Soil formation from tailings: comparison of predictions and field measurements

Abstract

The extraction and processing of most mineral ores results in the generation of large volumes of fine-grained residue or tailings. The safe disposal of such material, which generally exhibits slow rates of sedimentation and consolidation, is of prime concern to the management of mining operations. In order to devise both long- and short-term options, it is necessary to have an understanding of the transportation, sedimentation and consolidation characteristics of the residue material, which may be impounded behind specially designed dams. The processes of transport of sediments, sedimentation and consolidation take place simultaneously in the reservoirs formed behind dams. The objective of this study is to analyse the coupled phenomena of soil formation to estimate accurately the capacity of a reservoir when waste material is impounded. An implicit finite difference analysis was developed to solve the transport of sediments and sedimentation problem. Linked to this procedure, a finite element analysis of the consolidation processes is introduced considering geometrical and material non-linearity, through the use, respectively, of a Eulerian rate viewpoint and a non-linear elastic constitutive model. The complete process is analysed in a step-by-step methodology. This paper compares numerical results with field measurements during the disposal of bauxite mine tailings. The numerical analysis successfully predicts the filling of the reservoir and the void ratio profile.