1258 • Robust material characterization and moisture window definition. Early-stage testing should quantify how particle size distribution, mineralogy and fines content affect moisture–density relationships, frost susceptibility and trafficability. This supports defining a realistic target moisture window and compaction specification that can be maintained under variable operating conditions. • Layered construction with conservative geometries. Lift thickness, slope angles and benching arrangements should be selected to ensure both global stability and effective runoff control under extreme melt and rainfall events. Designs should be checked against multiple climate scenarios and updated as new information becomes available. • Integrated water and drainage management. Surface and internal drainage systems need to be dimensioned for a range of snowmelt and storm events, including those projected under future climate scenarios. Provision for adaptive measures such as additional drains, diversion channels or temporary storage should be included in the initial layout. • Thermal and freeze–thaw considerations. Thermal analyses should be incorporated into design, particularly where permafrost or ice-rich foundations are present. This includes assessing expected changes in active layer thickness, potential frost heave and thaw settlement, and their implications for long-term deformations and seepage pathways (Andersland & Ladanyi, 2004; GTK, 2021). • Monitoring-enabled adaptive management. Instrumentation and monitoring plans must be an integral part of design, not an afterthought. Piezometers, temperature sensors, surface displacement measurements, remote sensing and visual inspections provide the feedback needed to adapt deposition, drainage and cover strategies over the lifetime of the facility. 6.2 Research gaps and priority needs Based on current practice and ongoing research in northern dry stacking, several high-priority knowledge gaps can be identified: 1. Long-term freeze–thaw effects on filtered tailings. Repeated freeze–thaw cycles over decades are expected to modify the microstructure, hydraulic conductivity and strength of filtered tailings, yet these effects remain poorly quantified for different mineralogies, fines contents and moisture histories. 2. Coupled thermo–hydro–mechanical (THM) modeling and validation. Existing THM models still face limitations in capturing the combined effects of freezing, thawing, variable saturation and mechanical loading in tailings and foundation materials, and their calibration is constrained by the scarcity of long-term monitoring data. 3. Impact of changing climate extremes. The consequences of more frequent rain-on-snow events, higher intensity storms and evolving snowpack dynamics on run-off, infiltration and pore pressure development in dry stacks are not yet fully understood, particularly under different climate scenarios and design configurations. 4. Permafrost degradation and foundation response. In permafrost regions, the effects of thawing ice-rich layers and changes in ground thermal regime on bearing capacity, settlement and leakage risks for dry-stacked facilities remain a major source of uncertainty over the full life cycle of a mine.
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