Calibration of a Three-dimensional Slope Stability Evaluation in Brazilian iron Open Pit Mine

Abstract

It has historically been frequent among geotechnical practitioners, that the stability analysis of the slopes of an open pit is performed using a two dimensional section representing the highest and steepest walls within a certain geological setting. However, the literature shows that to predict rupture events in an open pit, a three-dimensional analysis would better represent the actual conditions, as the spatial distribution of the lithology and the structural features play an important role when defining the stability of the slopes. This paper presents the case study of an open pit located in Brazil, which experienced instabilities between the years 2001 and 2019. An evaluation of the behavior of the open pit was performed by calibrating the strength parameters to represent the best documented rupture events. The three-dimensional model was made using the finite difference method. The results show that there is a good correlation between the results of the model and the reports of past instabilities. Finally, recommendations are presented for the inter-ramp angles for each lithology based on the calibrated stability analysis performed. This work seeks to contribute to the knowledge in evaluation techniques for the three-dimensional behavior of open pits.