2008-04-15_REVISION - M1980244 ‎(197)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 4/15/2008
• Doc Name: VOL IV APP 5 Attachment 3 Wildhorse Extension Mine Slope Design
• From: CC & V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

• WHEXSIopeEvaluation Adrian6rown
Table 8. Summary of Slope Design Results
Core Hole Wall
Se ment Wall
Hei ht Wall
Material Water
Pressure Effective Stress
Rockmass Stable
An le
(feet) Friction
de Cohesion
si Circular
de Wedge
de
GT03-01 NNE 455 Granitic Sli ht 23 204 >60 45
GT03-02 NE 455 Granitic Sli ht 24 174 >60 45
GT03-03 NE 455 Granitic D 30 246 >60 50
GC02-235 NE 455 Granitic D 50
GT03-04 E 560 Granitic D 30 290 >60 50.
GT03-05 ESE 455 Granitic D 23 217 >60 50
GT03-06 SE 280 Volcanic D 37 420 >60 n/a
WHC02-32 S 550 Granitic D 37 362 >60 45
GT03-08 N 385 Volcanic D 38 435 >60 n/a
GR-443 SW 460 Volcanic D 39 493 >60 n/a
GR-477 NW 410 Volcanic Wet 37 435 >60 n/a
6.4.1 Northeast
The northeast wall of the mine has been investigated with four drill holes: GT03-O1, GT03-02, GT03-03,
• and GC02-235. All are similar in both the results that they give, and the information relevant to mine
wall stability. The findings can be summarized as follows:
1. Mine Wall Material. Altered gneiss, schist, and granite. Weathering is limited, with the oxidized
zone extending down to about 400 feet, close to the proposed depth of the mine in this area.
Intact rock strength is good, averaging approximately 5,000 psi. The northeast wall of the mine is
located in ore-grade material (part of the Grassy Valley orebody), and is expected to be more
altered and disturbed than material on the east wall further south.
2. Rock Quality. Good, reducing with depth due to reducing intact rock strength and increasing
fracture frequency. Some fractures and faults aze infilled with clayey materials, and some display
slickensides.
3. Structure. Generally adverse. Foliation of gneiss and schist rocks in the slope dips into the mine
at angles ranging from 30 to 70 degrees. Fracturing in the rock also generally dips adversely into
the mine, although it is not expected that these features are extensive. Extensive fractures and
faults are expected to be sub-vertical, and not a stability issue.
4. Water. Water is present in the rock, generally at low pressure in the order of 10% of hydrostatic.
The mine is expected to drain, but water pressure is expected to somewhat reduce slope
performance.
Based on the evaluations presented in Attachment B for the four holes in this area, the recommended
slope angle for this portion of the wall is 45 degrees, controlled by the potential for large-scale sliding
• (wedge) failure along foliation or in-dipping extensive fracture planes. If it transpires that the foliation
Report 1385L.200309017 14