KAJIAN GEOTEKNIK UNTUK PERENCANAAN GEOMETRI LERENG PIT TAMBANG NIKEL MENGGUNAKAN METODE BISHOP SIMPLIFIED PADA PT. RIOTA JAYA LESTARI

Abstract

The mining process for laterite nickel ore, especially for open pit mines, needs to be carried out on the slopes of geotechnical studies in order to create a safe and conducive mining environment, in accordance (Decree of the Minister of Energy and Mineral Resources of the Republic of Indonesia No. 1827 K/30/MEM/2018). This study aims to provide recommendations for safe mine slope geometry based on the physical and mechanical properties of the soil making up the slopes in the mining plan for Block 2 pit 6A at PT. Riota Jaya Lestari, Totallang Village, Lasusua District, North Kolaka Regency, Southeast Sulawesi Province. The method used in determining slope stability in this study is the Bishop Simplified method. The results showed a simulation of slope stability on the profile of laterite nickel deposits under conditions of distributed additional load by the excavator of 74 kN/m2, for a single slope of 6 meters in the Overburden layer with a slope angle of 40^o obtained a FK of 1.6 and a PL of 0%, while for an angle of 80^o the FK is 0.9 and the PL is 100%. In the Limonite layer, for the 40^o angle, the FK is 1.5 and the PL is 0%, while for the 80^o angle, the FK is 0.8 and the PL is 100%. Furthermore, the Saprolite layer for an angle of 40^o obtained a FK of 1.4 and a PL of 0%, while for an angle of 80^o the FK was 0.8 and a PL of 100%. Then for the Overall slope with the three types of coating as high as 18 meters for a slope angle of 35^o with a basic slope geometry of 6 meters and an angle of 40^o, the FK is 1.2 and the PL is 0%. Meanwhile, for a slope angle of 69^o with a base slope geometry of 6 meters and an angle of 80^o, the FK is 0.6 and the PL is 100%. Based on the results of the study, it can be concluded for the overall slope to use the basic slope angle with a height of 6 meters and an angle of 40^o, because it is considered safer to be used to design or design mine slopes based on the physical and mechanical properties of the soil in Block 2 pit 6A.