Heap leaching is a widely used technique for copper extraction, generating large volumes of spent ore typically deposited in sizable waste dumps, sometimes exceeding 150 meters in height. The loose and contractive nature of these deposits, combined with high moisture content and potential chemical alteration, raises concerns about their physical stability—especially regarding flow (static) liquefaction.
This study evaluates the vulnerability of a representative spent ore dump to flow liquefaction using finite element modeling, specifically employing the NorSand constitutive model to simulate undrained behavior under varied loading and saturation scenarios. Triggers examined include rises in phreatic level and rapid load increments at the at the lower bench.
Results indicate that failure occurs when the phreatic level rises to 5 m above the dump base, whereas for lower elevations, loads of up to approximately 70 kPa are required to induce localized instability under undrained conditions. Complete liquefaction of the deposit is improbable under the conditions modeled; however, localized zones of saturation and strength loss can present hazard to operations and nearby activities.
The study underscores the importance of drainage system functionality, routine monitoring of saturation levels, and implementation of threshold load criteria to ensure safe operation. Constitutive modeling NorSand provided reproduction of observed failure mechanisms and pore pressure evolution.
The findings highlight the need for robust geotechnical control practices in the design, monitoring, and operation of spent ore dumps to minimize the risk of flow liquefaction and its potential consequences.
