Seepage mechanism during in-situ leaching process of weathered crust elution-deposited rare earth ores with magnesium salt

To reveal seepage mechanism during in-situ leaching process of weathered crust elution deposited rare earth ores with magnesium salt, the effects of particle gradation, particle migration, Atterberg limit on the permeability coefficient were investigated, and the relation between the particle size and rare earth content was discussed. The results showed that the ore in the humic layer (HL) with high porosity and permeability was uniformly graded particles. The ore in the completely weathered layer (CWL) with low porosity and permeability belonged to dense-graded particles. The ore in the partly weathered layer (PWL) was open-graded particles, whose permeability fell in between the HL and the PWL. The change of -0.075mm particles content was the largest in the leaching process. When - 0.075mm particle content was less than 30%, the migration ability of fine particles and the permeability coefficient decreased gradually. On the contrary, the migration ability of fine particles gradually remained stable, and the change in the permeability coefficient was not obvious. The liquid limit (LL) in the Atterberg limit of HL, CWL and PWL was inversely proportional to the permeability coefficient, and followed the order: LL_HL < LL_PWL < LL_CWL. With the -0.075mm particle content increasing, the LL of the ore samples increased gradually and finally tended to be stable. The peak value of rare earth concentration appeared earlier and the rare earth content decreased gradually with the increase of the ore particle size. This work provided a theoretical basis for achieving high-efficient mining of weathered crust elution-deposited rare earth ores.