Geomechanical reserves for optimizing open-pit slope design during the final mine development stage

This study explores the potential for additional geomechanical optimization of the slope design for deep openpit mines during the final operational stage. Feasibility of applying a reduced safety factor of 1.2 for slope sections with the Koashva deposit as a case study. The research provides a detailed analysis of the risks associated with rock mass fracturing, presence of carbonate rock, oxidation processes, and groundwater inflow. An assessment is conducted regarding the inward shift of the top edge of the slope and the consequent reduction in the overburden volume through implementation of a dedicated final development phase. Slope stability calculations were performed using the limit equilibrium method with circular slip surfaces for critical profiles of the hanging wall, where the initial safety factor equals 1.31. Results indicate that shifting the top edge into the ore body by 28.4 to 31.5 meters aligns the slope coordinates at the minus 188 meter level with the design configuration while significantly increasing recoverable reserves at the lower levels. For the adjusted contour during the final development stage, the calculated safety factor ranges from 1.24 to 1.26, fully complying with the regulatory requirements. An integrated approach that combines refined geomechanical modeling, optimized blasting operations, and a hierarchical monitoring system, slope optimization in the analyzed sector is estimated at 4.5 billion Rubles, which is equivalent to eliminating 22.9 million cubic meters of conditional overburden.