EI 02G001
CEMP-E
01 July 1997
b. Ultimate Pile Capacity. As is the case with any pile driving project, there were several ways
available to determine the load-bearing capacity of the piles.
(1) Wave Equation Analysis. A wave equation program was used to analyze the bearing capacity
of the piles. Using this method, it is necessary to know the configuration of the hammer and pile, the soil
tape, the distribution of the bearing capacity of the soil between the shaft and the toe, and also the
distribution of the shaft resistance along the length of the shaft including the length of the pile embedment.
The driving resistance for the pile can then be varied, and the various blow counts for each case can be
calculated by the program. The results of this analysis for the Kwajalein piles are shown in figure 5-6.
(2) Application of Design Methods. Other methods that can be employed to estimate the bearing
capacity of the piles are (a) dynamic formulae and (b) methods which are based on the properties of the
soils themselves. The dynamic formulae have been largely superseded by the wave equation. A
discussion of these for the piles in question is given in Miscellaneous Paper GL-92-23. Capacity estimation
from the soil properties themselves is shown in figure 5-7. A more detailed explanation of the Meyerhof and
Nordlund methods is given in TM 5-809-7, along with detailed instructions on the use of these methods.
(3) Load Test. Piles E2, E3, and C2 were tested with static loads 1 to 5 days after installation. For
pile E2, the results of the load test is shown in figure 5-8. This result is consistent with the estimates given
by the analytical methods. The load tests were performed 1 to 5 days after installation, and this could allow
for soil freeze, perhaps from dissipation of excess pore water pressure. The effects of soil freeze are seen
in figure 5-9, which compares the penetration resistance during the original driving with a restrike 12 to
24 hours after original driving. Results of this restrike are shown in figure 5-9.
c. Settlement. Settlement was estimated using the design load and Vesic' semi-empirical method,
s
where the total settlement is the sum of the axial deformation of the shaft, the settlement at toe from load
transmitted along the pile shaft, and settlement at toe from load transmitted at the toe.
(1) Axial Compression. A computation of axial compression is given in figure 5-10.
Table 5-2. Summary of settlement analysis.
Total Settlement
Pile
Case
mm
inches
Headwall
50 percent shaft,
8.1
0.32
50 percent toe resistance
100 percent shaft resistance
2.4
0.095
Proof Test, Pile E2
1.8
0.07
Far End
50 percent shaft,
35.0
1.38
50 percent toe resistance
100 percent shaft resistance
5.3
0.21
(4) Comparison with Load Tests. Settlement of the proof load test conducted on Pile E2 near the
head wall (figure 5-8) shows about 0.07 inch at the design load of 120 kips for offshore piles. This
5-4
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