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1 IIUddIC�IUU -BCrq <br />3.4 Results <br />Based upon DRMS Rule 4.10.4(2), a minimum Factor -of- Safety (FS) of 1.5 is <br />required for the analyses to indicate a stable condition. <br />below. <br />The results of the analyses are included in Appendix A and are summarized <br />• Section A-A' without Coverfill Circular — minimum FS = 1.679 <br />• Section A-A' without Coverfill Block — minimum FS = 1.833 <br />• Section A-A' with Coverfill Circular — minimum FS = 1.516 <br />• Section A-A' with Coverfill Block — minimum FS = 1.571 <br />• Section B -B' without Coverfill Circular — minimum FS = 1.649 <br />• Section B -B' without Coverfill Block — minimum FS = 1.794 <br />• Section B -B' with Coverfill Circular — minimum FS = 1.599 <br />• Section B -B' with Coverfill Block — minimum FS = 1.623 <br />3.5 Discussion <br />As indicated above, the results of the analyses yielded factors -of- safety for the <br />existing slopes along gob pile #2 above 1.5. The analyses also indicate that the coverfill <br />stockpiles will not dramatically reduce the stability of gob pile 92. <br />It is important to note that the observed factors -of- safety are based upon the <br />assumptions above regarding shear strength, unit weight of coverfill, and piezometric <br />surface. In order to evaluate the impacts of changes in these parameters on the stability, <br />HBET conducted sensitivity analyses. The results of the sensitivity analyses are included <br />in Appendix B and are summarized in the following sections. <br />Unit Weighl of Covert <br />As discussed previously, the unit weight of the coverfill is likely to be less than <br />the unit weight of the in- place, consolidated native soils. HBET believes that the selected <br />value of 115 pcf is appropriate for the loosely placed coverfill. However, the sensitivity <br />analyses included increasing the unit weight of the coverfill in the model to 120 pcf. At <br />this unit weight, the factors -of- safety for both Sections A -A' and B -B' did not fall below <br />1.5. <br />Friction Angle of Gob <br />As indicated in the referenced documents, previous sensitivity analyses completed <br />by Buckhorn included friction angles (�') of 30° and 32 °. However, the triaxial shear <br />testing completed in 2005 showed fully drained friction angles of between 33.6° and <br />34.3 °. In addition, triaxial shear testing completed in October 2013 showed a drained <br />friction angle of 34.5 °. <br />X' 2008 ALL PROJECTS 01349 -Bowie Resources, LLC'01349.0001 Bowie Mine-200 - GedGob 2 Co%edill Stability' 01349.0001 R091914 doc 4 <br />