RS2 Features

Finite Element Slope Stability


One of the most exciting features of RS2 is finite element slope stability using the Shear Strength Reduction (SSR) method. This option is fully automated and can be used with either Mohr-Coulomb or Hoek-Brown strength parameters. With a single mouse click, you can run the SSR analysis and determine the critical strength reduction factor (safety factor) of a slope.

The SSR method has many advantages over the traditional limit equilibrium methods of slope stability. For example, SSR analysis does not require any assumptions about the shape or location of the failure surface. The SSR method will automatically determine the most critical failure mode and the corresponding safety factor.

For more information about SSR analysis with RS2 see the Shear Strength Reduction Overview topic in the RS2 Help system.

See each of the following aspects of the SSR analysis below:

Analysis Parameters
The SSR stability analysis in RS2 is fully automated; however the analysis parameters can be configured in the Project Settings dialog. You may specify the initial estimate of SRF, automatic or custom step size, tolerance and other parameters. In most cases the default parameters are sufficient, but advanced analysis settings can be customized if necessary.
Analysis Results
After the SSR analysis has been computed, the results for the critical Strength Reduction Factor (SRF) will automatically be displayed. Maximum shear strain contours are shown by default, as this tends to highlight the critical failure zone. The results for other values of SRF can be viewed by selecting the desired stage tab. Each stage tab represents the analysis results at a particular value of SRF.

You can plot SRF versus Maximum Total Displacement with the Graph Shear Strength Reduction option. This graph represents the essential results of the SSR analysis, and illustrates the iteration process used to determine the critical SRF. The critical SRF is the maximum value of SRF at which convergence is achieved for the finite element analysis. If the SRF is higher than the critical value the model is unstable (i.e. the finite element analysis does not converge within the specified number of iterations).
Search Area
By default the SSR analysis considers the stability of the entire model when the analysis is computed. This means that the critical failure zone may occur anywhere in the model. However, there are circumstances when you may wish to focus on the stability of a particular area of the model. This can be accomplished with the SSR Search Area option, which allows you to apply the SSR analysis to any region of the model.

For example, in a dam or embankment model, you may wish to analyze the stability of each side of the model independently.

The SSR Search Area option can be useful in other situations. For example, in a benched slope or open pit mine model, you may wish to analyze individual benches or regions of the slope. An SSR Search Area is easily defined by simply clicking and drawing a window over any portion of the model. Only the selected area of the model will be considered for the SSR analysis. Regions outside of the search area will be considered stable.
Joints
If your model includes joints, you can apply the SSR analysis to the joint strength by selecting the Apply SSR option in the Joint Properties dialog. If this checkbox is selected, then joint strength will be factored by the same amount as the surrounding material strength during the SSR analysis. By default, joint strength is not factored in a SSR analysis.
Import/Export Slide Files
Slide is a 2D limit equilibrium slope stability program available from Rocscience. If you wish to run an SSR analysis on a Slide model, slope models can be imported from Slideand computed in RS2 , allowing easy comparison of limit equilibrium and finite element results.

For more information see the Import Slide File topic in the RS2 Help system.

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