TM 5-852-4/AFM 88-19, Chap. 4
manently frozen sands, gravels, and bedrock cannot be
construction sites. It is possible that local sand and
automatically assumed to be free of ice inclusions such
gravel deposits may be found quite loose or containing
as lenses or wedges (para 2-5).
However, such
ground ice due to various causes, such as silt inclusions
foundation materials, free of excess ice, do occur
within the soil mass, and some settlements may occur at
frequently, as in important areas of interior Alaska.
such points if thawed materials are reconsolidated under
When clean sands and gravels, or bedrock free of
the effects of loading and/or vibrations. Whether or not
ground ice, are present, foundation design can frequently
such conditions are present in significant degree must be
be identical with temperate zone practice, even though
determined in the course of the site investigations, and
the foundation materials are frozen below the foundation
whether or not they need be taken into account in the
level.
Seasonal frost heave and settlement are
design and construction will depend in part on the type
comparatively small or negligible in clean, granular, non-
and importance of the structure. Often, measures to
frost-susceptible materials under nominal confinement.
preserve permafrost are unnecessary in construction on
When such materials thaw they remain relatively stable
deep, clean sand and gravel deposits. Figure 4-3 shows,
and retain good bearing characteristics. The tendency of
for example, the very minor settlement which
freedraining sand and gravel deposits to have low
accompanied thaw progression under a three story
ground water levels, within limits set by surrounding
reinforced concrete
terrain, contributes to their general desirability as
U. S. Army Corps of Engineers
Figure 4-3. Thawing of permafrost under 3 story, reinforced concrete, 500-man barracks, Fairbanks,. Alaska. Reference
points consisted of bolts installed in outer side of foundation wall above ground100.
4-3
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