example, compare Figure 10.5 to Figure 1.96 in the FLAC/Slope User’s Guide. This difference is related to the effect of the loading path on the development of tensile failure in the model. In FLAC/Slope, the SOLVE fos solution is invoked from an initial stress state of zero in the model. In this example, the model is brought to an equilibrium stress state, with only a minor amount of tensile failure, before the SOLVE fos solution is performed. The approach in FLAC/Slope produces slightly more tensile failure in the model. Note that if the tensile strength is set to a high value (e.g., 0.14 MPa), then no tensile failure occurs, and the calculated factor of safety is the same for both simulations: 1.41.