GEOTECHNICAL STABILITY AND ENVIRONMENTAL RISK MITIGATION OF THE MBAH SOERO UNDERGROUND MINE

Abstract

Underground excavations in historical mining areas require comprehensive geotechnical evaluation to ensure long-term stability and public safety. The Mbah Soero underground coal mine in Sawahlunto City, Indonesia, is a former mining site that has been repurposed as a heritage tourism and educational facility, where tunnel stability and environmental risk mitigation are critical concerns. This study aims to evaluate the geotechnical stability of the underground openings and to develop mitigation strategies based on empirical classification, numerical modeling, and geophysical investigation. Face mapping was conducted at four tunnel faces to characterize rock mass conditions, supported by laboratory testing of physical and mechanical properties, including point load index tests converted to uniaxial compressive strength values. Rock mass quality was assessed using the Rock Mass Rating (RMR) system, with Q-System values estimated through empirical conversion. Numerical stability analysis was performed using finite element modeling in RS2 Rocsience software to determine safety factors and identify critical zones. Electrical resistivity surveys were carried out along three profiles to support subsurface lithological interpretation related to coal-bearing formations. The results indicate that the tunnel system is generally stable, with safety factor values exceeding critical thresholds, although localized zones require monitoring and limited reinforcement. The integrated approach provides a practical framework for stability assessment and risk mitigation in underground heritage mines.