Finite element analysis incorporating the shear strength reduction method was applied to study the west slope stability of an open cut mine in Australia using Mohr–Coulomb and generalized Hoek–Brown criteria. The pit of the mine had multiphase excavations and reached 180 m in depth. The study investigated three slope configurations, namely, Stage 1 inter ramp slope 43°, Stage 2 inter ramp slope 49° and optimized Stage 2 slope 54°. When implementing the generalized Hoek–Brown failure criterion, the equivalent factor of safety was 1.96, 1.87 and 1.40 under dry slope for the three configurations, respectively. However, under partly saturated conditions, the optimised slope would have a factor of safety 1.16. Furthermore, the generalised Hoek–Brown criterion generated lower factors of safety than the Mohr–Coulomb failure criterion. The difference is related to an overestimation of the shear strength parameters by the linear Mohr–Coulomb criterion under low confining stresses compared with the non-linear Hoek–Brown.
The effect of three faults on the slope stability was studied for the Stage 1 open pit in an open cut mine in Australia. The faults were treated as joints using Barton's method, and the slope was under dry and partially saturated conditions. A finite element program in RocScience was used in the study, where the generalized Hoek-Brown criterion was employed for rock mass and the Mohr-coulomb criterion for the faults. It is found that the factor of safety of the slope decreased with the introduction of the fault structures. Furthermore, the fault structures created higher stress concentrations zones at the ends of the faults.