Civil Engineering Reference
In-Depth Information
depth of the mesh in the
-direction is 40 m
d1=40
, and the boundary condition parameter
is set to
ifix=2
implying a line of symmetry at the
z
z
=
40 m plane (rough-smooth), so
the “actual” embankment has a depth of 80 m.
Three-dimensional analysis involves very significant storage requirements compared
with 2D, so the example involves a quite crude mesh with 5 slices of elements in the
z
-direction
nze=5
. In this case the slope is assumed to have a linearly varying undrained
strength varying from 60 kN/m
2
at the abutment to 40 kN/m
2
at the centreline. There are
thus 5 property types (
np types=5
) in the data file, one for each slice.
The
etype
data maps the properties onto the elements, which are numbered, starting at
the origin, first in the
x
-direction, then in the
y
-direction (top to bottom) and finally in the
z
-direction. The tolerance
tol
and iteration ceiling
limit
are set as usual, followed by
the number of trial strength reduction factors
nsrf
and the strength reduction factor values
read into
srf
. The iteration ceiling has been set higher than usual at 1,000 to emphasise
the onset of failure.
The output from the analysis is given in Figure 6.46 and plotted in Figure 6.47. The
results indicate that the factor of safety of the slope is about 1.6. Figure 6.48 shows the
There are 2972 equations and the skyline storage is 1538004
srf max disp iters
1.00 0.2266E-01 16
1.40 0.3123E-01 77
1.50 0.3930E-01 208
1.55 0.4971E-01 380
1.58 0.6363E-01 703
1.60 0.9308E-01 1000
Figure 6.46
Results from Program 6.10 example
d
max
Iterations
16
77
208
380
FS
≈
1.6
703
1000+
SRF
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
Figure 6.47
Plot
of
maximum
displacement
versus
Strength
Reduction
Factor
from
Program 6.10 example
