886 tailings (Grosso et al., 2021), gradation envelopes for dry‑stack operations (Crystal & Hore, 2018), gold tailings (Burden, 2021), graphite tailings (Moshi et al., 2019), polymetallic tailings from the Hecla Creek TDF (Erickson et al., 2021), and iron ore tailings from multiple sites (Costa et al., 2021; Amoah et al., 2018). By consolidating these sources, Meneses et al. (2024) establish a comparative PSD baseline that illustrates how different tailings materials align with or deviate from filtration performance thresholds. This benchmarking step forms a key component of their first‑pass filterability screening approach. Figure 2: Geotechnical Screening Method to Assess Filtration of Tailings (after Meness et al., 2024) 1.2. Clay Mineralogy and Atterberg Limits Clay content and mineralogy—particularly the presence of smectite or bentonitic clays—play a dominant role in tailings plasticity, suction behavior, and filter performance. Key insights: • Clay mineral type affects swelling potential, water adsorption, and shrink–swell behaviour under cyclic wetting/drying. • Atterberg limits provide indicators of plasticity; high plasticity index (PI) tailings exhibit lower permeability and may form weaker cake structures with higher residual moisture. • Suction sensitivity: Clay-rich tailings may undergo significant strength loss with small increases in degree of saturation—crucial for unsaturated stability assessments. • Operational risk: High clay content may require blending, pre-drying, or different filtration technologies to achieve acceptable moisture contents. 2. Geotechnical Design Considerations for Filtered Tailings Stacks Filtered stacks are formed by placing dewatered tailings in compacted lifts over an engineered foundation, and, where applicable, a starter embankment. Key design elements include foundation improvement (if needed), lift thickness and compaction energy, trafficability, drainage layers, and erosion control. Unsaturated conditions introduce suction-driven strength that is sensitive to moisture ingress from rainfall, capillary rise, or freeze–thaw cycles. This section summarizes the key factors to consider in the design of the filtered tailings stack.
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