What are some general guidelines for carrying out an SSR analysis in RS2?

The following are a few things to keep in mind when carrying out an SSR analysis in RS2:

  • Tutorial 8 illustrates how to set up a model for an SSR analysis
  • Use 6-noded triangles for an SSR analysis (the speed will be similar to 3-noded)
  • If material properties are set to zero, this will cause numerical issues, so always assign a small amount of cohesion and tensile strength (this is recommended for all analyses, in general)
  • The first thing to check when doing an SSR analysis is the Shear Strength Reduction Graph, and you should be looking for displacements taking off, diverging from the elastic part of the graph
  • Even for 6-noded triangles there can be mesh sensitivity, so always be mindful of this
  • It is recommended to use both Slide and RS2 to properly judge the factor of safety of a slope
  • In an SSR analysis, both the peak and residual strengths are reduced for a particular SRF value.  Residual values are used after failure of the material
  • The displacements at any stage of an SRF analysis are the displacements you would see if you reduced the strength of the in situ material by that SRF factor
  • The Stage Settings option in the Data menu allows you to set any reference stage, if desired, to view differential data between any two stages of a multi-stage model.  For an SSR analysis, if the reference stage is used, all the results are based on the difference between any SRF stage and the initial stage.  So, the model results of SRF=1 should equal the results of the initial stage.  The true displacements from an SSR analysis will be displayed if the reference stage is not used.
  • A pin at the edge of the model is preferable to a roller when doing SSR analyses, particularly if the boundary is close.  If rollers a used, the failure surface can propagate along the external boundary since it is in essence a frictionless, cohesionless surface.
  • Before doing an SSR analysis on a multi-stage model, one should always do the model without SSR first
  • It is not recommended to use the effective stress option with SSR