TM 5-852-4/AFM 88-19, Chap. 4
ly inadvisable at a structure site.
conventional procedures before spreading of the next
i.
Rock excavation presents no more difficult
layer of frozen material. The Corps of Engineers Alaska
a problem at air temperatures between 32 and 0F than
District reports that be using procedures designed to
at temperatures above freezing, except that rock
insure the most favorable results, moist thawed silts
containing appreciable moisture is likely to be difficult to
have been borrowed and placed at 95 percent of
transport and handle between 15 and 32F because of
modified AASHTO density during 0 to 30F weather
its tendency to freeze to surfaces. Blasting and mucking
using heavy vibratory compactors. They suggest that
operations should be coordinated because the blasted
vibratory grid roller or vibratory sheepsfoot compaction
rock, providing many channels for moisture penetration
should be most effective. Similar experiences have been
such as from snow or rain, can freeze into a mass which
reported in New England with sheepsfoot roller
must be reblasted. As noted above, large rippers may
compaction using rapid processing to achieve
be effective in some rock. Rock, if in large pieces or
compaction before significant freezing. Others have
without moisture, seldom freezes to truck bodies;
concluded that the minimum practical and economical
however, this can be a major problem with moist soil or
temperature for placing common backfill is about 20 F
113
and for placing granular materials, 15F . Success is
rock containing fines, especially if hauled a considerable
any of the recorded cases of successful below-freezing
distance. To control this, many contractors in Canada
embankment placement has depended on one or more
have equipped their dump truck bodies with muffler
of the following alternatives: rapid and continuous
extension pipes to heat the bodies with otherwise lost
placement so as to achieve compaction before freezing,
engine heat.
use of CaCI,, added in advance, to lower the freezing
temperature, or use of dry, cohesionless, non-frost
6-3. Embankment and backfill.
susceptible materials.
a. All personnel responsible for design and
b. During freezing weather, earth handling and
construction of projects to be constructed in cold
placement of ordinary soils should be continuous to
climates should be aware of the extent to which
avoid formation of thick layers of frozen material which
construction of embankments, fills, and backfill may at
will not thaw quickly if incorporated into the embankment.
the same time be both possible and limited. On the one
The foundation or surface of the fill should be checked
hand, placement of embankments may be accomplished
for frozen material before proceeding with the next lift.
most readily in winter when the ground is frozen, if the
All frozen material should be removed. It should not be
natural surface is impassable in the summer, provided
disced in place. If poor-drainage material is used, the
suitable fill materials are used. On the other hand,
temperature of the material should be above freezing
construction of load-bearing fill which will be used to
and it should be placed and compacted at the proper
support an overlying facility may be difficult to
moisture content. The fill should than either be protected
accomplish successfully in the winter season because of
from freezing or all frozen material removed before
the problems of freezing of moist material before it can
additional backfill is placed. Under no circumstances
be compacted or of excluding lumps of frozen materials
should frozen material, from stockpile or borrow, be
which may result in later thaw-settlement.
It is
placed in fill or backfill which is to be compacted to a
impossible to compact most soils to specified densities
specified density. Extreme precautions should be taken
with available equipment and techniques when the soil
regarding the possible entrance of excess water from
temperature drops below about 30F, that is, after the
wastewater, curing water, or during thaws into areas of
soil has frozen. However, successful embankment, fill,
compacted fill. The use of additives, such as calcium
or backfill placement under winter conditions, at very low
chloride, will lower the freezing temperature of soil, but
ambient temperatures, has been accomplished by
they will ordinarily also change the compaction and
stockpiling very clean, gravelly materials in the summer
moisture requirements'. Experience with salt has been
months in such a way as to promote drainage to very low
mixed. Therefore, additives should not be used unless a
water contents; such material can be handled and placed
prior laboratory study of compaction and additive
with effectiveness acceptable for many purposes under
percentage requirements is made. If used, additives
the coldest temperatures. It is possible that dry, clean
must be incorporated before freezing.
gravels may also sometimes be found naturally at very
c. Although construction schedules may
low moisture contents in the borrow pit. Dry, crushed or
necessitate the placement of permanent fill or backfill
broken rock may be placed even more effectively under
during or immediately preceding periods of freezing
all temperatures. In one especially urgent situation a
weather, every effort should be made, whenever
compacted fill foundation for a large structure was built in
construction schedules permit, to schedule placement of
mid-winter by the expedient use of a very large inflated
backfill in periods of favorable weather conditions.
shelter into which frozen borrow was trucked, spread in
shallow layers, each of which was TM 5-852-4/AFM 88-
19, Chap. 4 allowed to thaw, then compacted by
6-3
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