Transforming underground to surface mining operation – A geotechnical perspective from case study

Mining methods selection traditionally determined at the beginning of the feasibility study and non-changeable, along with the life of mine (LOM). The change in mining methods sometimes unavoidable when the criteria are met. One of the criteria is geotechnical aspects. This study was conducted through a case study in PT Cibaliung Sumberdaya. This study investigates geotechnical criteria that should be followed to transform an underground operation to surface operations. Geotechnical analysis conducted through numerical modeling using limit equilibrium and finite element methods. Parameter investigated in this study are Factor of Safety (FoS), Probability of Failure (PoF), stresses, and total displacement. The model and simulation were focusing on the area where there will be an intersection between underground openings and slope for surface mining. The allowed FoS and PoF for safety criteria are 1.05 and <10%, respectively, assuming moderate severity. The total displacement criteria for the safe working condition in the surface mining area is 1.80 m. In conclusion, the transformation of mining methods is feasible from a geotechnical perspective and should be followed with continuous monitoring.