TM 5-852-4/AFM 88-19, Chap. 4
infinite medium, with a suddenly applied constant
permafrost temperature on the time required for
temperature (32F) source which dissipates heat only in
freezeback.
While not specifically shown in figure 4-72, months may
a radial direction into frozen ground of a known initial
14,134
be required to freeze back slurries of 10,000 Btu/ft3 or
. The general solution for the natural
temperature
more volumetric heat capacity at permafrost
freezeback problem, based upon latent heat content of
temperatures between 30" and 32F. Under otherwise
the slurry, is shown in figure 4-71.
identical conditions, a sand-water slurry in 28 F
(j) To determine the time required for
permafrost could freeze back in 2 or 3 days while a
freezeback at different permafrost temperatures, it is
siltwater slurry would take 10 to 11 days; however, in
easier to use a specific solution similar to that shown in
31.5 F permafrost, a freezeback time of about 16 days
figure 4-72, prepared from the general solution. The
would be required for the same sand-water slurry and
specific solution is computed using the known or
about 130 days for the same silt-water slurry. Thus, for
estimated thermal conductivity and volumetric heat
given pile spacings careful selection of the pile type, hole
capacity of the permafrost and the diameter of the hole
size, slurry material, and installation season, plus careful
to be used. As previously noted, allowance for any heat
control of water content, can substantially reduce the
content of the slurry above 32F may be made with
amount of heat which must be absorbed by the
sufficient accuracy by adding this heat content to the
permafrost and the time required for freezeback.
volumetric latent heat, Q; this assumes that the
(k) The preceding general and
placement temperature of the slurry is controlled below
specific solutions
about 40F. The specific solution in figure 4-72 clearly
demonstrates the effect of latent heat of slurry and initial
U. S. Army Corps of Engineers
Figure 4-71. General solution of slurry freezeback rate134.
4-117
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