Strength Reduction Technique with Finite Element Method for Slopes Without Stabilisation Measures

The NAFEMS Geotechnical Working Group are currently developing guidance material on how to analyse slope stability problems.
The working group will be publishing a collection of papers on this topic that have been scoped and peer reviewed by the working group.
This is the first of these papers, and the full collection will be available shortly.

Limit equilibrium analyses e.g. by Janbu, Bishop, Morgenstern & Price and Spencer, are currently the preferred method in practical geotechnical engineering to calculate factors of safety, particularly in slope stability analysis. However, alternative methods such as the strength reduction technique in combination with the displacement based finite element method (e.g. Brinkgreve & Bakker, Griffiths & Lane, Dawson et al., have been proposed as an alternative approach with significant advantages over limit equilibrium methods, albeit with somewhat increased computational costs. It has been shown that limit equilibrium and finite element methods can produce similar factors of safety for slope stability analysis (e.g. Cheng et al.,. However, as is shown in this paper, significant differences may occur under certain circumstances. Consequently, the question has to be answered; Which of the methods leads to more realistic results? An attempt to demonstrate that strength reduction methods produce reliable results has been made by Tschuchnigg et al. by comparison with finite element limit analysis, which provides rigorous upper and lower bounds on the factor of safety (e.g. Sloan, Sloan, Sloan & Kleeman], Lyamin & Sloan, Lyamin & Sloan, Krabbenhoft et al.).