Numerical analyses of the effects of rock Mass property variability on open stope stability

The rock mass is intrinsically variable in its physical and mechanical properties which makes it complex. This complexity is evident from the spatial random distribution of the properties from any site characterization program. The precise values for these properties are never known in most cases hence most geotechnical mine designs are based on fixed or discrete values of rock mass properties for stability analysis. This traditional deterministic approach neither reflects the inherent variability nor the uncertainty in the rock mass properties. Therefore, it is desirable to utilize a probabilistic approach which provides a range of possible results based on the variability in the rock mass properties. Understanding the effect of this random distribution and variability of the properties on stope stability is essential for more realistic mine design. In this study, a series of numerical analyses using the explicit finite difference element code FLAC, have been conducted to study the effect of the random distribution and variability of rock mass properties on the stope stability. The rock mass in the FLAC model is represented by different material properties randomly distributed to each zone. In order to compare the results, fixed average values of the material properties were also used for the FLAC model in another simulation. The results clearly indicate that rock mass property variability does affect the stope stability and that a deterministic approach to stope stability analysis could lead to conservative results.