This paper will discuss application of the Shear Strength Reduction (SSR) method, using finite element (FE) analysis, to determine the stability of slopes in blocky/jointed rock masses. It will demonstrate the method’s versatility and reliability through analysis of five simple examples. FE- SSR results are verified through comparison to the results of UDEC, a discrete element program. The paper provides arguments for incorporating SSR analysis into the standard solution toolkit of rock slope engineers.


The efficiency of the Shear Strength Reduction (SSR) method, based on finite element (FE) analysis, has been well demonstrated for slopes in soil or rock masses, which can be treated as continua (Hammah et al. 2004, 2005 a,b, 2006). (In the rest of the paper, this method of slope stability analysis will be labelled the FE-SSR method.) This paper intends to show that the FE-SSR method can be reliably extended to the analysis of slopes in blocky rock masses. The paper will analyze five slope examples. In all the cases the method determines critical failure mechanisms and factors of safety that compare very well with those obtaining from analysis with UDEC (Itasca 2004), a commercially available numerical analysis program that performs SSR analysis based on the Discrete Element Method (DEM). The FE-SSR approach offers several key benefits. It is very general and can be used with any geotechnical FE software. The widespread availability of such software today makes the approach readily accessible and constitutes the primary motivation for this paper. The paper will briefly describe unique aspects of the mechanical behaviour of blocky rock masses and why DEM tools have been traditionally applied to this class of geotechnical problems. It will then give an overview of the SSR method and show how the approach can be used with any FE program.

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