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2009-10-16_PERMIT FILE - M2009082 (27)
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2009-10-16_PERMIT FILE - M2009082 (27)
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Last modified
8/24/2016 3:56:14 PM
Creation date
10/20/2009 9:21:12 AM
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Template:
DRMS Permit Index
Permit No
M2009082
IBM Index Class Name
PERMIT FILE
Doc Date
10/16/2009
Doc Name
Stability Analysis
From
Lafarge West, Inc.
To
DRMS
Media Type
D
Archive
No
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DRMS Analysis, Highwall Setback to Property Line <br />The Division of Reclamation Mining and Safety (DRMS) requires that gravel pit highwalls within 200 <br />feet of significant manmade permanent structures (such as utilities) be investigated for slope stability. <br />Furthermore, the DRMS requires that the gravel mine highwalls be modeled as vertical unless it can be <br />demonstrated that the slope angle of the highwall will be controlled during mining. Additionally, the <br />DRMS requires that the analysis be performed using the DRMS parameters for sites where laboratory <br />testing is absent. These parameters are given below on Table 2: <br />Table 2: DRMS Model Parameters <br /> <br />Soil Type Effective <br />Friction Angle <br />(de rees) Effective <br />Cohesion <br />c' (psl) Saturated Unit <br />Weight <br />sir ( c <br />Overburden 28 50 114 <br />Gravel 35 0 130 <br />Weathered Bedrock 14 0 124 <br />Bedrock 28 100 124 <br />The parameters for weathered bedrock are much more conservative than those typically encountered in <br />the project area and, it is our opinion, that they are not representative of conditions at the site. <br />We analyzed a vertical highwall section for each phase. The depth to bedrock varied from 7 to 31 feet <br />across the project site. The vertical section corresponds to a steep highwall mining scenario where the <br />highwall inclination is approximately 0.5:1. <br />Table 3 below summarizes the results of our analysis. The analysis was performed using the DRMS <br />parameters shown in Table 2. The factor of safety required by the DRMS for temporary mine slopes <br />and reservoir embankments are provided for comparison. Output graphics for each of the analyses are <br />attached. <br />Table 3: Hi2hwall Setback DRMS Analvsis Resultc <br /> <br />Model Setback <br />Distance (feet) Calculated <br />Facto <br /> <br />er of <br />Saf Required Factor <br /> <br /> <br />of Safety <br />Phase IA 46 1.00 1.0 <br />Phase 1B 39 1.01 1.0 <br />Phase 1C 30 1.04 1.0 <br />Phase 2 Eastside 35 1.03 1.0 <br />Phase 2 Westside 37 1.03 1.0 <br />Phase 3 25 1.11 1.0 <br />Phase 4A 25 1.10 1.0 <br />Phase 4B 25 1.11 1.0 <br />Phase 4C 25 1.16 1.0 <br />Phase 5A 25 1.21 1.0 <br />Phase 5B 25 1.08 1.0 <br />Phase 5C 25 1.25 1.0 <br />Longterm Case 25 1.68 N/A <br />The setback distance in Table 2 is calculated from the crest of the mine highwall to the potential failure <br />surface intersection with the existing ground. <br />Parsons Mine <br />DRMS 112 Permit <br />Page SE7 of SE8
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