Analysis of the Stabilty of the Mining Site Slope on Bunyu Island, Bulungan Regency, North Kalimantan Province

Abstract

Slope collapse can occur due to the reduction of shear strength and the addition of shear stress to the soil layer that forms the slope. This study aims to analyze the slope stability in the mining area of PT Garda Tujuh Buana on Bunyu Island, North Kalimantan. The research locations are in the South Block and West Block with open pit mining methods, which have a high risk of slope landslides. An evaluation was carried out on the existing slope geometry using the Morgenstern-Price method  approach with the help of the Rocscience Slide 6.0 software. The geotechnical parameters analyzed include the physical and mechanical properties of the materials that make up the slope such as cohesion, inner shear angle, and content weight, as well as external factors such as rainfall and groundwater level.

The results of the analysis show that some slopes, especially in Sections 3, 4, and 5 in both blocks, have  a Probability of Failure (PoF) value  above the threshold set by the Ministry of Energy and Mineral Resources No. 1827 K/30/MEM/2018, even though the Factor of Safety (FS)  value still meets the minimum criteria. Through the trial and error method, new geometric recommendations were made with changes in the angle of slope, level height, and removal of soil material that has low shear strength. The results show a significant increase  in the value of FS and a significant decrease  in PoF until it reaches national stability standards. This study contributes to efforts to mitigate landslide risks and improve the safety and efficiency of mine operations.