Refky Adi Nata, Gaofeng Ren, Yongxiang Ge, Congrui Zhang, Luwei Zhang, Heriyanto Panggabean, Verra Syahmer
Slope instability in open-pit coal mines threatens safety and infrastructure. Displacement phenomena (cracks, deflection, heaving) signal potential failure. While counterweight backfilling stabilizes slopes, site-specific protocols for heterogeneous settings, such as Indonesia’s Barito Basin (Warukin Formation), lack standardization. This study addresses this gap at PT. Bhumi Rantau Energi’s Mahoni Pit by integrating high-resolution displacement monitoring (Leica Nova TM50), geotechnical analysis (RQD, RMR), and numerical modeling (SLIDE 7.0, RS2 v11). The objectives were to characterize the displacement mechanisms, quantify the counterweight effectiveness, and optimize the geometry. The results show “warning”-level velocities (>10 mm.h−1) across points, with peak displacement (907 mm.day−1 at IPD_MHN_26) driven by pore pressure in weak fill/mud layers (c′: 2–20 kPa; thickness: 71–100 m). Counterweights significantly increased the Factor of Safety (FoS) from critical levels (e.g., 0.960, PF = 74.4%) to stable values (e.g., 1.160, PF = 1.8%), representing 20–35% improvements. RS2 identified fill material as the primary displacement zone (max: 2.10 m). Optimized designs featured phased backfilling (200 k–10 M BCM) with a 50 m width and 11° inclination. Tailored counterweight deployment effectively mitigated the instability in slopes underlain by weak strata. The integrated approach provides a validated framework for optimizing designs in similar sedimentary basins, enhancing safety and reducing costs. © 2025 by the authors.
Mining Engineering Department, School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan, 430070, China; Mining Engineering Department, Faculty of Engineering, Universitas Negeri Padang, Padang, 25131, Indonesia; Key Laboratory of Green Utilization of Critical Non-Metallic Mineral Resources, Ministry of Education, Wuhan University of Technology, Wuhan, 430070, China; PT. Bhumi Rantau Energi, Kalimantan, 71112, Indonesia; Agro Industrial Engineering Department, Politeknik ATI Padang, Padang, 25171, Indonesia
