Stability Analysis of Pit B Slope Using RMR (Rock Mass Rating) And GSI (Geological Strength Index) Methods At PT. Halo Tambang Berjaya, Kalianda District, South Lampung Regency

Abstract

The research area is located at PT Halo Tambang Berjaya, Kalianda District, South Lampung Regency, with the main objective of analyzing slope stability in the open pit mining area using the rock mass rating (RMR) and geological strength index (GSI) methods. The RMR method is used to assess the strength of the rock mass through geotechnical parameters such as intact rock strength, rock quality designation (RQD), spacing of discontinuities, condition of discontinuities, and groundwater conditions. GSI is used to obtain a more detailed picture of the rock mass quality through the structure rating (SR) and surface condition rating (SCR) parameters. The analysis was carried out on one slope in the Pit B area with a 7 meter scanline. The RMR value obtained was 75 (good rock class), and the GSI value was 48 (good rock class). Based on these results, it can be concluded that the slope in the research area is classified as good and stable, so it is relatively safe to support mining activities. However, it is necessary to carry out regular monitoring of geotechnical conditions, especially in slope sectors with close discontinuities, to prevent potential landslides in the future.