TM 5-852-4/AFM 88-19, Chap. 4
CHAPTER 1
INTRODUCTION
(1) In general, mean annual temperatures
1-1. Purpose and scope.
decrease with increasing latitude or elevation, and the
a. This manual provides criteria and guidance
amplitude of the annual air temperature cycle generally
for design of foundations for structures for military
decreases as large bodies of water or oceans are
facilities in arctic and subarctic regions.
approached. Under natural conditions, mean annual
b. To facilitate the use of this manual,
ground temperatures are usually 2 F to 5 F higher than
superscript numbers are used to refer to Appendix A-
mean annual air temperatures, though deviations are
References. These references have been divided into
sometimes outside this range. The difference between
publications required to use the manual (Required
air and ground temperatures is attributable primarily to
Publications) and additional related publications (Related
additional heat input from absorption of solar radiation at
Publications.)
the ground surface in the summer, to restriction of heat
loss by the insulating effect of a snow cover during the
1-2. Environmental conditions in the Arctic and
winter months, and to the normal temperature difference
Subarctic.
which occurs in heat flow across a solid/gas interface.
The design, construction and maintenance of
Mean annual air temperatures in the Northern
foundations are all affected by the special environmental
109, 110
Hemisphere are shown in TM 5-852-1'.
.
conditions found in the Arctic and Subarctic
(2) Air
temperatures
in
arctic
(Superscript numbers indicate references listed in app
environments may range from highs of 75 ƒF to 85 F in
A.) These conditions typically include the following, as
the summer to lows of -50F to -75 F during the coldest
applicable:
winter months. It is not uncommon for air temperatures
to remain below -30F for a week or more at many
Seasonal freezing and thawing of
locations in Alaska and in fact air temperatures have
ground with attendant frost heaving and
remained below -50F for as much as several weeks. A
other effects.
typical record of air temperatures for a one-year period at
Occurrence of permanently frozen
Fort Yukon is shown in figure 1-1, along with other data,
ground subject to thawing and
including ground temperatures.
subsidence
during
and
following
b. Front conditions.
construction.
(1). Seasonal frost areas are those areas
Special physical behavior and properties
where significant freezing occurs during the winter
of frozen soil, rock, and construction
season but without development of permafrost. In North
materials at low temperatures and under
America significant seasonal frost occurs about I year in
freeze-thaw action.
10 in northern Texas. A little farther to the north it is
Difficulty of excavating and handling
experienced every year. As indicated in figure 1-2, depth
frozen ground.
of seasonal freezing increases northward with
Poor drainage and possible excess of
decreasing mean annual air temperature until permafrost
water during thaw caused by the
is encountered. With still further decrease of mean
presence of impervious frozen ground at
annual temperature, the zone subject to annual freezing
shallow depths.
164
and thawing becomes progressively thinner
Thermal stresses and cracking.
174
(2) Permafrost areas are those in which
Ice uplift and thrust action.
perennially frozen ground is found. In North America
Limited
availability
of
natural
permafrost is found principally north of latitudes 55 to
construction materials, support facilities,
65ƒ, although patches of permafrost are found much
and labor.
farther south on mountains where the temperature
Adverse conditions of temperature,
conditions are sufficiently low, including some mountains
wind,
distance,
in the United States. The depth to the surface of
accessibility, working seasons, and cost.
permafrost is dependent primarily on the magnitude of
While these factors are important in many other types of
6
3
the air thawing index, the radiational input to the surface
construction such as pavements and utilities , they merit
(as controlled by such factors as latitude, amount of
separate consideration for foundations for structures.
cloudiness, degree of shading or exposure, vegetation,
a. Temperature. The single most important
and surface color), and the water content and dry unit
factor contributing to the existence of these adverse
weight of the soil.
conditions in the northern regions is the prevailing low air
(a) In
zones
of
continuous
temperatures, demonstrated not only in the intensity and
permafrost, frozen
duration of cold in winter itself but also in the low mean
annual temperatures.
1-1
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