2014-08-19_PERMIT FILE - C1980007 ‎(10)‎

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 8/19/2014
• Doc Name: Haul Road Geotechnical Design Method
• Section_Exhibit Name: Exhibit 82 Appendix H
• Media Type: D
• Archive: No

slopes. The program is capable of using a variety of methods to compute the factor of safety of a
slope while analyzing complex geometry, stratigraphy, and loading conditions.
Spencer's method was used as the search technique to determine the factor of safety of the slopes in
this stability analysis. This method is considered the most adequate because it satisfies all conditions
of static equilibrium and provides a factor of safety based on both force and moment equilibrium.
Stability of a slope is often reported using a factor of safety value. The factor of safety is the ratio of
the summation of forces and moments that are resisting slope movement to the summation of
forces and moments that cause slope movement.
The entry and exit method was used to determine where along the ground surface the potential failure
surface would enter and exit. An initial trial was performed using engineering judgment and a range
of failure surface entry and exit locations along the modeled slope to determine the optimal extents.
2.4.3 Geometry
A cross-section through the East Slide was used for the seepage and stability analysis. This cross-
section is shown on Figure 5. The granular drainage blanket and the layer of carbonaceous shale at
the top of the bedrock bench were both included in the model.
2.4.2 Results
The results of the seepage and limit equilibrium stability modeling for the as -built repaired slope are
included in the following sections.
2.4.2.1 Seepage Analysis
Figure 7 shows the total head contours computed by SEEP/W for the as -built repaired slope. It can be
seen that the phreatic surface (dashed blue line) has been drawn down by the presence of the drainage
blanket under the HR -1 haul road and the pipe at the bottom of the upslope interceptor trench.
2.4.2.2 Stability Analysis
Table 4 shows the results of the stability modeling for the haul road slide repair.
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