Analisa Kestabilan Lereng Disposal Menggunakan Metode Kesetimbangan Batas di Tambang Nikel Kabupaten Konawe, Provinsi Sulawesi Tenggara

Abstract

Abstract. The company, which is located in the Konawe district, is engaged in the nickel mining industry in Southeast Sulawesi with an open pit mining system. The rocks that make up the research site are ultramafic ophiolites, which have weathered dominated by peridotite, harzburgite which are serpentinized and are characterized by the type of laterite nickel deposits. Nickel mining companies operating in block a want to know the geometric design of disposal slopes to achieve slope stability. Factors that affect slope stability are: rock characteristics (physical-mechanical properties), factors from outside the slope system such as earthquakes, slope geometry and so on. The laboratory test results of the physical properties of bedrock, namely average natural density = 2,29 gr/cm3 and disposal material = 1,75 gr/cm3. While the test results of the mechanical properties of bedrock, namely the average cohesion of 353,95 kPa, and the inner shear angle = 29,13°. Disposal material has an average cohesion value of 49,2 kPa, and the inner sliding angle value = 21,40°. The simulation results of the single slope stability analysis produce a single slope geometry with a height of 5 m and a slope angle of 35°. The geometry of the single slope is stable and safe with the FK value = 2,589 and the PK value = 0%. The recommended overall slope design in saturated conditions is an overall height of 25 m with an overall slope of 20 °. The overall slope geometry is stable and safe with FK value = 1,131 and PK value = 0%. The results of the analysis of the stability of the bedrock obtained the value of FK = 2,828 with PK = 0%, so it is stated that the subgrade in a stable state can withstand the disposal load on it.

Keywords: disposal slope, rock characteristics, slope stability, bedrock stability

Abstrak. Perusahaan yang berlokasi di kabuaten Konawe ini bergerak di industri pertambangan nikel di Sulawesi Tenggara dengan sistem penambangan tambang terbuka. Batuan penyusun lokasi peneltian adalah batuan ultramafik ofiolit yang mengalami pelapukan didominasi oleh peridotit, harzburgite yang terserpentinisasi dan memiliki ciri-ciri tipe endapan nikel laterit. Perusahaan tambang nikel yang beroperasi pada blok A ingin mengetahui perancangan geometri lereng disposal untuk mencapai kestabilan lereng. Faktor yang mempengaruhi kestabilan lereng yaitu: karakteristik batuan (sifat fisik-mekanik), faktor dari luar sistem lereng seperti gempa, geometri lereng dan sebagainya. Hasil uji laboratorium sifat fisik batuan dasar (bedrock), yaitu natural density rata-rata = 2,29 gr/cm³ dan material disposal = 1,75 gr/cm³. Sedangkan hasil uji sifat mekanik batuan dasar, yaitu kohesi rata-rata sebesar 353,95 kPa, dan sudut geser dalam = 29,13°. Material disposal mempunyai nilai kohesi rata-rata sebesar 49,2 kPa, dan nilai sudut geser dalam = 21,40°.vHasil simulasi analisis stabilitas lereng tunggal menghasilkan geometri lereng tunggal tinggi 5 m, dan sudut kemiringan 35°. Geometri lereng tunggal tersebut dalam keadaan stabil dan aman dengan nilai FK= 2,589 dan nilai PK= 0%. Rekomendasi desain lereng keseluruhan dalam kondisi jenuh yaitu, tinggi keseluruhan 25 m dengan kemiringan keseluruhan (overall slope) 20°. Geometri lereng keseluruhan tersebut dalam keadaan stabil dan aman dengan nilai FK= 1,131 dan nilai PK= 0%. Hasil analisis stabilitas batuan dasar didapatkan nilai FK= 2.828 dengan PK= 0%,  sehingga dinyatakan tanah dasar dalam keadaan stabil mampu menahan beban disposal di atasnya. 

Kata Kunci : lereng disposal, karakteristik batuan, kestabilan lereng, stabilitas batuan dasar