95 • Wet season: During the wet season, from December to March, tailings are accumulated in the Filtered Tailings Temporary Storage Area. During this period, the face and the structural zone (corresponding to the first meters of the upper platform of the initial engineering stage) must be covered. Subsequently, during construction stage (stacking), the structural zone must remain covered. • Dry season: From April to November, tailings stacking will be carried out, with the material compacted to 98% of the MDD according to the Standard Proctor test. • Runoff: Runoff water will be conveyed toward the rear of the FTD with a maximum slope of 2%, entering the collection system and being routed to the collection pond through the bottom of the deposit. • Type of analysis: A two-dimensional (2D) transient analysis was performed, considering an analysis period of 5,475 days, equivalent to approximately 15 years. • Pore pressure activation: The pore pressure activation value for the tailings material corresponds to the upper moisture limit (15%), thus simulating the most unfavorable condition under which compacted tailings may be placed. • Saturation condition: The basal drain and filtered tailings materials exhibit unsaturated behavior at the time of their placement in the FTD. Table 3 - Constructions stages Lift DSTF Height (m) Season Rainfall time (days) Start End Nivelation 25 Wet / Dry 0 910 Lift 1 35 Wet / Dry 910 1502 Lift 2 45 Wet / Dry 1502 1980 Lift 3 55 Wet / Dry 1980 2468 Lift 4 65 Wet / Dry 2468 3089 Lift 5 75 Wet / Dry 3089 3552 Lift 6 85 Wet / Dry 3552 3915 Lift 7 95 Wet / Dry 3915 4178 Post Construction 95 Wet / Dry 4178 5475 4. RESULTS AND DISCUSSIONS The seepage analysis results indicate that, throughout the life cycle of the dam and during the construction process, a piezometric level develops within the FTD. However, the influence of considering unsaturated behavior, by implementing the soil-water characteristic curve (SWCC) as a key parameter, can be observed in Figure 7 and Figure 8, with degrees of saturation exceeding 85% in some zones. Figure 8 highlights the importance of covering the structural zone of the filtered tailings deposit during the wet season. In this case, a significant increase in saturation zones is observed during the construction stage, with degrees of saturation exceeding 85% on the downstream face of the filtered tailings deposit.
RkJQdWJsaXNoZXIy MTM0Mzk2