PERMFILE47216

• Permit No: C1981034
• IBM Index Class Name: Permit File
• Doc Date: 3/19/1984
• Section_Exhibit Name: APPENDIX G Rocky Mtn Geotechnical - Red Canyon #2 Portal Cut Investigation 3/84
• Media Type: D
• Archive: No

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5.0 STABILITY ANALYSIS
5.1 DES.ISI1 PARAMETERS
The design parameters for the slope stability analysis were based
on both previous laboratory testing on the various rock materials
in Rocky Mountain Geotechnical's report dated August 25, 1981 and
November 3, 1981, and from previous experience with the types of
soils encountered at this particular site.
The strength parameters for the rock materials were based on the
unconfined compressive strengths summarized in the Rocky Mountain
Geotechnical November 3, 1981 report. These unconfined
compressive strengths, as summarized on Table 1.0, were then used
to develop shear strength parameters to be used in the slope
stability analysis by utilizing a method described in
"Underground Excavations in Rock" by E. Hoek and E.T. Brown.
This method utilizes approximate equations for principal stress
relationships and Mohr Envelopes for intact rock and joint rock
masses based on extensive laboratory testing. In order to use
these equations, the rock masses were first classified based on
data obtained during the field reconnaissance trip and from the
previous soil boring program. A Classification of Intact Rock
Strength (CSIR) rating was developed for each individual rock
mass. A shear stress equation from which the rock's friction
angle and cohesion intercept could be determined was established
for the given type of rock mass by knowning its CSIR rating and
its unconfined compressive strength. These values, as summarized
in Table 1, were then utilized in the slope stability analysis.
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