Pengaplikasian Metode RMR dan FEM untuk Kestabilan Stope Tambang Bawah Tanah Serta Rekomendasi Penyanggaannya

Abstract

Underground mining operations require reliable ground support to maintain excavation stability, especially in production stopes within weak rock masses. At the study site, support design has traditionally relied on rockfall load estimation using the Rock Mass Rating (RMR) classification based on Bieniawski’s empirical guidelines. Although widely applied, this approach has limitations in representing rock mass behavior, resulting in uncertainty that may cause overdesign or underdesign. Therefore, this study evaluates production stope stability by integrating the empirical RMR method with numerical analysis using the Finite Element Method (FEM). The analysis utilizes secondary data, including RMR values, stope geometry, laboratory-derived rock mechanical properties (UCS, Young’s modulus, Poisson’s ratio, density, and tensile strength), and support system properties. The RMR value of 30 classifies the rock mass as class IV (poor rock), while empirical analysis using Unal’s formulation estimates a roof rockfall load of 65.625 tons. Based on Bieniawski’s recommendation, the empirical support consists of five 2.4 m split-set bolts with 1 m spacing and 0.1 m UCS28 shotcrete, providing 59.16 tons of capacity. FEM results show an initial FoS of 0.88–1.59, which decreases under seismic loading. An optimized support system combining rock bolts and an H-beam improves stability, increasing the FoS to 1.99–2.21 and complying the FoS ≥ 1.5 criterion in Kepmen ESDM No. 1827 K/30/MEM/2018. Overall, RMR-based design is suitable for preliminary assessment, while FEM optimization provides a more reliable ground support solution.