TM 5-852-4/AFM 88-19, Chap. 4
Figure 4-76. Influence of slurry on temperature of permafrost between piles134.
such temperatures problems of slurry freezeback are
work tends to be hampered by ground water, sloughing
greatly reduced. If augering is accomplished prior to
of soils in holes, slow freezeback, and a loss of
start of thaw in spring or early summer, the holes
equipment mobility on the ground surface unless a
normally require no casing and are not subject to filling
granular mat is placed. Even though the ground surface
with melt water. Augering cold frozen soils requires no
may be frozen in fall, a residual thaw zone may still be
additional power; in fact cold frozen cuttings are easier to
present well into the winter, possibly requiring a casing to
displace at the surface when spin-removed and are
seal off ground water and sloughing soil. Early winter is
easier to shovel or scoop up for removal or use in the
also unfavorable because air temperatures are often
slurry. Snow on the ground surface may be partially or
uncomfortable, there is minimum daylight for work, and
completely removed, but compacted snow offers a good
ground temperatures in the permafrost are near their
working surface which helps to protect vegetative cover.
warmest.
(c) On the other hand, piles which
Compaction of snow greatly reduces the insulation value
of the snow cover, permitting colder temperatures to
are to be driven into frozen soil can be best driven in the
develop in late winter.
early winter. In the spring, open-ended pipe piles are
(b) Most
construction
contracts
somewhat more difficult to drive than in the early winter
involving slurried piles are awarded so as to permit the
because of colder permafrost temperatures, the
contractor to install piles in late winter or spring, thereby
presence of the seasonal frost layer and the tendency of
allowing the work to progress throughout the summer,
the soil plug developed inside the pipe to wedge against
with the structure being closed in against weather by late
the sides. This wedging action can develop to an extent
fall. If the pile installation is done in summer and fall the
4-123
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