Mechanism Analysis and Control Strategy of Pore Structure Evolution in Granular Ore Media During Heap Leaching Process

Heap leaching efficiency is constrained by the non-uniform seepage of the leaching solution (such as sulphuric acid), where preferential flow and localized plugging lead to low leaching rates, prolonged cycles, and high acid consumption. Seepage behavior is fundamentally governed by pore structure, which evolves continuously during leaching through chemical dissolution and physical plugging, and in turn feeds back to affect reactive transport by altering seepage pathways. Taking low-grade copper oxide ore (0.58%) as the research object, this study systematically investigates the chemical–physical coupling mechanisms of pore structure evolution and the corresponding regulation strategies through column leaching experiments, shrinking-core kinetics analysis, migration-plugging analysis, and COMSOL multi-physics coupling simulation. The results indicate that copper leaching is jointly controlled by chemical reaction and diffusion, with the apparent rate constant following a power-law relationship with acid concentration (reaction order n = 0.65), demonstrating significantly diminishing marginal gains. Physical plugging is identified as a critical factor in the sharp decline of permeability, with the hydraulic conductivity of the 0.2 mm particle size group decreasing by 86.58%, far exceeding the 37.80% reduction observed in the 0.05 mm group. On this basis, chemical–physical coupling mechanism analysis reveals the competitive control of four mechanisms over pore evolution: dissolution-induced pore enlargement, precipitation-induced pore shrinkage, plugging-induced pore shrinkage, and collapse-induced pore shrinkage. A COMSOL-based multi-physics coupling model integrating seepage, reaction, migration, and mechanics is constructed to predict porosity, permeability, and leaching rate during the leaching process, with model errors below 10%. The temporal contribution rates of the four mechanisms reveal a three-stage evolution pattern: a dissolution-dominated stage in the early period, a multi-mechanism competitive stage in the middle period, and a precipitation-plugging synergistic densification stage (accounting for >90% in total) in the later period. Accordingly, a phased spray regulation strategy is proposed, achieving a leaching rate exceeding 65% under uniform flow velocity conditions. This study provides a theoretical basis and numerical tools for enhancing the leaching efficiency of low-grade copper ores.