Slope Stability analysis based on rock mass rating (RMR) method at an open pit mine, east Java, Indonesia

Abstract A significant problem that often arises in open pit mining is slope instability. The hydrothermal processes allow mechanical and physical properties of the original rock mass to change, thus incurring challenges in open-pit mining operations. The purpose of this study is to analyze the slope stability of hydrothermally altered rocks in an open pit mine in Banyuwangi. Geotechnical investigations are crucial to obtain rock samples for laboratory testing. We employed the thin section method in petrographic analysis to determine the types of minerals present in the rocks, and the empirical Rock Mass Rating (RMR) classification to identify changes in hardness for each type of altered rock through the Point Load Index test. Based on the calculation results, the material properties required for the slope stability analysis were determined. This analysis was conducted using Rocscience software with the Limit Equilibrium Method to assess the Safety Factor, then the Total Displacement must be calculated using the Finite Element Method. This study highlights the importance of understanding alteration types and the characteristics of the rock mass. The stability of open pit slopes is significantly influenced by the type of alteration with low RMR values.