1255 • Freeze–thaw processes: Repeated freeze–thaw cycles can gradually alter pore structure, permeability and strength, especially in fine-grained or partially saturated materials. Laboratory and field studies have shown that freezing can cause redistribution of moisture and development of microcracks, while thawing may lead to softening and increased deformation under load. The net effect on stability depends on material properties, moisture history, compaction level and drainage conditions, highlighting the need for longterm monitoring and modeling of freeze–thaw behavior. • Dust and erosion control: Dry materials are susceptible to wind erosion and dust generation, which can have environmental and occupational health impacts. In exposed northern environments, wind speeds and the lack of vegetation may exacerbate dust issues, requiring surface treatments, temporary covers or progressive reclamation to protect tailings surfaces. Erosion by wind and water can also affect local slope stability and drainage patterns if not managed appropriately. Operational experience suggests that maintaining stability under these conditions requires combining robust initial design with adaptive management. This includes flexible deposition plans, continuous surveillance (for example using drones and remote sensing), and the capacity to modify drainage, compaction and cover strategies as more is learned about site-specific behavior over time. 4. LIMITATIONS AND CLIMATE-RELATED RISKS While dry stacking offers clear advantages in terms of water recovery and reduced reliance on large slurry impoundments, its application in Arctic and sub-Arctic environments is constrained by several limitations and climate-related risks. These arise from the coupling between tailings behavior, weather variability and long-term climate trends, and from the current lack of comprehensive operational datasets under northern conditions (Tuomela, 2022; Sahu et al., 2020). 4.1 Operational limitations in cold climates Cold temperatures and harsh winter conditions can reduce the performance and reliability of filtration and deposition systems. Filtration rates may decrease at low temperatures due to changes in slurry rheology and water viscosity (Davies & Rice, 2001), potentially leading to higher residual moisture contents and difficulties in consistently achieving the target moisture window. Snowfall, ice formation on equipment and limited daylight can further restrict operating windows and complicate logistics during winter months. On the stack, frozen surfaces may temporarily improve trafficability, but thaw periods can rapidly reduce bearing capacity and lead to rutting, local instability or delays in placement and compaction. Short construction seasons in Arctic regions, combined with long periods of frozen ground, demand careful scheduling and the capacity to adapt deposition plans to year-to-year variability in weather conditions. 4.2 Freeze–thaw cycles and long-term behavior Repeated freeze–thaw cycles represent a central challenge for the long-term performance of drystacked tailings. Experimental studies and cold-climate geotechnical research indicate that freeze–thaw can modify density, pore structure and hydraulic conductivity, with potential implications for strength, settlement and seepage. Fine-grained or partially saturated materials are particularly sensitive to these processes, which may gradually reduce strength or create preferential flow paths over time (Andersland & Ladanyi, 2004). In addition, the interaction between tailings and foundation materials under freeze–thaw conditions must be considered. Frost heave and differential thaw settlement in the subgrade can induce deformations and stresses in the stacked tailings and drainage systems, potentially affecting both global stability and leakage pathways (GTK, 2021; Tuomela, 2022). These processes are influenced by local climate, snow cover, drainage conditions and thermal properties of the materials, and they evolve over decades, making them
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