TM 5-852-4/AFM 88-19, Chap. 4
Table 2-1. Approximate Coefficients of Linear Thermal Expansion perC.
-6
x 10
Granite and slate
8
Portland cement concrete
10
3
Soil (109 lb/ft , 23 % water content, +20 to -160c)
22
Ice
51
Steel
12
Copper
14-17
Aluminum
18-23
Sulfur
64
Coal tar pitch
160
Asphalt
215
Roofing felt
11-33
Built-up roofing membranes
15-53
Bakelite
22-33
Some other plastics
35-90
Wood (pine), parallel to fiber
5.4
Wood (pine), perpendicular to fiber
34
Note: The coefficient of cubical expansion may be taken as three times the linear coefficient.
shrinkage with lowering temperature.
strength may also serve to alter and control contraction
h. The ground surface experiences substantial
cracking of the ground.
i.
Thus, foundation materials and structures in
contraction as it is cooled in the fall and winter months,
207
resulting in cracking of the surface . In arctic and
arctic and subarctic regions must be viewed as subject to
160 206
subarctic areas patterned ground is formed , , with
continual changes in conditions and in their states of
ice wedges at the boundaries of the resulting polygons,
stress and strain. It must be the designer's objective to
as illustrated in figure 2-2. (For additional information on
keep such movements and stresses within acceptable
surficial features such as patterned ground, see TM 5-
limits and without progressive changes detrimental to the
17
852-8 .) In far northern areas the maximum surface
facility.
cracking effects tend to develop in the spring, even as
late as May or June, as the effects of the winter low
2-2. Seasonal frost heave and settlement.
temperatures reach substantial depths below the
surface. Shrinkage cracking of flexible pavements is
a. Frost heave may be anticipated whenever
observed in all cold regions and ground cracking has
freezing temperatures advance into frost-susceptible soil
been observed in seasonal frost areas as well as the
and adequate moisture is available, provided it is not
207
permafrost regions . During the summer and fall,
restrained by a countermeasure. Seasonal heave and
expansion of the warming ground may exert substantial
settlement of frost-susceptible soils occur in both
horizontal thrust if cracks have become filled with soil or
permafrost and seasonal frost regions in the surface
ice. Any construction features embedded in the layers of
strata subject to cyclic freezing and thawing. Heave or
ground subject to these seasonal thermal contraction or
settlement may also occur on a nonseasonal basis if
expansion effects, or supported on them, may in
progressive freezing or thawing is caused in the
consequence have stresses imposed upon them.
foundation.
Where items such as power cables or pipes cross
b. During the freezing process the normal
contraction cracks, stresses may be sufficient to rupture
moisture of the soil, and that drawn up from greater
or damage these members. Structures supported above
depths, is converted into ice as crystals, lenses or other
the surface may also experience such effects if the
forms. In
strains are differential and if these can be transmitted
through the supporting members. Structures of sufficient
2-3
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