Aplicação geotécnica de resíduo de mineração em sistemas de cobertura final de aterros sanitários

Abstract

The use of mining residues within production chains, such as civil construction, is an important environmental solution for mining activities in Brazil. Researchers have shown that different types of mining residues can be incorporated into some types of geotechnical works, fulfilling the function of hydraulic barrier. In this scenario, the use of scheelite residue in environmental geotechnics works could be an environmentally sustainable solution for this material. This work aims to evaluate the technical viability of using two scheelita mining residues as a compacted coating with hydraulic barrier function in waste landfill covering systems. Physical characterization, compacting, hydraulic conductivity on rigid and flexible wall permeameters, XRF/XRD and SEM and erodibility tests were performed on four materials formed by mixing two residues generated during the scheelite processing at the Brejuí Mine in Currais Novos/RN. In the tests, samples were conformed by the two residues used, varying from the fine residue exclusively, and departing for variations of 25% by mass of the coarse residue content (F100, F75G25, F50G50 and F25G75). The obtained results demonstrate the technical viability of the intended use of the material. The F100 and F75G25 samples proved to be viable for the intended application (hydraulic barrier in landfill covering), meeting international normative requirements. The other composites (F50G50 and F25G75) could be applied for other purposes within a waste landfill: as regularization and/or protection layers. During the hydraulic conductivity tests, it was observed that, in the samples that contained a higher percentage of fine particles (< 0,075 mm), there was a progressive decrease in the permeability of the compacted material, from 1,76x10-6 to 2,18x10-8 m/s, but not necessarily a significant variation in the density or porosity, indicating that the incorporated fines filled the voids of the larger particles increasing the flow tortuosity. The decrease in permeability can be explained by morphological factors specific to the material used.