Geotechnical aspects of eroded sediments relevant to tailings disposal design.

Abstract

Since 1975, Samarco Minerac¸a˜o S.A. has been mining the iron ore deposits of the Germano Mine in the Quadrila´tero Ferrı´fero ~Iron Quadrangle! in Minas Gerais, Brazil. Presently, this mine is depleted, and a huge ultimate pit ~approximately 1,300 m long, 800 m wide, and 220 m deep!, known as the Germano Open Pit, was produced. Samarco Minerac¸a˜o currently processes the iron ore from the adjacent Alegria Mine, having reserves that exceed 5 billion tons of itabirite. The iron ore is transported by a 1,500-m-long conveyor belt that crosses the eastern border of the Germano Pit. Design studies of the tailings disposal system to be implemented in this old pit area have generated several questions related to the geological complexity and geotechnical features of the pit and the engineering properties of the tailings. The proposed project will fill the abandoned pit with tailings using the upstream construction method and will reach up to 160 m high when completed. The paper discusses the geological and geotechnical concerns regarding instability of slopes and deposited sediments. These studies are essential for evaluation of the deposited sediments as a foundation material for future tailings pile structures.