01 July 1997
(2) Pile Toe Settlement. A computation of pile toe settlement is given in figure 5-11.
(3) Summary of Settlement Analysis Results. A summary of the results of the settlement
computation (with actual data for Pile E2) is given in table 5-2.
b. Indicator Pile. Following the static load test, an indicator pile of the same dimensions and type as
the production piles were driven between groups S-4 and S-5, near pile S-5-1. The pile was driven with the
same Delmag D46-23 hammer that was used in the production driving. A comparison of the driving record
of this pile with that of test pile E2 or pile S-5-12 is shown in figure 5-13. This figure shows that the blow
counts of the indicator pile are substantially larger than those of pile E2 or S-5-12, especially below -40 feet
MSL. The blow count at final penetration of the indicator pile at about -81 feet is approximately
20 blows/foot. This value is well within the 6 to 37 blows/foot observed at the toe depths of groups S-1, S-2,
N-1 and N-2, but greater than the 3 to 12 blows/foot observed at the toe depth for groups S-4 and S-5. The
mean penetration resistance of this pile is the same as or exceeds the largest mean value observed during
the driving of any of the piles in the North groups. This observation is consistent with the mechanisms of
sand densification during pile installation and recementation during driving, such as the result of sand
densification may have dissipated shortly after driving.
c. Restrikes of Production Piles. Figure 5-14 shows the comparison of the blow counts of those pile
restruck with their original blow counts. As was the case with the indicator pile, the same hammer used to
driving the piles originally was used to restrike them.
d. Results of Supplemental Test Program. This program showed that the existing pile foundation has
adequate bearing capacity to support the drydock and that the original specification for the project led to an
adequate foundation. During the production driving, excess pore water pressures, sand densification, and
increased confining stresses during driving lead to blow counts that were below expectation. However, in
this case these phenomena reversed themselves after driving, leading to soil freeze and increased blow
counts during restrikes and thus increased bearing capacity over time. Ultimate bearing capacity evaluated
by dynamic monitoring using the pile driving analyzer was consistent with results of static load tests.
5-4. LESSONS LEARNED. In addition to the detailed geotechnical aspects of the Kwajalein project, there
are some important overall lessons that are to be learned from this experience.
a. Complete Environmental Requirements. Districts must assure that complete, documented
approval of the fulfillment of all existing environmental requirements, including those under the National
Environmental Policy Act (NEPA), are in place prior to contract award. Failure to do this can result in
significant delays and costly modifications to the project. Environmental requirements relating to
construction must be addressed and approvals obtained and fully documented prior to the beginning of
b. Complete Thorough Soil Investigation. Subsurface investigation should be thorough, complete,
and span the full range of site investigations.
c. Complete Driving of Indicator Piles. Any indicator or test pile program should be planned from the
start, locating the piles to reflect the range of potential site conditions. The piles should be driven before the
production piling is started and load tests be applied to the piles after a minimum waiting period, usually
1 day. The driving of these piles, along with all other testing, should be handled with a separate contract
from the production piling.
d. Establish Criteria for Restrikes and Setup Time. If piles are in coral or other cemented sand strata,
a setup time should be considered and a set duration time established in the design. The load test program