Electronic Theses and Dissertation

Kestabilan lereng pada tambang terbuka merupakan aspek penting yang
memengaruhi keselamatan kerja dan kelancaran operasi. Infiltrasi hujan dapat
meningkatkan tekanan air pori, menurunkan tegangan efektif, dan melemahkan
kekuatan geser tanah sehingga menurunkan stabilitas lereng. Penelitian ini
bertujuan menganalisis pengaruh infiltrasi hujan terhadap kestabilan lereng
disposal di PT Antareja Mahada Makmur jobsite PT Mifa Bersaudara
menggunakan metode elemen hingga (Finite Element Method) melalui perangkat
lunak Plaxis 2D. Pemodelan dilakukan dengan model Mohr–Coulomb berdasarkan
parameter tanah dan geometri aktual pada kondisi kering, setengah jenuh, dan
jenuh. Hasil analisis pada seluruh lereng (AA’, BB’, dan CC’) menunjukkan bahwa
nilai faktor keamanan menurun seiring meningkatnya tingkat kejenuhan tanah.
Nilai tertinggi diperoleh pada kondisi kering, menurun pada kondisi setengah jenuh,
dan mencapai nilai terendah pada kondisi jenuh akibat peningkatan tekanan air pori
dan penurunan kekuatan geser tanah. Meskipun seluruh lereng masih berada dalam
kategori stabil, peningkatan kejenuhan membuat lereng lebih sensitif terhadap
perubahan kondisi hidrologi, sehingga diperlukan pemantauan curah hujan dan
muka air tanah secara berkelanjutan.

Slope stability in open-pit mining is a critical aspect affecting operational continuity and workplace safety. Rainfall infiltration can increase pore water pressure, reduce effective stress, and weaken soil shear strength, leading to a decrease in slope stability. This study aims to analyze the effect of rainfall infiltration on the stability of disposal slopes at PT Antareja Mahada Makmur, PT Mifa Bersaudara jobsite, using the Finite Element Method (FEM) through Plaxis 2D software. The modeling was conducted using the Mohr–Coulomb model based on soil parameters and actual slope geometry under dry, partially saturated, and fully saturated conditions. The analysis results for all investigated slopes (AA’, BB’, and CC’) indicate that the factor of safety decreases with increasing soil saturation. The highest factor of safety is obtained under dry conditions, decreases under partially saturated conditions, and reaches the lowest value under fully saturated conditions due to increased pore water pressure and reduced soil shear strength. Although all slopes remain in a stable condition, increased saturation makes the slopes more sensitive to hydrological changes; therefore, continuous monitoring of rainfall and groundwater levels is required.