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2009-09-21_REPORT - C1981010
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2009-09-21_REPORT - C1981010
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Last modified
8/24/2016 3:55:40 PM
Creation date
12/1/2009 10:15:49 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981010
IBM Index Class Name
Report
Doc Date
9/21/2009
Doc Name
Horse Gulch Fill Stability Analysis, May 2009
Permit Index Doc Type
Waste Pile/Fill Report
Section_Exhibit Name
Appendix T
Media Type
D
Archive
No
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May 29, 2009 <br />Page 6 <br />Table 4. Engineering Properties of Generic Spoil Types (after Douglass and Bailey 1983) <br /> Angle of <br /> Natural Internal <br /> Water Friction Cohesion Plasticity <br />Spoil Type Content Dry Density (total) (total) Index <br /> W YD V c PI <br /> (%) (kg/m3) (degrees) kPa <br />Soil (consists of 75% or more soil 13 to 37 1,380 to 0 to 10 9.6 to 95.8 12 to 30 <br />and slakable rock) (21) 1,750 (5) (57.5) (19) <br /> (1,540) <br />No. of Tests 29 29 9 9 9 <br />Mixed Soil and Rock 9 to 19 1,310 to 4 to 30 19.1 to 134 14 to 32 <br />(13) 2,070 (20) (62.2) (19) <br />(1,680) <br />No. of Tests 44 43 14 14 16 <br />Rock (consists of 10% or less 5 to 15 1,440 to 27 to 32 28.7 to 47.9 14 to 20 <br />soil and slakable rock) (9) 1,910 (29) (38.3) (18) <br />(1,650) <br />No. of Tests 21 20 3 3 6 <br />Note: Numbers in parentheses are median values for the range of data. <br />Median is defined as the value of a variable below and above for which an equal number of variables fall. <br />To convert kg/m3 to pcf multiply by 0.0624, to convert kPa to psf multiply to 20.9. <br />Based on the physical properties observed in the proposed buttress fill area, AAI believed <br />the spoils material would best be modeled as a mix of soil and rock. For the first model runs, the <br />average values for the mixed soil and rock were used. AAI believed that this value would <br />represent the global safety factor of the entire mass of the fill. <br />After a site visit where the author was able to observe the actual spoils piles from the <br />G-Dip Pit (shown in Figure 5) and after reviewing the 2007 drilling program in the G-Pit Slide <br />block, the true nature of the variability became evident. <br />The dragline spoil piles from the G-Dip Pit show the material to be relatively rocky. <br />From the AutoCADTM drawing (Trapper Mining Company 2005), the slope of these spoil piles <br />was measured at 33 to 37 degrees; this indicates the effective friction angle for the <br />unconsolidated material is 37 degrees. However, the material is not homogeneous; there is <br />significant segregation of the large durable rock at the toe of the slope. <br />From the Douglass and Bailey report (1983), a series of regression analyses were <br />preformed relating moisture content and percent soil to the angle of internal friction. This <br />analysis also correlated relative compaction to cohesion. Using the drilling information from the <br />K-Pit Buttress area, the material properties listed in Table 5 were established for use in the <br />computer modeling. The general characteristics of the Horse Gulch fill are presented in Table 6. <br />Using Slope International's Slope-W slope stability software, several model runs were <br />made to determine the sensitivity of the fill properties to the global stability of the fill/clay/rock <br />interface. The section for this analysis is shown in Figure 6. Typical output from Slope-W is <br />shown in Figure 7, followed by Table 6 summarizing the modeling results. <br />Agapito Associates, Inc.
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