Bultfontein Road - Kimberley Slope Stability Evaluation

content Input Data for Kimberley Pit Slope Analysis Results of Slope Stability Analysis Break-Back Process Analysis Conclusions

INPUT DATA FOR KIMBERLEY SLOPE ANALYSIS

Kimberley Pit East Slope

Boreholes and Sections

Idealization of Slope

Rock Mass Properties

Results of Slope Stability Analysis

Deep and Shallow Seated Failures

Summary Results Limit Equilibrium Stability Analysis

Break-Back Process Analysis

Historic Rate of Break-Back

Rate of Break-Back and Slope Angle

Risk Zones as Function of Slope Angle

Interpretation of Risk Zones

Conclusions

Conclusions The results of the geotechnical analysis indicate that: The occurrence of shallow failures in the more disturbed material close to the slope face is more likely due to the natural degradation of rock mass conditions with time. Time is a factor that has an effect on the stability conditions of the slope, but it is also a factor difficult to account for in engineering models at the present time. Current risk to the Bultfontein Road has been defined in a qualitative manner in terms of overall slope angle as low risk (<30º), moderate risk (30º to 33º), high risk (33º to 36º) and very high risk (>36º). These angles define corresponding zones of risk around the pit with levels of risk increasing towards the slope crest. The Bultfontein Road is currently located within the low risk zone. Slope break-back and surface deterioration will continue, and periodic shallow failures will be experienced from time to time, though it is difficult to predict the rate of occurrence of these events. Continuous slope inspections and monitoring are the available strategies to anticipate the occurrence of failure events. The likelihood of a deep seated failure (in the geology underpinning the pit) affecting the Bultfontein Road is very small.