Assessment of Existing Structures and Repairs - Offshore Structures: Design, Construction and Maintenance - page 472

200

>101 m
51-100 m

180

60

31-50 m
0-30 m

40

20

00

30

60

40

20

0

Year

FIGURE 7.1 Bar chart of development with water depth.

earth pressure coefficient, K, which changed from 0.7 to 0.8. For the third to tenth
editions (1972 to 1984), there is a reduction in ultimate compressive capacity of
up to 30% for a given pile length if K is taken as 0.5.
The ultimate tensile capacity predicted by the recommendations in the first
edition is almost identical to that in the third edition. However, the ultimate ten-
sile capacity has been increased by up to 50% for the same pile length according
to the fifteenth edition. In terms of pile length for a given pile load, the fifteenth
edition leads to a reduction of around 7 m for this example.
Table 7.6 presents the ultimate capacities for a pile with a diameter of 1 m
and a depth of 30 m in homogeneous dense sand.
Table 7.7 presents the ultimate capacity for 30 m penetration in homogenous
normally consolidated clay.
This table and Figure 7.4 illustrate the significant reduction in ultimate pile
capacity for guidance in the sixth edition, particularly at deeper penetrations.
The seventeenth edition guidance has led to a reduction in capacity of around
25% from the guidance introduced in the seventh edition for a given pile length.
In terms of pile length for a given capacity, the seventeenth edition leads to an
increase of around 9 m for this example.
Note that there is no longer a difference between the pile ultimate tensile and
compressive capacity for different editions in normally consolidated clay.