Civil Engineering Reference
In-Depth Information
3.5
Sheet pile walls, h = 3.5 m
1 m thick slurry walls, h = 3.5m
3
h
2.5
Factor of Safety against
basal ground heave
2
0.9
Increasing system stability
1.0
1.5
1.1
1.4
1
2.0
0.5
3.0
0
10
100
1000
10000
γ
w
h
avg
4
)
System stiffness (EI)/(
Figure 6.24
Normalized maximum wall movement as a function of system stiffness.
that walls with the same flexibility number,
γ
h
4
/
(
EI
) will give rise to the same
δ
h
max
/
h
,
δ
v
max
/
d
2
h
, where
d
is the excavation
depth and
h
is the average prop spacing (or maximum spacing if significantly different)
or in the case of a cantilever is the depth to an effective point of fixity.
It is concluded that in relation to the Clough and O'Rourke chart and
for stiff soils
with a large factor of safety against excavation base heave:
h
and sum of the normalized prop forces,
F
/γ
1 Normalized maximum lateral movement values
δ
h
max
are frequently between
0.05%
H
and 0.25%
H
where
H
is the excavation depth.
2 Normalized maximum vertical settlement values,
δ
v
max
are usually lower with
values frequently between 0 and 0.2%
H
.
3 There is no discernible difference in the performance of propped, anchored or
top-down systems.
4 The values recorded are somewhat less than would be expected from the Clough
and O'Rourke (1990) chart, possibly because the soils are on average stiffer than
originally assumed by the authors.
