Sensitivity Analysis of Phase 5 Batu Hijau Pit Walls

Khatib Syarbini; Andi Faesal; Za Munarfan Putra; Syamsul Hidayat; Wahyu Hermansyah; Melinda Dwi Erintina; Aji Syailendra Ubaidillah; Iwan Dermawan; Uraihan Azhari; Muhammad Samsul Hakim

doi:10.25299/jgeet.2025.10.02.21571

Authors

Khatib Syarbini Geological Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Andi Faesal Geological Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Za Munarfan Putra Geological Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Syamsul Hidayat Mining Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Wahyu Hermansyah Geological Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Melinda Dwi Erintina Mining Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Aji Syailendra Ubaidillah Mining Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Iwan Dermawan Geological Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Uraihan Azhari Mining Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia
Muhammad Samsul Hakim Geological Engineering Department, Universitas Muhammadiyah Mataram, 83115 Mataram City, Indonesia

DOI:

https://doi.org/10.25299/jgeet.2025.10.02.21571

Keywords:

Batu Hijau, Rock Mass Rating, Groundwater, Water Pressure, Rock Mass

Abstract

The Batu Hijau mine, an extensive copper-gold operation in West Sumbawa, Indonesia, employs an open-pit mining method and is characterized by its significant pit dimensions, with planned slope heights reaching up to 1000 meters. Given the scale of the operation, maintaining slope stability is critical, influenced by stress on the pit slopes, geological structures, mine geometry, and rock mass strength. This study investigates the impact of groundwater on slope stability, emphasizing the role of groundwater pressure in reducing shear strength and consequently affecting slope stability.

A comprehensive sensitivity analysis was conducted to evaluate the influence of groundwater pressures on the stability of the Batu Hijau pit walls. This analysis utilized the SLIDE® software from Rocsience, incorporating Rock Mass Rating parameters derived from geotechnical drill hole logs and mapping data, which were integrated into a 3D block model using Minesight™. The analysis focused on two groundwater conditions: Water Surface and Pore Pressure Grid. Groundwater model conditions were based on piezometer data and a new groundwater conceptual model of the Batu Hijau pit walls.

Results from sensitivity assessments shows that high pore pressure will decease the slope stability. This findings highlight the need to manage groundwater pressures within the pit walls to mitigate slope instability effectively,therefore, the safety of mining operational could be increased. This study provides valuable insights into groundwater pressure management and its implications for slope stability in large-scale open-pit mining operations.

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