Probability of Failure and Slope Safety Factors Based on Geological Structure of Plane failure on Open Pit Batu Hijau Nusa Tenggara Barat

Abstract

Batu Hijau is a gold mine which is now run and managed by PT Amman Mineral Nusa Tenggara (PT AMNT) with open mining method. The located in Sekongkang District, West Sumbawa Regency - West Nusa Tenggara Province. The geological structure aspects are interesting as objects in this study, due to the condition is very tight and become to trigger for the slope failure. Slope stability is one of the important terms for supporting in open pit mining activities. One of the slope failure indication is the failure caused by the structure. Geological structure analysis performed with kinematic analysis which takes into account the probability of failure and type of failure. The probability of Failure can count by structure orientation, the orientation of the mine slope design, and friction angle with using dips 6 software. The percentage of slide obtained from the ratio between the critical point from the critical zone with the total critical point in stereographic projection. The count applied in all geotechnics domain with inputting of parameter structure orientation, the orientation of the mine slope design, and friction angle. The result shows between 0% to 2.63% of planar failure. The percentages show probability of failure but still in the safe category with 10% safety limit. Slope safety factor counts manually based on the mathematical formula applied to all domains in Batu Hijau Open Pit Mining. The result shows the value between 1.04 to 1.905 on planar failure. This value shows the condition of slope in the research site is stable.