Geotechnical Analysis and Recommendations for Safe Slope Geometry in Nickel Laterite Open Mines in Tanggetada District

Abstract

Slope stability is a fundamental requirement in lateritic nickel open-pit mining, particularly in tropical regions where limonite and saprolite materials exhibit heterogeneous geotechnical properties and are sensitive to changes in moisture content and operational loading. This study aims to evaluate the physical and mechanical characteristics of lateritic materials and to formulate safe slope geometry recommendations for a lateritic nickel mining area in Tanggetada District, Southeast Sulawesi, Indonesia. The research integrates field investigation, geotechnical sampling, laboratory testing, diggability assessment, and slope stability analysis using the Limit Equilibrium Method under static and dynamic conditions. The analysis was conducted for single mine slopes, overall mine slopes, and overburden and ore dump slopes. The results indicate that limonite has higher cohesion, whereas saprolite shows higher water content and saturated unit weight, suggesting different slope responses for each material zone. Single mine slopes exhibit higher safety factors than overall slopes, while the overall ore dump represents the most critical configuration under dynamic loading. The recommended safe geometry consists of a 5 m single mine slope height at 55°, a 30 m overall mine slope height at 33°, a 5 m single dump slope height at 45°, and a 15 m overall dump slope height at 31°. These findings demonstrate that safe slope design in lateritic nickel open-pit mining requires the integration of material characterization, static and dynamic stability evaluation, geometry control, and continuous geotechnical monitoring to support safe and sustainable mining operations.