Golder was engaged to undertake a feasibility-level slope design for the open pit at Elang, a large copper porphyry deposit in Sumbawa, Indonesia.
A multi-disciplinary team from Australia and Indonesia included rock mechanics specialists, hydrogeologists and geophysicists who undertook the design and oversaw quality assurance and quality control on the drilling program and laboratory testing campaign.
One of the biggest technical challenges on a large open pit project is ensuring slope stability. Collecting reliable structural data is essential. To do so, Golder employed a method that is generally more reliable and less error-prone than traditional techniques. Structural information was collected using downhole Acoustic Televiewer (ATV) survey, which could be interpreted off site and used to map structural features.
Downhole sonic logging data was used to verify boundaries between weathered and transitional rocks and to assist with developing surfaces for 3D modelling of design domains. This sonic logging information can be used as a proxy for density with resolution often down to less than 0.01 mm. Vulcan 3D modelling software was used in all aspects of the design to spatially characterise design domains and optimise slope angles.
Golder’s detailed geotechnical work on the characterisation of materials (with input from geophysical sources) ensured that the design recommendations appropriately reflected the material competency. This ensured a safe design as well as optimisation where applicable.
Even minor increases in slope angles in such a large open pit can make or break a project due to sensitivity to stripping ratios. Golder’s approach to the optimisation saved costs on earth-moving time and equipment. It also achieved a smaller footprint with associated reductions in emissions and a reduced environmental impact.
Delivering on scope and within budget enabled the client to secure investment and move forward to the next stage of development.