Analisis Stabilitas Lereng Disposal Pada Desain In Pit Dump E, Daerah Lawang Kidul, Kabupaten Muara Enim, Sumatra Selatan

Abstract

Metode penambangan terbuka (open pit mining) batubara membutuhkan pendekatan efektif dalam manajemen material lapisan penutup (overburden), di mana penimbunan di bekas pit (in pit dump) sering diterapkan. Namun, genangan air dan akumulasi lumpur di dasar pit merupakan variabel kritis yang meningkatkan potensi ketidakstabilan lereng dan risiko longsor. Penelitian ini bertujuan menganalisis kuantitatif kestabilan lereng desain disposal in pit dump di PT Pamapersada Nusantara, Muara Enim, Sumatera Selatan, fokus pada dampak kondisi lumpur maksimal. Analisis stabilitas dilakukan menggunakan pendekatan Limit Equilibrium Method (LEM), metode Morgenstern-Price, pada enam penampang. Empat penampang (A-D) untuk desain awal dan dua penampang (E-F) untuk kondisi lumpur maksimal. Hasil perhitungan faktor keamanan (FK) menunjukkan kontras signifikan. Berdasarkan standar Keputusan Menteri ESDM No. 1827 K/30/MEM Tahun 2018 (FK>1,3), hanya penampang C-C’ (FK = 2,304) dan D–D’ (FK = 2,271) yang tergolong aman. Sebaliknya, empat penampang tersisa (A–A’, B–B’, E–E’, dan F–F’) memiliki nilai FK < 1,3. Secara spesifik, penampang E–E’ dan F–F’ menunjukkan FK yang sangat rendah, menegaskan bahwa kehadiran lumpur adalah faktor dominan penyebab ketidakstabilan. Kondisi ini mengindikasikan bahwa sebagian besar lereng timbunan berisiko tinggi mengalami longsor dan dikategorikan tidak aman. Oleh karena itu, hasil analisis ini memberikan gambaran yang dapat dijadikan pertimbangan dalam perencanaan desain ulang geometri lebih lanjut.Open pit mining for coal requires an effective approach to overburden management, frequently employing in pit dumping (spoil disposal in excavated pits). However, water ponding and mud accumulation at the pit floor are  critical variables that increase the potential for slope instability and the risk of landslides. This research aims to quantitatively analyze the stability of the proposed in pit dump design slopes at PT Pamapersada Nusantara, Muara Enim, South Sumatra, focusing on the impact of maximum mud conditions. The stability analysis was conducted using the Limit Equilibrium Method (LEM), specifically the Morgenstern-Price method, applied across six cross-sections. Four sections (A–D) represent the initial design, and two sections (E–F) represent the maximum mud conditions. The calculated Factor of Safety (FS) revealed significant contrasts. Based on the standard set by the Minister of Energy and Mineral Resources Decree No. 1827 K/30/MEM Year 2018 (FS > 1.3), only sections C–C’ (FS = 2.304) and D–D’ (F = 2.271) are classified as safe. Conversely, the four remaining sections (A–A’, B–B’, E–E’, and F–F’) have FS values below the critical threshold of 1.3. Specifically, sections E–E’and F–F’ showed very low FS values, confirming that the presence of mud is the dominant factor causing instability. This indicates that most of the dump slopes are at high risk of failure and categorized as unsafe. Consequently, these analysis results provide a critical foundation for consideration in the planning of future slope geometry redesigns