939 increasingly internalize water scarcity, climate resilience, and long-term risk, filtered tailings are poised to become not just a technical option but a strategic imperative. 7. CO-DISPOSAL & INTEGRATED WASTE STRATEGIES As the mining industry seeks tailings solutions that reduce environmental risk, lower long-term costs, and improve landform stability, co-disposal and integrated waste strategies have emerged as promising alternatives or complements to conventional tailings storage. These strategies leverage the contrasting physical and hydraulic properties of tailings and waste rock to create engineered deposits with enhanced geotechnical performance, reduced acid rock drainage (ARD) potential, and more efficient land use. Although filtered tailings are not a prerequisite for all forms of co-disposal, they significantly enhance blendability, compaction, and deposit stability, making them central to many of the most successful co-disposal concepts. 7.1 Rationale for Integrated Waste Strategies Traditional mining waste management separates tailings and waste rock into different facilities. However, this approach presents well-documented challenges: • Tailings are fine-grained, low-shear-strength materials with good water retention but poor structural stability. • Waste rock, by contrast, is highly permeable, prone to oxygen ingress, and susceptible to ARD, especially when sulphide-rich. Blending these two waste streams can result in engineered materials that combine the strengths of each: high shear strength from waste rock and low hydraulic conductivity from tailings. Laboratory tests across multiple mix ratios show significantly improved material gradation, lower permeability, and reduced oxygen ingress, which help control ARD. • The resulting “co-mixed” material therefore offers: • enhanced physical stability, • reduced geochemical risk, • the potential for smaller or integrated landforms, and • simplified closure pathways. 7.2 Filtered Tailings as an Enabler of Co-Disposal Filtered tailings play a crucial role in modern co-disposal strategies. Their low moisture content and controlled grain size distribution provide a stable fine fraction that mixes well with coarse materials. 7.2.1 Moisture Control And Blendability The (Palmer et al.) study establishes a strong relationship between cake moisture content and blendability, identifying an optimal moisture level near 95% of Proctor optimum (~16% moisture). At this condition: • the tailings cake fragments less, • maintains cohesiveness, • mixes more uniformly with aggregates, and • yields more stable co-disposal mixtures.
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