Analysis of Pore Structure Evolution and Leaching Effectiveness in Ore Granular Materials During Stope Leaching

In situ stope leaching is an economically and environmentally friendly metal recovery method suitable for low-grade copper ores, with the internal temperature of the deposit typically ranging from 30 to 45 °C. The fragmented ore with a specific particle size distribution formed after blasting constitutes a complex pore structure, which provides channels for acid solution infiltration and chemical reactions, directly affecting leaching efficiency. To reveal the spatiotemporal heterogeneity of pore structure evolution during leaching at the microscopic level and its fundamental impact on macroscopic permeability and leaching rate, leaching experiments were conducted using acid leaching methods based on ore particle models with different size distributions. Computed Tomography (CT) scanning technology and Avizo 2023 software were employed to scan and reconstruct three-dimensional physical models, enabling quantitative calculation and analysis of the evolutionary patterns of pore structure parameters. These results were then correlated with the measured leaching rate evolution. The findings indicate that both the connectivity and overall volumetric porosity of the stope models for Sample 1 (2–20 mm, uniformly graded) and Sample 2 (0–20 mm, high fine particle content) continuously decreased during leaching, with a more pronounced decline in the lower regions, particularly for Sample 2. The pore-throat sizes of both models increased with leaching time, and after 45 days of leaching, the average pore radius of the two granular ore samples increased by 16.75% and 9.21%, respectively. The leaching rate showed a high correlation with the effective reaction area (R2 = 0.93). During the 0–15-day period, a sharp decline in the effective reaction area led to a rapid decrease in leaching efficiency. Sample 1 exhibited a longer effective leaching duration, achieving a leaching rate of 61%, significantly higher than that of Sample 2.