2007-05-15_GENERAL DOCUMENTS - M1980244

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Subject Cripple Creek and Victor Made by DLG Job No 063-2216 Gold Mining Co. Ore Loading Near Uncertified Liner Checked by Date 2/9/2007 Isolation Fla 4SOCia*S Global Stability Analysis Approved by Sheet No 1 of 2 OBJECTIVE: • Determine allowable slope angles and slope heights for ore stacking in the vicinity of the proposed uncertified liner isolation flap. The flap will be located near the existing Load Out Bin (LOB) at the Cripple Creek and Victor Gold Mining Co. (CC&V) facility near Victor, Colorado. GIVEN: • As-built liner grades (Provided by CC&V, February 2007) • Current topography (Provided by CC&V, February 2007) • Geotechnical parameters from previous work (Golder, 2000) • Location of the proposed uncertified liner isolation flap (Golder Associates, Inc.) • The minimum acceptable static factor of safety for the overall ore slope is 1.3 (Golder, 2000). ASSUMPTIONS: • The water table is assumed to be deep enough such that it will not adversely affect stability. • Per the design criteria, the maximum hydraulic head on the liner is 2 feet (Golder, 2000). Two feet of solution was incorporated into the analyses. • The strength parameters used for this analysis are from Golder 2000, summarized below: Dry Unit Friction Cohesion Material Weight Angle (deg) (psf) c Foundation Soil 120 26 0 Soil/Liner Interface 120 18 0 Ore 110 40 770771 ANAYLSES: • Primary stability analyses were performed using a Golder spreadsheet that evaluates an active/passive wedge failure method. This method assumes a 2 block active/passive wedge failure, with the failure surface starting at the crest of the ore, extending down to the liner, and then progressing along the soil/liner interface to the toe of the slope. The method was implemented with an EXCEL spreadsheet, using the SOLVER.XLA add-in to automate the search for the critical failure surface. • The results of the wedge-failure analyses were checked using RocScience's limit equilibrium program SLIDE 5.028. Block failure surfaces were most critical. Minimum factor of safety was determined using the program's search algorithm and calculations based on Spencer's method. • Calculations were performed to determine the height and slope angle to meet the stability requirements for the overall ore heap. • Stability analyses were performed on several cross-sections cut through the ore at various locations and various orientations. There were two critical design sections: - A section cut parallel to the direction of maximum ore slope, perpendicular to the liner flap. - A section cut at a 40 degree angle to the direction of maximum ore slope, where the apparent slope of the ore decreases and the apparent slope of the liner at the base increases. The apparent angle of a slope can be calculated using the following equation: JA0001ISC063.2216 CC&Y. LOBWI.CIFLAP PROJCCTICLOBAL STABIUMDOC