TM 5-852-1/AFR 88-19, Volume 1
Table 4-1. Depths to the permafrost layer at the end of the thawing period of two typical locations.
Depth to surface of permafrost layer (ft)
Arctic:
Subarctic:
mean annual temp.
mean annual temp.
10 to 12F,
26cF,
mean thawing index
mean thawing index
Surface and subsurface conditions
500-600 degree-days (F)
3200 degree-days (F)
Treeless area with 6-inch-thick moss
a
1.5 to 2.0
5.0 to 6.0
cover over silt soil (w = 30-40%)
Asphalt pavement over 8 feet of sandy
gravel base (w = 4%) and silt subgrade
b
(w = 30-40%)
7.0 to 8.0
12.0
a
w = water content in percent of dry w-eight of soil.
b
Six years after construction, a degrading condition.
d. Thickness. The thickness of the permafrost
e. Soilfactors.
As a rule, the
layer generally increases with increasing latitude, being
characteristics of permafrost will depend upon the
greater in arctic than in subarctic regions. The greatest
texture, water content and temperature of the soil.
depths of permafrost occur in the nonglaciated areas of
Relatively clean sands and gravels located in well-
the continuous zone. In Siberia, a record depth of 4900
drained positions may not present serious engineering
feet to the permafrost base has been reported. It has
construction problems if they do not contain appreciable
been estimated that the maximum thickness of
amounts of excess ice.
Conversely, permafrost
permafrost in arctic Canada may exceed 3000 feet, and
consisting of fine-textured soils such as silt often
in arctic Alaska it may be over 2000 feet. The greatest
contains large formations of ice in lenses, layers,
depth so far measured in Canada is about 1700 feet at
wedges, veins or other shapes. TM -852-4/AFM 88-19,
Winter Harbour, Melville Island. A depth of 1600 feet
Chap. 4 presents information on the strength and other
has been estimated at Thule, Greenland.
Other
properties of frozen soils. MIL-STD-619B presents a
observed depths are about 1300 feet south of Barrow,
standard system for classification of frozen soils.
Alaska, and at Resolute, Northwest Territories; about
920 feet at Umiat, Alaska; and about 170 feet at
Northway, Alaska.
4-5
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