TM 5-852-1/AFR 88-19, Volume 1
c. Surface index-air index ratios or n-factors
-Pavement pumping.
-Pavement cracking.
provide measures of the effects of different surface
-Deterioration of pavement surfacing.
conditions. A table of such values is given in TM 5852-
-Progressive increase of pavement roughness.
4/AFM 88-19, Chap.
4.
Calculation methods for
-Loss of compaction.
prediction of depths of freeze and thaw in soils are
-Restriction of subsurface drainage by frozen
presented in TM 5-852-6/AFR 88-19, Volume 6.
d. Changes in the thermal regime may in turn
ground.
-Wintertime surface drainage problems.
affect the frost heave, seasonal thaw-settlement, or
-Snow removal and icing problems.
thaw-weakening behavior of the supporting soils. In
-Degradation settlement from thawing of
permafrost areas, degradation will produce progressive
permafrost, commonly differential.
settlement if thaw-unstable soils containing excess ice
-Adverse surface drainage effects from permafrost
are present. Such potential effects should be anticipated
degradation.
and taken into account during design.
All but the last two effects may also be observed in
5-2.
Site selection and development
temperate zone frost areas, but in the Arctic and
a. All design for construction in arctic and
Subarctic freezing is more intense and more prolonged.
subarctic regions must be preceded by thorough site or
The thawing and thaw-weakening periods are also longer
route investigations to obtain any existing information on
and in permafrost areas last until freezing starts again
the proposed location plus new field data on surface and
after the summer. The most difficult conditions are in the
subsurface features, drainage, permafrost and other
area near the boundary between permafrost and
conditions as needed. Environmental impact must be
unfrozen soils where depth of seasonal freezing is
considered as discussed in chapter 3. The importance
maximum and permafrost, where present, is the least
of thorough site investigations before construction cannot
thermally stable. The detrimental effects of seasonal
be overemphasized. Sites with non-frost-susceptible
frost action on pavements are discussed in TM 5-818-
foundations are much easier to develop than those
2/AFM 88-6, Chap. 4. In permafrost regions, the
having frost-susceptible materials.
change of surface conditions caused by construction
b. Site selection and development in the Arctic
may begin permafrost degradation, particularly in the
and Subarctic may often be much more complex than in
discontinuous permafrost zone. This degradation will
the temperate regions because of the relative lack of
result in settlement. If the permafrost contains excess
existing information, the large areas and distances
ice, the settlement will invariably be differential. Criteria
sometimes involved, the limited support facilities, and the
and guidance for runwav and road design in arctic and
seasonal and environmental constraints on field
subarctic areas are presented in TM 5-852-/AFM 8S19,
activities. Over large areas of the Arctic and Subarctic,
Chap. 3.
specific terrain or local climatic information may be
limited or nonexistent.
Heavy reliance on air
5-4.
Foundations for structures
reconnaissance and air-photo studies may be required.
a. The following principles must be considered
Access to proposed site or route locations may be
for foundation design in areas of permafrost:
difficult and expensive, may require careful seasonal
scheduling, and may involve severe restraints on sizes
Foundation supporting
Foundation supporting
and weights of survey equipment that can be brought in.
conditions not adversely
conditions adversely
Field working conditions may sometimes be difficult.
affected by thaw
affected by thaw
Safety aspects of field activities may be significant
considerations. Costs of site selection and development
Use normal temperate
Consider following options
studies may be high but cost should not be allowed to
zone approach
serve as justification for inadequate investigations.
1.
Maintenance of
Procedures for site selection and development studies
existing thermal
are presented in TM 5-8522/AFR 88-19, Volume 2.
regime.
2.
Acceptance of the
5-3.
Airfield pavements and roads
changes in the
thermal regime to be
The following detrimental effects, which may occur in
caused by the
airfield pavements and roads in the Arctic and Subarctic,
construction and
should be considered in design:
facility, and allowance
-Seasonal frost heave and settlement, commonly
for these in design.
differential.
3.
Modification of
-Reduction of bearing capacity during and after
foundation conditions
thaw.
prior to construction.
5-2
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