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2011-11-30_PERMIT FILE - C1981008 (8)
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2011-11-30_PERMIT FILE - C1981008 (8)
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Last modified
8/24/2016 4:45:30 PM
Creation date
12/20/2011 9:31:28 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981008
IBM Index Class Name
Permit File
Doc Date
11/30/2011
Doc Name
Pond Embankment Slope Stability Analyses
Section_Exhibit Name
Section 2.05.3(3) Attachment 2.05.3(3)-15
Media Type
D
Archive
No
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Note: The grid used to perform the search of the center of the circle with the weakest factor of <br />safety was selected to avoid the inside part of the embankment. Failure on this side would only <br />occur due to rapid drawdown which is not possible due to the type of principal spillway system used <br />in the pond. See pond design section of the permit. <br />The case runs of Appendix 1 show that the grid search uses an increment of 2.0. Since the factors <br />of safety for all cases are above the required factor of safety of 1.3, no additional searches have <br />been run using a lower increment, since there is no way the factor of safety could be below the <br />required amount. <br />6. Conclusions <br />Case 1 shows a scenario where the embankment has conservative strength parameters but the <br />foundation material has a conservative cohesion and friction angle but a slightly higher density than <br />that measured on the site. The safety factor of 1.82 shows the good stability of the pond dam. <br />Case 2 uses the most conservative values in the ranges given for both soil types from Table 1. The <br />results still show a factor of safety (1.54) well above the required amount of 1.3. This is strong <br />evidence that the ponds will not fail. <br />Case 3 uses parameters for both soil types which are far weaker than even the lowest values from <br />Table 1. This could be considered beyond worse case and the factor of safety (1.37) is still <br />significantly above the required limit. The failure circle, center and radius for this case have been <br />added to Drawing 1 of this report. <br />Case 4 is the most likely case using middle of the road strength parameters from Table 1 and <br />densities measured from actual samples of the material. The safety factor of 1.75 is very good. Note <br />that no cohesion was used for the foundation material and it is possible that some cohesion will <br />exist here. <br />Case 5 uses conservative strength parameters for both soils except a low cohesion value was given <br />to the foundation material assuming some clays will be present. The safety factor of 2.22 shows <br />that any cohesion in the foundation greatly increases the strength of the embankment, although it <br />is not needed to pass the requirements. <br />Case 6 is the same as Case 5 except that a higher cohesion was assumed for the embankment <br />material. The safety factor of 2.32 shows that a much higher cohesion of this material does not <br />greatly increase the factor of safety over the previous case. Nevertheless, any cohesion in the <br />Attachment 2.05.3(3) -15 -10 <br />
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