Methodology or Approach This paper examines the tailings material characterization requirements and geotechnical design considerations for filtered tailings stacks with the overarching goal of enhancing safety, water recovery, and operational performance. The scope encompasses both the fundamental material properties that influence filtration behaviour—such as particle size distribution, moisture retention characteristics, and unsaturated shear strength—and the operational and environmental conditions that govern how these materials perform once placed in a stack. It places particular emphasis on understanding how moisture variability, matric suction, compaction practices, and stack geometry interact to control stability and trafficability over the life of the facility. By establishing these characterization and design requirements, this paper seeks to support more reliable implementation of filtered tailings systems, reduce uncertainty in stability assessments, and promote practices that optimize dewatering efficiency, environmental performance, and long‑term facility integrity. Key Results, Outcomes, or Insights 1. Material Characterization for Filterability and Performance Material characterization is one of the most critical aspects of filtered tailings design, as the geotechnical, mineralogical, and rheological properties of the tailings directly influence dewatering efficiency, stack performance, trafficability, and long-term stability. Comprehensive laboratory and field testing allow engineers to define filtration expectations, compaction requirements, drainage needs, and stability parameters. Because filtered tailings operate under partially saturated conditions, slight variations in material behaviour can lead to significant differences in field performance—making a thorough characterization program essential before technology selection and stack design. 1.1. Particle Size Distribution (PSD) PSD strongly governs the filterability, moisture retention, and hydraulic conductivity of tailings. Key considerations include: • Fine fraction (< 75 µm): Dewatering becomes increasingly challenging when fines exceed ~50%, as finer particles reduce permeability and tend to clog filter media. • Coarse-to-fine balance: Coarser fractions promote faster drainage and higher achievable cake dryness, while high fines content yields slower filtration cycles and wetter cakes. • Heterogeneity: Variability in PSD over the life of mine must be captured, as changes in ore mineralogy affect dewatering plant performance and compaction behaviour in the stack. • Implications for design: PSD influences stacking geometry, achievable densities, required compaction energy, and erosion susceptibility. As part of their development of a geotechnically derived screening method for assessing tailings filterability, Meneses et al. (2024) conducted an extensive review of published particle size distribution (PSD) data for a wide range of tailings types. PSD plays a critical role in evaluating filtration performance because particle size directly influences both cake formation and drainage efficiency during mechanical dewatering. In general, a higher proportion of fine particles can hinder cake development, restrict drainage pathways, and result in slower filtration rates and
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