Civil Engineering Reference
In-Depth Information
Hence,
Bp
tan
4
(45
◦
+
1
2
φ
)
tan
4
55
◦
=
V
l
=
=
3
×
20
×
250 kN
Example 19.3: Drained bearing capacity of a foundation
Better bound solutions for
the foundation in Fig. 19.26 can be found using a mechanism which includes a slip fan
and a stress field which includes a stress fan.
(a) Upper bound. Figure 19.29(a) shows a mechanism consisting of two wedges and
a logarithmic spiral slip fan and Fig. 19.27(b) is the corresponding displacement
diagram. For
φ
20
◦
=
the angles in the mechanism and in the displacement
55
◦
or 35
◦
.
From the geometry of Fig. 19.29(a), and making use of Eq. (19.6) with
1
2
φ
=
diagram are 45
±
ψ
=
φ
,
B
tan(45
◦
+
1
2
φ
) exp(
φ
)
L
=
θ
tan
3 tan 55
◦
exp(
/2 tan 20
◦
)
L
=
π
=
7.6 m
Figure 19.29
Mechanism of collapse for the foundation in Figure 19.26.
