Coupled hydro-mechanical analysis and stabilization of a failing heap leaching structure

Abstract

Heap leaching structures are subject to continuous changes during operation due to the combined influence of hydro-geomechanical and chemical parameters. These changes may impact heap stability and potentially lead to failure. This study investigates the geotechnical instability of a heap leaching structure, emphasizing mechanisms of failure and proposing effective stabilization strategies to enhance operational safety and environmental resilience. Over a four-month monitoring period, the studied heap exhibited a displacement of approximately 2.5 m towards the collection ditch. To identify failure mechanisms and critical zones, a multidisciplinary approach integrating geophysical surveys, borehole drilling, and coupled hydro-mechanical numerical modelling was employed. The simulations replicated observed plastic deformations and delineated critical failure zones. Sensitivity analyses were conducted on cohesion, Young’s modulus, and Poisson’s ratio. Results indicated that reducing cohesion below 29 kPa significantly increases instability risk, while a Young’s modulus of 10 MPa closely matched the 2.3 m displacement observed in field surveys. Laboratory tests and simulations revealed fluid accumulation, elevated pore pressure, and acid-induced shear strength reduction as the primary displacement drivers. A stabilization strategy combining toe reinforcement and load reduction at the crest was designed, simulated, and implemented. This approach effectively reduced plastic deformations and displacement, restoring the heap’s structural stability. The study underscores the importance of integrating field observations, numerical modelling, and parameter sensitivity analysis for diagnosing and mitigating failure in heap leaching structures.