Benchmark study of rock slope stability through Generalized Hoek-Brown criterion: case study of an open pit in Sudan

The non-linear Generalized Hoek-Brown (GHB) failure criterion for rock mass is widely accepted and has been applied in a large number of open pits slope designs. This paper proposes new equations for estimating the maximum confining stress from the (GHB) parameters and geometrical properties of the slope in the case where the strength ratio is critical (SR)_crit=(σ_ci/γH)_crit and the factor of safety (FOS)=1. This maximum confining stress can be used to calculate the global equivalent Mohr-Coulomb (MC) parameters. It was found that, compared to the calculation with the limit analysis method (LAM), the discrepancies do not exceed 5% and remain in the most cases less than 1%. Hence, the estimation of the (FOS) is much more improved, because the comparison of the literature’s results with the (LAM) leaded to a difference up to 21%. For any value of (FOS≠1), an iterative method has been proposed to evaluate (SR)_crit. The comparison between the results driven from this method and those of (LAM) showed a good agreement, which proves its accuracy. A case study has been conducted in an open pit located in Sudan to evaluate the discrepancy of the (FOS) provided by different methods using limit equilibrium method (LEM) with Rocscience Slide software and using the (LAM) given in the form of charts.