WORKED EXAMPLES 113
permeabilities, and (2) the construction of the phreatic surface, with
subdivision of the head, H, into increments, ∆h.- From the flownet: Nf3.6, mean Nd≈4.9, and shape factor Nf/Nd
0.73.
k 5.4 10 8 ms^1 (equation (2.15)),EH(core)14.5/29.050%.Worked Example 2.3
Figure 2.15 illustrates the section of a rolled clay embankment dam at an
intermediate state of construction.
GEOTECHNICAL DATA
Rolled clay
core and shoulderUnit weight, (kN m^3 )2 1
Cohesion,c(kNμm^2 ) 05
Angle of shearing resistance (degrees) 30
Estimated pore-pressure ratio, ru Slices 1–30.55
{Slices 4–80.45
Determine the factor of safety, F, with respect to the hypothetical failure
surface indicated using the semi-rigorous Bishop analysis (equation
(2.26b): slice dimensions may be scaled from the figure).
Solution
For an assumed value of F1.5, equation (2.26b) yields F1.71; iteration
(F1.7) confirms F1.72.
Tabulated below are the effects on Fof changing major parameters
involved in the analysis; e.g. c,andru:
Trial c ru F
(kN m^2 ) (degrees)
Slices 1–3 Slices 4–8
A 5 30 0.55 0.45 1.72
B (c) 0 30 0.55 0.45 1.51
C () 5 25 0.55 0.45 1.44
D (ru) 5 30 0.65 0.55 1.41
0.1
0.7329(243600)