Civil Engineering Reference
In-Depth Information
N
Great circle
plane A
Great circle
plane B
Pole of
plane B
na.nb
Pole of
plane A
N
b
N
a
1.nb
2.nb
1
2
24
Great circle
of face
13
45
5
35
5
4
Great circle of
upper surface
3
Direction of sliding
Figure 7.7
Stereoplot of data required for wedge stability analysis.
pressures is important because the value of these
parameters are difficult to define precisely.
Table 7.1
Parameters defining properties of
wedge
Plane
Dip Dip
Properties
7.5 Wedge stability charts for friction only
A rapid check of the stability of a wedge can be
made if the slope is drained and there is zero cohe-
sion on both the slide planes A and B. Under these
conditions, equation (7.9) reduces to
direction
20
◦
,
c
A
=
A
45
105
φ
A
=
24 kPa
30
◦
,
c
B
=
B
70
235
φ
B
=
48 kPa
Slope face
65
185
Upper
surface
12
195
FS
=
A
tan
φ
A
+
B
tan
φ
B
(7.14)
varying the water density to simulate the effect
of reducing the water pressure. In this example,
the factor of safety is 1.98 when the slope is
completely drained.
As has been emphasized in previous chapters,
this ability to check the sensitivity of the factor of
safety to changes in material properties or water
The dimensionless factors
A
and
B
are found to
depend upon the dips and dip directions of the
two planes. The values of these two factors have
been computed for a range of wedge geometries,
and the results are presented as a series of charts
(Figures 7.8-7.15).
