2008-04-15_REVISION - M1980244 ‎(372)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 4/15/2008
• Doc Name: VOL V APP 8 Appendix C.7.1- Phase IVa Ore Slope Settlement Calculations
• From: CC&V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

E
SAC
SMITH WILLIAMS CONSULTANTS, INC.
Project: CCU Phase 5 VLF Job No. 1125
Calculation Title:
Phase Iv a Ore Slope Settlement
Prepared B : JFL Date: February 29 2008
Checked B : DTW Date: March 14 2008
In order to assess the deformation and strain along the Phase IVa ore slope and 9770 bench,
calculation points were placed within the model along the bench and the ore slope. These points
were used to monitor the stresses and strains along the Phase IVa ore slope boundary (where the
PSSA liner system will be located) and the deformation of the 9770 bench.
CONCLUSIONS:
The PLAXIS model results report is attached to this calculation sheet. In order to assess the
potential strain and deformation along the Phase IVa 9770 bench and the Phase 5 PSSA liner
system, calculation points were added to the model along the ore slope (see model output). Total
displacements are used to determine the settlement of the Phase 5 PSSA bench under future loading
conditions. In the Phase 5 design, the PSSA bench will be raised above the 9770 elevation to
counter settlement due to ore loading. And to maintain the minimum 5 ft freeboard within the Phase
5 PSSA. The total displacements can also be used to estimate extension of pipelines and electrical
cables placed on the 9770 bench. Shear strains are used to assess movement along the Phase IVa ore
slope that may impact the PSSA liner system. Shear strains reflect extension of the geomembrane
liner by settlement (in two dimensions).
Data from the model and the calculation points show that after the VLF is loaded to 590 feet with
ore, the global strain on the Phase 5 PSSA liner system is approximately 2.5 %, which is acceptable
for the VLF liner systems. The shear strain plots for the Phase IVa ore slope (which form the Phase
5 PSSA) are presented in Figure 3.
Based on the model output, the 9770 bench is anticipated to settle approximately 5 feet due to the
590 ft ore loading. Therefore, the PSSA bench along the Phase IVa ore slope should be set at an
elevation of 9775 feet in order to preserve the minimum freeboard within the PSSA.
For potential buried pipelines and powerlines located along the 9770 bench, the linear strain that
could develop from ore settlement can be estimated by considering simple elongation. The length of
the 9770 bench is approximately 2,800 feet. Assuming the settlement occurs at the middle (e.g.
1,400 ft); the tensile strain (elongation) by settlement is less than 1%.
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