TM 5-852-A/AFM 88-19, Chap. 4
America.
and thawing seasons are shown in figure 4-77. During
f.
Design depth of pile embedment. Pile
spring and early summer, piles have greatest potential
bearing capacity in ad freeze bond because of the low
foundations must be designed for sufficient depth of
133
permafrost temperatures during the period . When the
embedment to support the imposed loads in adfreeze
zone of annual thaw and freeze is in the process of
bond without objectionable displacement under the
refreezing, the extremely low temperatures in the frozen
warmest ground temperatures expected, unless suitable
soil near the ground surface cause much higher adfreeze
end bearing on ice-free bedrock or other reliable strata
bond strengths in this area. During the same period of
can be obtained. The piles must also be capable of
seasonal freezing, ground temperatures along the pile
resisting the additional down drag of negative skin friction
length in permafrost are at their warmest and the
from consolidating fill or thawed foundation soils and
corresponding permafrost adfreeze strengths are at their
must provide sufficient anchorage and tensile strength to
weakest. Unless the pile is adequately embedded in the
prevent upward displacement and pile structural failure
permafrost and capable of mobilizing sufficient
from frost heave forces in the annual frost zone in winter.
resistance in adfreeze bond, the pile will heave if an up-
The forces acting on a pile in permafrost during freezing
Point Bearing, QE
U. S. Army Corps of Engineers
Figure 4-77. Stresses acting on piling for typical permafrost condition134.
4-128
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