2009-03-02_PERMIT FILE - C1980004 ‎(5)‎

• Permit No: C1980004
• IBM Index Class Name: Permit File
• Doc Date: 3/2/2009
• Section_Exhibit Name: Appendix R Stability Evaluation of Proposed Gob Wastepile
• Media Type: D
• Archive: No

Table 5. Summary of Stability Evaluations
Critical Factor of SafetyZ
Cross Total Stress Effective Stress
Section' Analysis Analysis
2.87 (circular) 1.74 (circular)
Section A-A' 3.03 (block) 2.10 (block)
2.86 (circular)3 1.74 ~(circular)3
2.63 (circular) 1.74 (circular)
Section B-B' 2.76 (block) 1.~6 (block)
2.41 (circular)3 1.74 ~(~circular)3
Notes•
1. Cross section locations indicated on Drawing 3.
2. Factor of safety by Spencers procedure.
3. Considering shallow groundwater table (5-foot depth)
5.4 Sensitivity Analyses
Sensitivity analyses were conducted to evaluate the effects of variability of material properties.
The sensitivity analyses were conducted for critical total and effecijive stress analyses (i.e.,
circular failures for Cross Section B-B~. Sensitivity of six parameters was evaluated, including
unit weight of gob for total and effective stress analyses, undrained shear strength of gob (total
stress analysis), angle of internal friction (~~ of gob, and angle of internal friction of native soils
for both total and effective stress analyses. These parameters were varied plus/minus 20% of
the values indicated in Table 4 and discussed in Section 5.2. The Factor of safety was plotted
as a function of these variable unit weight and strength parameters.. These plots are presented
in Appendix D.3.
5.4.1 Total Stress Analyses
For the total stress analyses, sensitivity analyses included unit weight of gob, undrained shear
strength of gob, and internal friction angle of native silty sand. The factor of safety decreased
linearly from approximately 3.0 to 2.4 for respective gob unit weights of 72 pcf to 108 pcf.
Considering sensitivity to gob undrained shear strength (Su), the factor of safety increased
linearly from approximately 2.4 to 2.85 for respective gob undrained shear strengths of
1,060 psf to 1,590 psf. Finally, the factor of safety increased linearly with increasing native silty
sand soils from approximately 2.3 (for ~=240) to 3.0 (for ~=360).
5.4.2 Effective Stress Analyses
For the effective stress analyses, sensitivity analyses included unit weight of gob and internal
friction angle of gob and native silty sand. Neither the unit weight of gob nor the friction angle
of the native soils changed the factor of safety for the effective stress analyses.
McClave Canyon Mine stability report
Project #07-334GE0
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