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Cripple Creek & Victor Gold Mine <br />Valley Leach Facility Expansions <br />Detailed Design for Permitting <br />NewFields Project No. 475.0106.064 <br />September 2025 <br /> <br /> <br /> <br />Page 18 <br />5.1.2. Design Ground Motions <br />To assess the stability of slopes during seismic loading, a pseudostatic approach was used where <br />the potential slide mass is subjected to an additional, destabilizing horizontal force which <br />represents the effect of earthquake motions and is directly related to the PGA. The seismic force <br />is the weight of the slide mass multiplied by a horizontal pseudostatic earthquake coefficient (kH), <br />which is commonly related to the peak ground acceleration by an acceleration multiplier. <br />Referenced values of the acceleration multiplier range from approximately 0.2 to 0.8, with 0.5 <br />being a commonly applied value (Duncan and Wright, 2005). <br />For the current evaluation, the simplified methodology proposed by Bray and Macedo (2019) was <br />used to estimate the kH value based on 6-inches of allowable deformation, the design earthquake <br />magnitude for the 1 in 2,475 years Annual Exceedance Probability event, and the natural <br />frequency of the failure mass. The estimated kH value is a function of presumptive shear wave <br />velocity through the ore and embankment fill and use of either the mean or modal earthquake <br />magnitude. The methodology resulted in a kH value less than half the PGA, and for the current <br />analysis a kH value of half the PGA (0.07g) was conservatively applied. <br />5.1.3. Material Properties <br />The material properties used in the stability analysis are based on available laboratory test data <br />and our understanding of general site conditions. The materials are summarized in Table 5.1 and <br />discussed below. <br />Table 5.1 –Stability Evaluation Material Properties <br />Material <br />Moist Unit <br />Weight <br />(psf) <br />Power Curve Mohr – Coulomb <br />π‰ΰ΅Œπ‘¨βˆ™πˆπ’π‘© π‰ΰ΅Œπ’„α‡± ΰ΅… πˆπ’π­πšπ§π‹β€² <br />A B ’ <br />(deg) <br />c’ <br />(psf) <br />Ore (Existing and Proposed) 120 3.963 0.841 - - <br />Composite Liner Interface 120 1.169 0.886 - - <br />Pit Backfill and Fill 120 35 0 <br />Foundation (Sand and Gravel) 125 - - 32 0 <br />Foundation (Bedrock) 150 - - 45 0 <br /> <br />Ore: Direct shear tests were completed on different mixtures or virgin ore materials and failure <br />was chosen at 15 percent strain (NewFields, 2019, 2023). A non-linear power curve was <br />considered the most representative failure envelope and plots slightly higher at low stress and <br />slightly lower at high stress compared to average rockfill characteristics as shown on Figure 5.1.