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• WHEXSIopeEvaluation AdrianBrown <br />WILD HORSE EXTENSION SLOPE DESIGN SUMMARY <br />1. The slopes of the proposed Wild Horse Extension mine have been evaluated and designed. <br />2. A total of 12 geotechnical holes were drilled, logged, and tested to obtain information for the <br />design of the WHEX slopes. <br />3. The rocks materials in the WHEX mine will be granite, schist, and gneiss on the eastern wall, <br />and volcanic phonolite and breccia on the western and northern walls. <br />4. The intact rock strength of the wall rocks aze high, with unconfined compressive strengths <br />averaging in excess of 10,000 psi. <br />5. The WHEX mine area is chazacterized by adverse structure: <br />a. Foliation in the granitic rocks dips into the mine at angles from 30° to 70° <br />b. Joint sets in the volcanic rock dip into the mine at angles from 20° to 60° <br />• <br />6. Discontinuities in the rockmass aze in general strong, with friction angles in excess of 40°. <br />7. Design slope angles aze mainly controlled by potential failure along in-dipping structures. <br />8. The design uses single benches with 35 foot vertical spacing and vertical interbench slopes. <br />9. The construction details for the mine walls are as follows: <br />Wall North- <br />east South- <br />east West &~ <br />North <br />Predominant Rock Material Granite Granite Volcanic <br />Overall angle degrees 45 50 60 <br />Berm width feet 35 30 20 <br />Inter bench angle degrees 90 90 90 <br />Bench height feet 35 35 35 <br />10. Slope excavation at WHEX will require special attention to blasting practices: <br />a. Trim blasting using close-spaced holes. <br />b. Depth control on bench blast holes. <br />c. Location control to avoid blasting on the future crest. <br />• <br />Report 1385L.200309017 ~ <br />