1020 3.1 Geotechnical Characterization The first step in achieving this objective was the development of the geotechnical (hydraulic) characterization. In this stage, the parameters required for the seepage analysis were defined, including saturated permeability, permeability ratio, degree of saturation, specific gravity, void ratio, and moisture content. Many of these initial parameters are essential, as they are used to calculate the saturated volumetric or gravimetric water content. Table 17 – Material Properties of filtered tailings deposit Properties Symbol Units Saturated tailing Unsaturated tailing Drain Unit weight y kN/m3 22.7 21.10 18.68 Moisture content w % 21.2 15.0 12.0 Initial void ratio e0 - 0.66 0.66 0.59 Specific gravity Gs - 3.10 3.10 2.70 Degree of saturation S % 100.0 70.7 55.1 Saturated Permeability k m/s Figure 5 1E-4 Permeability ratio Ky/Kx - 0.1 0.1 1 In adittion, the SWCC parameters for the transient analysis were selected to represent unsaturated behavior. These parameters are presented in Table 18, where the saturated permeability and the unsaturated parameters depend on depth (vertical stress). The variation of the parameters of the Soil-Water Characteristic Curves (SWCC) is due to changes in the volumetric water content. The saturated volumetric water content depends on the void ratio, which varies as a function of vertical stress (depth). The Soil-Water Characteristic Curves (SWCCs) are shown in Figure 74. Table 18 - Fredlund parameters (unsaturated tailings) Depth a (kPa) n m θsat Ksat (m/s) Ky/Kx 0 – 5 1 250 1.4 0.6 0.3976 4.8E-10 0.1 5 – 10 1 500 1.4 0.6 0.3779 7.4E-11 0.1 10 – 20 1 750 1.4 0.6 0.3696 3.1E-11 0.1 20 – 30 1 950 1.4 0.6 0.3575 8.6E-12 0.1 30 – 50 2 175 1.4 0.6 0.3450 2.5E-12 0.1 50 – 70 2 300 1.4 0.6 0.3301 1.0E-12 0.1
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