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Título

ASSESSMENT OF THE HYDRAULIC PROPERTIES OF IRON ORE TAILINGS FOR MINING CLOSURE PROJECTS IN BRAZIL

Resumo

Recent disasters with tailings dams raised by the upstream method have resulted in modifications to the legislation regarding tailings disposal. New regulations require these structures to be properly decommissioned. Closure projects require changes in the original structure to increase safety and reduce risk. This safer condition is usually achieved by removing materials from the original dam. These materials, afterward, can be stored as dry stacks using filtered and compacted materials. The materials in stacks will usually be unsaturated. Also, the use of dry stacking has been successfully addressed for arid areas for a long but lacks more data for structures in tropical climate areas. This study focused on assessing the hydraulic properties of three types of tailings (named A, B, and C) collected from a tailings’ impoundment in Brazil at distinct stages of saturation. Then, permeability tests were performed using a flexible wall permeameter in different stages of degree of saturation, starting from 100%, considering the conditions of the tailings dams, and then decreasing the degree of saturation to account for the unsaturated behavior of tailings in dry stacks. The diffusivity, volumetric water content, and hydraulic conductivity of the tailings were studied and the changes in them showed similar trends for tailings B and C. However, tailings A exhibited some differences by displaying higher diffusivity and volumetric water content throughout the test, along with lower hydraulic conductivity, which remained relatively consistent during the entire test. Tailings A had the lowest saturated hydraulic conductivity as well.

Palavras-chave

Mining closure, tailings, permeability, hydraulic conductivity, volumetric water content, diffusivity.

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