2008-04-15_REVISION - M1980244 ‎(256)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 4/15/2008
• Doc Name: VOL V APP 8 Valley Leach Facility Phase 5 Extension Design
• From: CC & V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

S Z
SMITH WILLIAMS CONSULTANTS, INC.
normal stress) and 36 degrees (under high normal stress) in the stress range expected along
critical stability failure surfaces in the VLF. Weighting the internal friction angle to the normal
stress levels expected along critical failure surfaces results in an internal friction angle of 38 to
40 degrees. The test results are presented in Appendix B. Shear tests were also conducted in
nominal 3/-inch ore materials. The test results from the 3/-inch ore resulted in an internal angle
of friction of 39 degrees, which is similar to the 1'h-inch ore test results. These shear test results
indicate that an angle of internal friction between 38 to 40 degrees can be used for ore that is
nominally sized between. l %2 and 3/ inches. 'These test results are within the range of published
shear strength data for rock fill materials (Ceps 1970), where the internal friction angles range
between 39 to 50 degrees for similar sized materials under similar normal stresses. Based on the
results of the shear tests conducted on the Cresson ore and published data, an internal friction
angle of 40 degrees is suitable for the stability analyses. The in-place net density of the material
is modeled at 110 pcf, which is consistent with that submitted previously to the DRMS.
Composite Liner. The composite liner used in the stability model is represented by one of the
following configurations depending upon the location within the VLF:
1. Phase I: A 1-foot-thick layer of Ironclad SLF overlain by an 80-mil smooth VLDPE
geomembrane liner, representing the material used as the composite liner for Phase I.
Interface direct shear testing was performed by GeoSyntec Consultants of Atlanta,
Georgia using four different normal stress values ranging between 50 and 300 psi
imposed on a sec"tion of Ironclad SLF overlain by 80-mil smooth VLDPE
geomembrane overlain in turn by DCF material. The interface testing for these
normal loads were used to define a linear relationship (friction angle and cohesion)
between the normal loads calculated in the stability section slices, and the
corresponding shear strength. The Ironclad SLF was compacted to 95 percent of the
standard Proctor maximum dry density and near the optimum moisture content. Test
results were presented to the DBMS in Amendment No. 6 (CC&V 1993) as part of
Golder's October 1993 report titled "Permitting Level Design Evaluation of the
Expansion of the Mining and Ore Processing Facilities:.Cresson Project." A copy of
the interface shear strength results is presented in Appendix B of this report.
Additional testing on this liner configuration was completed, as part of Amendment
No. 8, to a normal stress value of -500 psi. The test results are presented in Appendix
B. The results of the interface shear testing indicate a residual angle of internal
friction of 28 degrees and a cohesion of 1,635 psf, the composite liner was modeled
• as having an angle of internal friction of 24 degrees and 100-psf cohesion.
S:\PROJECTS\1125 CCSV PHASE 5 VLF\H2 - DESIGNWREQUA VLFIVLF PHASE 5 FINAL REPORT V2.DOC 31