Large strain consolidation analyses of fine tailings disposal in mining pits

Abstract

Herein, three-dimensional analyses of large strain consolidation applied to tailings disposal in mining pits is studied. The main goal is to estimate filling time and, accordingly, the capacity of the pit. Other useful results, such as dry density profiles and water pore pressure generation are also obtained. Two different slimes from the iron ore beneficiation are considered: a low plastic silt-clay material, and a 10 times more permeable silt-like soil. The consolidation constitutive relationships were obtained by performing HCT tests (Hydraulic Consolidation Test). The analyses were carried out using an algorithm that produces approximate solutions of the three-dimensional analysis using the computer program CONDES0. Two types of analyses were performed limiting the exact solution, one called upper bound and the other, lower bound. For purposes of this study, sensitivity analyses were also performed, including "instantaneous" consolidation, double drainage, and varying tailings production. Simulations of the co-disposal of the two different slimes were also addressed, where simultaneous rising and sharing of the tailings during reservoir occupation were sought by trial and error. In addition, prediction of the deposit surface profile in the long-term run was included. It was obtained from the filling of the pit with the Slime 01 for the lower bound 1054 days and for the upper bound, 1219 days. By comparing the slimes, Slime 02 offers the greater capacity. In the scenario of co-disposition, Slime 01 occupies 43% of the area and Slime 02, 57% of the area of the pit. Having already analyzed scenarios with constant and variable production of Slime 01 a greater capacity of the pit was obtained for a constant production. Finally, there is a small difference in the pit capacity when the analyses are made considering the impermeable base and the permeable base.

Estimating the Potential Differential Settlement of a Tailings Deposit Based on Consolidation Properties Heterogeneity

“…The quasi-3D model does not consider the lateral influences among the columns or between columns and facility side walls, as should be considered in real 3D consolidation modeling. This modeling approach has been replicated in the literature, for example in [18,19], and is a valid approach when the goal is to have an early estimation of the potential surface or expected differential settlement in the deposit for long-term decisions where high accuracy of the results is not intended. It is assumed that all 25 columns at the defined points have the same bottom elevation.…”

“…A one-dimensional (1D) column consolidation is the basis for most of the current modeling practices and has been extrapolated to the whole deposits' consolidation behavior [16][17][18]. Another example of approximating the 3D consolidation based on a 1D large strain model is presented in [19], which studied the 3D analysis of a large strain consolidation model for tailings that are deposited in a mining pit. The goal was to estimate the filling time and tailings storage capacity.…”