2010-05-12_PERMIT FILE - C1981010

• Permit No: C1981010
• IBM Index Class Name: Permit File
• Doc Date: 5/12/2010
• Doc Name: Revised K-Pit Butttress Fill Stability Analysis, Feb 2010
• Section_Exhibit Name: Appendix T
• Media Type: D
• Archive: No

February 1, 2010
Page 6
• Figure 8 shows the pre - mining conditions with an existing FOS= 0.725.
• Figure 9 shows KIL -3 and K1 L -4 excavated to the top of the I -Scam, FOS increased to
1.1.83.
• Figure 1.0 shows conditions during the mining of the K1.Q -3 block to the R -Scam, the
minimum FOS remains 1.183.
•
Figure 11 shows the conditions once the K1 L -13, KIL -14 and KI.L -15 blocks are mined
to the K -seam, the FOS increases to 1.855.
The cut sequence as developed by TMI is a suitable mining plan when the localized areas
of surface instability are addressed. AAI recommends that these locally steep slopes be reduced
prior to performing any mining activity within 500 feet (ft) down slope of the area of concern.
The reduction of slopes should be accomplished by excavation of material rather than simply
pushing the material. down. the slope.
3.2 Revised .K -Pit Buttress Analysis
As with the K -Pit mining models, the filtering of near- surface failure plains led to some
confusion as to the need for and the location of the K -Pit buttress. When the model forces the
failure plain to be deep seated, and the surface north of the buttress is not allowed to fail, the
buttress solves the problem. However, the current actual. conditions in the K -Pit area are largely
dictated by the behavior of the materials adjacent to the I -Seam. AAI identified these materials
to be the failure surface of the haul road slide of 2008. The presence of I -Seam below or
adjacent to increased Loading, or change in moisture content, can result in uncontrolled ground
movement.
The material properties used for the K -Pit mining models were previously estimated
properties that would represent residual shear - strength characteristics. The materials north of the
G- Strike -Pit were not subject to the deformation of the G -Pit slide; therefore, formation material
properties were adjusted to represent virgin ground. Rocscience's "RocLab" computer program
(Rocscience 2009) was used to estimate properties of intact material for the I -Scam group and
the K -Seam group. Table 2 shows the upgraded values for the formational material.
Table 2. Revised Geotechnical Properties of Materials in
K -Pit and Toe Buttress Models
The slope stability for the revised K -Pit buttress was analyzed using S.LOPE/W software.
No artificial constraints were imposed, and the resulting FOS was 0.755. The height of the fill
Agapito Associates, Inc.
Rock Mechanics Properties
Dry
Friction
Stratum
Density
Cohesion
Angle
(pct)
(kst)
( degrees)
I -Seam materials (disturbed)
126.3
0.5
3.8
I -Seam materials (undisturbed)
126.3
0.7
6.3
K -Seam materials (disturbed)
137.3
0.5
15.2
K -Seam materials (undisturbed)
137.3
3.6
23.5
The slope stability for the revised K -Pit buttress was analyzed using S.LOPE/W software.
No artificial constraints were imposed, and the resulting FOS was 0.755. The height of the fill
Agapito Associates, Inc.