Uncertainty quantification of structural and geotechnical parameter by geostatistical simulations applied to a stability analysis case study with limited exploration data

Abstract

There are many uncertain factors impacting stability analyses of rock structures. Quantification of these factors significantly impact the engineering decision making process. Some of these factors are spatially distributed within the geological domain, and the quantification of the spatial uncertainty is beneficial for stability analysis of the structure. This paper proposes an integrated methodology for a stability analysis of rock structure by incorporating spatially varying factors. This research models two key factors: one categorical structural parameter (fault zones) and one continuous geotechnical parameter (rock quality designation (RQD)). Two geostatistical simulation algorithms i.e., sequential indicator simulation and sequential Gaussian simulation are applied to quantify the spatial uncertainty by generating multiple equiprobable simulation maps of fault zones and RQD values. A slope stability analysis is performed by modeling the spatially varying fault zones and RQD. The proposed method is validated using a synthetic data set. The results from the synthetic data show the stability value of the synthetic data closely match with stability value calculated from simulated data. Finally, the proposed method is applied to a slope stability analysis for an open pit mine design where limited exploration data is available. Geostatistically simulated RQD maps from the case study mine are analyzed to determine a safe slope angle of 44° for the open pit mining operation. The proposed method can be applied for quantifying other geotechnical risk and integrated within any stability analysis framework.