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2017-06-09_REVISION - M1980244
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2017-06-09_REVISION - M1980244
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Entry Properties
Last modified
12/26/2020 8:55:30 AM
Creation date
6/13/2017 8:02:30 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1980244
IBM Index Class Name
REVISION
Doc Date
6/9/2017
Doc Name
Adequacy Review Response #2
From
CC&V
To
DRMS
Type & Sequence
TR89
Email Name
TC1
Media Type
D
Archive
No
Tags
DRMS Re-OCR
Description:
Signifies Re-OCR Process Performed
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Technical Memorandum ■ <br /> Cripple Creek&Victor Gold Mine ■ <br /> SGVLF Stability Evaluation—Nonagglomerated Tailings <br /> NewFields Job No.475.0106.009 <br /> 1 June 2017 <br /> showed that the ore mixed with nonagglomerated tailings exhibited a slightly reduced friction <br /> angle than the virgin ore samples, but no significant reduction in shear strength was noted. <br /> 3.0 STABILITY ANALYSES <br /> Stability analyses were performed along the most critical sections of SGVLF in order to <br /> determine the limiting shear strength of the ore before unacceptable factors of safety were <br /> achieved. The stability analyses were implemented as a parametric study to identify the <br /> necessary shear strength (friction angle) required to achieve the minimum required factor of <br /> safety. <br /> The stability analyses were performed using the computer program SLIDE 7 developed by <br /> Rocscience (2016). SLIDE is a two-dimensional slope stability program for evaluating circular or <br /> noncircular failure surfaces in soil or rock slopes using limit equilibrium methods. Spencer's <br /> method of slices was utilized within the stability model and assumes all interslice forces are <br /> parallel and have the same inclination. The factor of safety can be defined generally as the <br /> resisting forces along a potential failure plane divided by the gravitational and dynamic driving <br /> forces, therefore factors of safety in excess of unity indicate stability and those less than unity <br /> indicate instability. Both static and seismic conditions were analyzed. <br /> Minimum acceptable factors of safety for static and pseudostatic conditions were established <br /> as 1.3 and 1.15, respectively, based on Colorado Division of Reclamation Mining and Safety <br /> (DRMS) guidelines and the facility being designated a "critical structure" as slope failures could <br /> impact the adjacent highway and/or have significant environmental impacts. <br /> 3.1 Design Ground Motions <br /> To assess the stability of slopes during seismic loadings, a pseudostatic approach was utilized in <br /> which the potential sliding mass is subjected to an additional, destabilizing horizontal force that <br /> represents the effects of earthquake motions and is related to the peak ground acceleration <br /> (PGA). The seismic force is the weight of the sliding mass multiplied by a horizontal pseudo- <br /> static earthquake coefficient (kh). <br /> The kh is typically considered as a portion of the PGA because during an actual earthquake the <br /> acceleration within the potential sliding mass is cyclic and varies over the duration of the <br /> earthquake and the direction of the acceleration changes throughout the seismic event. <br /> Therefore, an average horizontal coefficient is assigned that is typically less than the PGA <br /> experienced at the base of the structure. Hynes-Griffin and Franklin (1984) discussed that use <br /> of one-half of the PGA for the horizontal pseudostatic earthquake coefficient will result in slope <br /> deformations that will be within tolerable limits. This reduction in the pseudostatic seismic <br /> coefficient is typically coupled to a 20 percent strength reduction for materials that are <br /> Page 4 <br />
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