Improved probabilistic kinematic analysis procedure based on finite size discontinuities and its application to a rock slope at open pit mine in U.S.

An improved probabilistic kinematic analysis procedure is suggested incorporating the six steps listed in the paper. The variability of the shear strength and discontinuity orientation is taken into account in the probabilistic kinematic analysis. The correlation that exists between the dip angle and dip direction is incorporated in modeling discontinuity orientation by treating it as a bivariate random variable. A part of an open pit mine in the United States was investigated by performing deterministic and probabilistic kinematic analyses. Field and laboratory investigations were conducted to obtain the needed geological and geotechnical data for the analyses. Important differences were obtained between the probabilistic and deterministic kinematic analyses results mainly because of the variability of the discontinuity orientations. The results confirmed that the designed value of the maximum safe slope angle (MSSA) for a particular region in the open pit mine calculated according to the deterministic kinematic analysis can be on the unsafe side. The probabilistic kinematic analysis showed superiority over the deterministic kinematic analysis in providing additional important information regarding designing rock slopes. Based on the previous analyses results available for the same site using block theory, it was found that a 5% instability cumulative probability based on block theory seems to provide a similar level of risk compared with that of 15% based on kinematic analysis results. The calculated MSSA values are in good agreement with the existing quite stable bench face angles reported by the mining company.