TM 5-818-1 / AFM 88-3, Chap. 7
tive measures that may be employed include shading,
minimize adfreeze and frost heave; or cantilevering
reflective paint or other surface material, and sometimes
building attachments, e.g., porches and stairs, to its main
live vegetative covering. In seasonal frost areas, it may
foundation.
(d) In permafrost areas, movement
sometimes be advantageous to color critical surfaces
black to gain maximum effect of solar heat in reducing
and distortion caused by thaw of permafrost can be
winter frost problems. TM 5-852-4/AFM 88-19, Chapter
extreme and should be avoided by designing for full and
4, provides guidance on the control of solar radiation
positive thermal stability whenever the foundation would
thermal effects.
be adversely affected by thaw. If damaging thaw
c. Control of movement and distortion. The
settlement should start, a mechanical refrigeration
amount of movement and distortion that may be
system may have to be installed in the foundation or a
tolerated in the support structure must be established
program of continual jacking may have to be adopted for
and the foundation must be designed to meet these
leveling of the structure. Discontinuance or reduction of
criteria. Movement and distortion of the foundation may
building heat can also be effective. Detailed guidance is
arise from seasonal upward, downward, and lateral
given in TM 5-852-4/AFM 88-19, Chapter 4.
displacements, from progressive settlement arising from
degradation of permafrost or creep deflections under
loads can be carried on the unconfined surface of ice-
load, from horizontal seasonal shrinkage and expansion
saturated frozen soil without progressive deformation.
caused by temperature changes, and from creep, flow,
The allowable long-term loading increases greatly with
or slide of material on slopes. Heave may also occur on
depth but may be limited by unacceptable creep
a nonseasonal basis if there is progressive freezing in
deformation well short of the allowable stress level
the foundation, as under a refrigerated building or
determined from conventional short-term test. Present
storage tank. If the subsurface conditions, moisture
practice is to use large footings with low unit loadings;
availability, frost penetration, imposed loading, or other
support footings on mats of well-drained non-frost-
factors vary in the foundation area, the movements will
susceptible granular materials, which reduce stresses on
be nonuniform. Effects on the foundation and structure
underlying frozen materials to conservatively low values;
may include various kinds of structural damage, jamming
or place foundations at sufficient depth in the ground so
of doors and windows, shearing of utilities, and problems
that creep is effectively minimized. Pile foundations are
with installed equipment.
designed to not exceed sustainable adfreeze bond
(1) Frost-heave
and
thaw-settlement
strengths. In all cases, analysis is based on permafrost
deformations.
temperature at the warmest time of the year. For cases
(a) Frost heave acts in the same
which require estimation of foundation creep behavior,
see TM 5-852-4/AFM 88-19, Chapter 4.
direction as the heat flow, or perpendicular to the
d. Vibration problems and seismic effects.
freezing plane. Thus, a slab on a horizontal surface will
(1) Foundations supported on frozen
be lifted directly upward, but a vertical retaining wall may
ground may be affected by high stress-type dynamic
experience horizontal thrust. Foundation members, such
loadings, such as shock loadings from high-yield
as footings, walls, piles, and anchors, may also be
explosions, by lower stress pulse-type loadings as from
gripped on their lateral surfaces and heaved by frost
earthquakes or impacts, or by relatively low-stress,
forces acting in tangential shear. Figure 18-5 shows an
relatively low-frequency, steady-state vibrations. In
example of frost-heave forces developed in tangential
general, the same procedures used for nonfrozen soil
shear on timber and steel pipe piles restrained against
conditions are applicable to frozen soils. Design criteria
upward movement.
(b) In rivers, lakes, or coastal water bodies,
are given in TM 5-809-10/AFM 88-3, Chapter 13; TM 5-
856-4; TM 5-852-4/AFM 88-19, Chapter 4; and chapter
foundation members to which floating ice may adhere
17 of this manual.
These manuals also contain
may also be subject to important vertical forces as water
references to sources of data on the general behavior
levels fluctuate.
(c) Among methods that can be used to control
and properties of nonfrozen soils under dynamic load
and discuss types of laboratory and field tests available.
detrimental frost action effects are placing non-
However, design criteria, test techniques, and methods
frostsusceptible soils in the depth subject to freezing to
of analysis are not yet firmly established for engineering
avoid frost heave or thrust; providing sufficient
problems of dynamic loading of foundations. Therefore,
embedment or other anchorage to resist movement
the Office, Chief of Engineers, ATTN: DAEN- ECE-T,
under the lifting forces; providing sufficient loading on the
WASH DC 20314, or HQUSAF/PREE, WASH DC
foundation to counterbalance upward forces; isolating
20332, should be notified upon initiation of design and
foundation members from heave forces; battering or
should participate in establishing criteria and ap-
tapering members within the annual frost zone to reduce
effectiveness of heave grip; modifying soil frost
susceptibility; in seasonal frost areas only, taking
advantage of natural heat losses from the facility to
18-10
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