Caracterização geotécnica e avaliação da compactação de um resíduo da produção de alumina (lama vermelha) desaguado por filtro prensa

Abstract

One of the technologies that have been studied currently for the disposition of mining wastes and tailings is their filtration by press filters. In this solution, the residue is pumped under high pressure by permeable filtering elements, which allow the passage of water while retaining the solid in filtering plates, forming compacted cakes with high solids content (from 70% to 80%) and degree of saturation of approximately 80%. Thus, it is necessary to study the characteristics and behavior of the filtered residue to design the best and safest form of their disposal. This research presents the geotechnical characterization of a residue from alumina production, called red mud, that was dewatered by press filter, as well as its behavior when compacted to construct piles and landfills. Laboratory tests were conducted on disturbed samples of the residue collected at the output of a press filter pilot. A field test was conducted to evaluate the compaction of residue dewatered by press filter, using tracked equipment. Undisturbed samples were taken from this pilot landfill and tested in the laboratory. The methodology for implementation of the test area and the field results obtained were presented by NERY et al, 2013. The laboratory results showed that the moisture content of the residue at the output of the press filter is equivalent to the optimum moisture content of the material, which facilitates the direct compaction in the disposal area. After compacted, the residue has low permeability, in the order of 10-8 to 10-10 m/s. These results were measured using undisturbed specimens collected from the field with degree of compaction between 90% to 100% and the moisture content at 5 % below and above the optimum moisture content. The strength parameters were also obtained by triaxial UU (Unconsolidated and Undrained) tests in unsaturated samples, because it is expected that this residue should will not saturate after its disposition.