Download Slope stability analysis of tailings dam embankments

5.3.1
Stability charts results
Table 5.5: Case 2 factor of safety from stability charts
Analysis
Undrained
Taylor
Bishop &
Morgenstern
Spencer
Janbu
0.656
n/a
n/a
0.656
n/a
1.266
1.038
n/a
Drained
For undrained analysis, Taylor and Janbu’s stability charts gave the same factors of safety as
in Case 1 (i.e. the change in phreatic surface did not affect the factor of safety). Bishop and
Morgenstern’s and Spencer’s stability charts gave different factors of safety for the drained
condition compared to Case 1, since the pore water pressures were now included. The pore
pressure ratio (𝑟𝑢 ) calculated for Bishop and Morgenstern’s stability charts was 0.33, however
for use in Spencer’s method 𝑟𝑢 = 0.25 which accounts for the differences between the two
factors of safety.
5.3.2
Undrained analysis
Table 5.6: Factor of safety from Case 2 Spreadsheet and SLOPE/W for undrained conditions
Method
Bishop
simplified
Fellenius
Janbu
simplified
Morgenstern
and Price
Spencer
General
limit
equilibrium
Spreadsheet
0.755
0.755
n/a
n/a
n/a
n/a
SLOPE/W
0.748
0.748
0.730
0.757
0.757
0.756
Spreadsheet
0.735
0.735
n/a
n/a
n/a
n/a
SLOPE/W
0.730
0.730
0.719
0.735
0.735
0.730
No. of
slices
5
20
0.730
Elevation (m)
15
10
5
0
0
5
10
15
20
25
30
35
40
Distance (m)
Figure 5.7: Most critical slip circle in undrained SLOPE/W analysis with 20 slices
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