2009-09-21_REPORT - C1981010

• Permit No: C1981010
• IBM Index Class Name: Report
• Doc Date: 9/21/2009
• Doc Name: Horse Gulch Fill Stability Analysis, May 2009
• Permit Index Doc Type: Waste Pile/Fill Report
• Section_Exhibit Name: Appendix T
• Media Type: D
• Archive: No

May 29, 2009
LIST OF TABLES
Page ii
Page
Table 1. 2008 Auger Drilling Data ........................................................................................... 2
Table 2. Direct Shear Test Results ............................................................................................ 3
Table 3. K-Pit Buttress Drill-Hole Data .................................................................................... 5
Table 4. Engineering Properties of Generic Spoil Types .......................................................... 6
Table 5. Material Properties for Computer Modeling ............................................................... 7
Table 6. Horse Gulch Fill Characteristics ................................................................................. 7
Table 7. Material Properties and Factors of Safety by Material Type ...................................... 9
LIST OF FIGURES
Page
Figure 1. Aerial Photo of Horse Gulch with Proposed Fill Contours and Drill-Hole
Locations .....................................................................................................................2
Figure 2. Base Model Geometry ................................................................................................3
Figure 3. SPT Blow Count versus Bedrock Contact ..................................................................4
Figure 4. Aerial Photo of K-Pit Buttress with Proposed Fill Contours and Drill-Hole
Locations ............................................................................................................ .........5
Figure 5. Natural Segregation of Coarse Rock at Toe of Dragline Spoil Pile, G-Dip Pit. ......... 7
Figure 6. Location of Slope-W Analysis Section .............................................................. .........8
Figure 7. Typical Output from Slope-W ........................................................................... .........8
Figure 8. Topsoil Condition during Spring Thaw ............................................................. .......10
Figure 9. Relatively Dry Conditions of the Materials below the Topsoil ......................... .......10
Figure 10. No Expression of Near-Surface Water Fall 2008 .............................................. .......11
Figure 11. Isometric View of Failure Block, Velocities Case 1, Factor of Safety 1.87 ...... .......12
Figure 12. Sectional View of Failure Block, Velocities Case 1, Factor of Safety 1.87 ...... .......12
Figure 13. Sectional View of Failure Surface, Shear Strain Case 1, Factor of Safety 1.87 .......13
Figure 14. Isometric View of Failure Block, Velocities Case 2, Factor of Safety 1.79 ...... .......13
Figure 15. Sectional View of Failure Block, Velocities Case 2, Factor of Safety 1.79 ...... .......14
Figure 16. Sectional View of Failure Surface, Shear Strain Case 2, Factor of Safety 1.79 .......14
Figure 17. Isometric View of Failure Block, Velocities Case 3, Factor of Safety 1.51 ...... .......15
Figure 18. Sectional View of Failure Block, Velocities Case 3, Factor of Safety 1.51 ...... .......15
Figure 19. Sectional View of Failure Surface, Shear Strain Case 3, Factor of Safety 1.51 .......16
Figure 20. Sectional View of Failure Surface, Cases 1 through 3 ...................................... .......17
Figure 21. Rocky Nature of K-Ridge Overburden .............................................................. .......19
Figure 22. Stockpiled Underdrain Material ......................................................................... .......19
Figure 23. Natural Segregation of Coarse Durable Rock at Toe of G-Dip Pit Dragline
Spoil Pile ............................................................................................................ .......20
Figure 24. Schematic Drawing of Proposed Underdrain .................................................... .......21
Figure 25. Plan View of Initial Underdrain Location ......................................................... .......22
Figure 26. Dragline Casting Schematic with Underdrain Location .................................... .......22
Figure 27. K-Pit Nomenclature ........................................................................................... .......23
Figure 28. K-Ridge Dragline Stripping Limits ................................................................... .......24
Figure 29. B-Block Spoils Movement ................................................................................. .......25
Agapito Associates, Inc.