Compaction Sensitivity in Tailings Stack Infiltration Modeling: Unsaturated Properties Uncertainty Analysis
Authors: Letícia B. L. Garcia1, Marcos A. Lemos Júnior2, Guilherme J. C. Gomes3
Conference: Tailings and Mine Waste 2024
Date: November 10-13, 2024
1 Knight Piésold Consultoria Ltda., Brazil
2 Companhia Brasileira de Metalurgia e Mineração (CBMM), Brazil
3 Universidade Federal de Ouro Preto (UFOP), Brazil
ABSTRACT
Filtered tailings stacks have become increasingly prevalent in the mining industry since the 1990s, particularly in regions with arid climates. However, the adoption of filtered tailings technology has expanded globally, regardless of climatic conditions, as mining operations seek to reduce water in tailings to improve safety. Nonetheless, the implementation of tailings stacks in high-rainfall areas contradicts conventional practices, as filtered tailings operations are typically associated with regions of low precipitation due to compaction challenges during rainy periods. This poses significant challenges for tailings stacking in high-rainfall conditions, including their unsaturated characteristics and the absence of specific guidelines tailored to such environments.
Consequently, numerical modeling of infiltration under the principles of Unsaturated Soil Mechanics offers a promising approach to optimize recharge calculations, enabling more precise assessment of various factors such as moisture content, compaction, and drain sizing for these stacks. While optimized values are expected through modeling, inherent uncertainties exist in calibrating soil water retention curves (SWCC) and permeability functions, which involve Van Genuchten parameters, thereby affecting both parameter definition and model results. This study utilized tailings properties from a Brazilian mine, along with site climatic data, and employed a Bayesian approach to address calibration uncertainties. A hypothetical two-dimensional (2D) section of a test pad was considered for the study, and a software that simulates the movement of water and solutes in variably saturated media, for obtaining infiltration rates by solving the Richards Equation, was employed. In addition to calibration uncertainties, the simulation assessed the compaction sensitivity (different void ratios) on the SWCC, revealing that both factors influenced infiltration rates and pressure head fluctuations. These findings underscore the critical importance of proper compaction control and suitable drainage system design.
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