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Geotechnical Stability Exhibit <br /> Engineering Evaluation of Highwall Design for the South Quarry of the Morrison Quarry <br /> GEOLOGICAL STRENGTH INDEX SURFACE CONDITIONS <br /> FOR JOINTED ROCKS VERY I GOOD I FAIR I POOR VERY <br /> GOOD POOR <br /> STRUCTURE DECREASING SURFACE QUALITY <br /> INTACT OR MASSIVE-imact = / /0/ <br /> rock cpecimtens or masslve in fs'I 90 <br /> situ rock with few widely spaced <br /> discontinuilities <br /> n <br /> BLOCKY-well interlocked un- <br /> disturbed rock mass consistion „ 70 <br /> of cubical blocks formed by three <br /> intersecting discontinuity sets z <br /> 60 <br /> VERY BLOCKY-interlocked. x <br /> partially disturbed mass with <br /> multi-faceted angular blocks <br /> i formed by d or more joint sets �C <br /> BLOCKY/DISTURBED/SFAMY Z <br /> -folded with angular blocks <br /> formed by many intersecting <br /> discontinuity sets. Persist cna x <br /> of boding planes or schistosin <br /> i, <br /> UISINTLRATED-poorly inter- <br /> ter <br /> locked. heavily broken rock mass 70 <br /> with mixture of angular and <br /> rounded rock pieces P)Ll <br /> In / y <br /> L bockin ss due to close <br /> sp3ci k If1 <br /> of bockincss due to close spacing <br /> Of weak schistostty or shear nlanr~ <br /> l <br /> Figure 6: Geologic Strength Index for Jointed Rocks <br /> Selected Hoek-Brown parameters for stability evaluation of the existing and proposed bench <br /> configurations are summarized in Table 9 below. <br /> Table 9—Selected Hoek-Brown Design Parameters <br /> Material U sS GSI mi D <br /> Competent 10180 45 28 1 <br /> Material <br /> Talc-Gneiss 7117 35 23 1 <br /> 5.2.1.1 Design UCS Value <br /> Due to the significant heterogeneity of the rock mass in the project area, the overall average of <br /> the recent and historic UCS laboratory testing values were utilized for the competent material, <br /> with the understanding that including talc-gneiss UCS values will conservatively reduce the <br /> weight of the upper outliers (greater than 14 ksi) which are most likely caused by the abundance <br /> of very hard quartz and quartz pegmatite material within the quarry. This approach is visualized <br /> on Figure 7, wherein a scatter plot of the UCS laboratory testing results is presented and the <br /> green box indicates samples included for determination of the talc-gneiss design UCS value, <br /> and the red box encompasses samples included for determination of the competent material <br /> design UCS value. With the addition of the recent UCS testing, the recommended design <br /> May 2023 1 21 <br />