The multifaceted geopolitical, financial, cultural, and social importance of gold to nations has prompted a growing emphasis on sustainable extraction methods. As deposits of high-grade gold become increasingly depleted, processing low-grade minerals has become increasingly significant in mitigating the environmental impacts of deep mining. Heap leaching is recognized as an economically viable and environmentally friendly method for extracting gold, silver, and nickel. Crushed gold ores are stacked on slopes, which are covered by impermeable pads, and sulfuric acid (H₂SO₄) is sprayed on the ores to extract precious metals. Despite its advantages, pad damage in heap leaching poses contamination risks to groundwater resources. To investigate the effects of acid penetration through rock joints and faults at heap leaching sites, we conducted a multi-scale study (2 mm–20 m) based on realistic data from a heap leaching site. A self-designed autoclave was constructed to evaluate the mechanical and hydraulic characteristics of rocks exposed to acidic solutions with pH and temperature values similar to those found at the heap leaching site. The exposure time was set at three weeks, which is comparable to the average time required for detecting pad damage. The laboratory data were combined with SEM imaging and field evaluations. The resulting multi-scale data were used to develop a chemical damage model, which was upscaled through numerical simulations (within a 20 m × 20 m area) to assess field-scale scenarios. pH changes associated with sulfuric acid solutions resulted in fluid flow rates three to five times higher for pH values of 5 and 1, respectively. Consequently, acidic solutions can travel significant distances through groundwater or surface water, potentially reaching up to 60–80 km from the initial leakage source. This contamination adversely affects water quality and human communities, with exposure to sulfuric acid solutions potentially leading to health problems such as gastrointestinal disorders, esophageal damage, respiratory issues, and metabolic acidosis. Therefore, despite the economic and environmental advantages, comprehensive studies on lithology, large-scale fractures, and proximity to residential areas are pivotal before choosing heap leaching sites. Additionally, regular inspections of pad conditions can reduce the risk of damage and exposure time. Our study highlights that a sustainable technique can lead to an environmental disaster without proper oversight and preliminary studies.
 

Heap leaching,slope stability