Characterization of liquid seepage hysteresis and capillary diffusion behavior in unsaturated ore heap

To deeply understand the capillary diffusion and seepage hysteresis behavior of the leaching solution in unsaturated ore heaps, this study builds a capillary seepage model suitable for an unsaturated ore heap by employing the COMSOL multiphysics finite element numerical platform to perform the capillary seepage visual simulation. A time-domain reflector is used to detect in-situ liquid holdup changes in the unsaturated heap in real-time, and multifactor response regulations of the capillary seepage process are explored based on a design expert. The potential connection mechanism among the liquid holdup, capillary suction, porosity, and irrigation rate of unsaturated ore heaps is also discussed. Research results show that the heap porosity has an obvious impact on the heap liquid holdup than the irrigation intensity. The increased convergence of the liquid holdup improves with the spraying time, and the ore heap with small porosity takes a longer time to reach a steady status of the liquid holdup. When the effect of the liquid irrigation is not considered, the heap liquid holdup is positively correlated with the porosity ratio and hydraulic conductivity. Especially in the initial stage of the irrigation period (0–20 s), the effects of the irrigation rate, hydraulic conductivity, and porosity ratio on the ore heap liquid holdup are more significant. An unsaturated ore pile solution capillary seepage model considering the gas−liquid two-phase migration is preliminarily constructed. The capillary suction is observed to be more sensitive in the ore heap with lesser porosity. The larger the irrigation rate and the smaller the porosity, the greater is the capillary suction at the bottom of the ore heap, and it is easier for the ore heap to reach a steady state of the liquid holdup.