Unsaturated shear strength parameters for a compacted iron ore tailings

¹ Master's student at IGC-USP, São Paulo, Brazil
² Engineer at the Technological Research Institute of the State of São Paulo (IPT) and Master's student at IGC-USP, Brazil.
³ Engineer at Vale S.A., Minas Gerais, Brazil.
⁴ Associate Professor at USP, São Paulo, Brazil

Abstract

The use of iron mining tailings in compacted landfills is expected to expand more and more to replace the placement of tailings in dams. With this, the unsaturated condition of these materials becomes of great importance for the safety of the structures executed with them. In addition to tests in the saturated condition, and with the objective of simplifying the determination of strength parameters in the unsaturated condition, direct shear tests with constant water content were performed. Data of physical and chemical characterization of the tailings, and the water retention curve at the compacted state and continuously disturbed condition are also presented. The latter aims to evaluate the effect of the shear process on the final suction of the material. The results suggest that there are no significant variations in suctions during the failure process and that, in this case, the initial suction can be assumed to be the same as the one at failure. The shear strength parameters indicate a high friction angle, which does not vary with suction. With the data obtained, it was possible to apply the model of Vilar (2006) to obtain the shear envelope with suction. The results presented aim not only to expand the database of iron ore tailings parameters, but also to present a procedure for the application of tests with constant water content.