Civil Engineering Reference
In-Depth Information
48”
φ
24 m (80 ft)
2
5 mm (1”)
87 m (290 ft)
24 m (80 ft)
24 m (80 ft)
36 m (90 ft)
34 m (110 ft)
3
0
mm (1”)
24 m (80 ft)
2
5
mm (1”)
24 m (6
0 ft)
1
9
mm (3/4”)
1
6
mm (5/8”)
2
5
mm (1”)
22 (7/8”)
60 m (200 ft)
42 m (140 ft)
3 m (10 ft)
FIGURE 4.13
Example of design and assembly for offshore pile
when choosing the pile thickness and also the service life of the piling, because
there should be a corrosion allowance to cover the corrosion effect during the
platform
s lifetime.
For piles that are to be installed by driving, where sustained hard driving of
820 blows per meter with the largest size hammer is anticipated, the minimum
piling wall thickness should be more than
'
t
=
6
:
35
+
D/100
(4.51)
where t = wall thickness (in inches or mm) and D = diameter (in inches or mm).
The requirement for a smaller D/t ratio when hard driving is expected may
be relaxed when it can be shown by past experience or by detailed analysis that
the pile will not be damaged during its installation. A typical example of pile
thickness at different depths is shown in
Figure 4.13
.
4.8.4 Driving Shoe and Head
The driving shoe and head are usually the responsibility of the contractor, with
approval from the engineering office. The purpose of the driving shoes is to
assist piles in penetrating hard layers and to reduce driving resistances. Note
that different design considerations apply for each use.
If the soil report indicates that there is a hard layer, the driving shoe should
be designed to prevent high driving stresses at and above the transition point
between the normal and the thickened sections at the pile tip.
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