TM 5-852-4/AFM 88-19, Chap. 4
Slurry soil
Type of pile
Silt
Sand
Steel
1.0
1.5
Concrete
1.5
1.5
Wood, untreated or lightly
creosoted
1.5
1.5
Wood, medium creosoted
(no surface film)
1.0
1.5
Wood, coal tar-treated
(heavily coated)
0.8
0.8
Notes:
1. Applies only for soil temperatures down to about 25
F.
2. Where factor is the same for silt and sand, the
surface coating on the pile controls, regardless of type of
slurry. In the remaining factors the pile is capable of
generating sufficient bond so that the slurry material
controls.
3. Gradations typical of soils used for slurry backfill are
shown in Figure 2-11 as follows:
Silt - SFS, Fairbanks silt
Sand - SM, McNamara concrete sand
4. Pile load tests performed using 10 kips/day load
increment were adjusted to 10 kips/3 day increment to
obtain curves shown.
5. Clays and highly organic soils should be expected to
have lower adfreeze bond strengths.
Correction factors for type of pile and slurry backfill
(using steel in slurry of low-organic silt as 1.0)
U. S. Army Corps of Engineers
Figure 4-82. Tangential adfreeze bond strengths vs. temperature for silt-water slurried 8.625-inches-O.D.
steel pipe piles in permafrost averaged over 18 to 21 feet embedded lengths in permafrost134.
below freezing when load is increased relatively rapidly to
behavior is considered the most nearly analogous
failure, but most frozen soils exceed the strength of ice at
characteristic. Also, as illustrated by figure 2-15, hard,
lower temperatures. At a temperature of about 30 F,
sound freshwater ice shows a lower rate of creep
freshwater ice, frozen concrete sand and fine sand have
deformation than frozen soils, at least in the temperature
shear strengths of about the same magnitude, but frozen
range above about 26 F; data are not available for lower
silt is significantly weaker. With lowering of temperature,
temperatures, or for lower temperatures, or for ice which
ice does not gain further shear strength, but the frozen
is porous or contains significant amounts of impurities.
soils do. At temperatures between 30 and 25 F, shear
However, the much more rapid rates of freezeback
obtainable with minimum moisture content slurries offer
strength of sands may exceed that of silt by 33 percent
134
a significant construction advantage . Concrete sand
to more than 100 percent. At a temperature of about
also will usually contain few soluble materials to alter
20F sands and silt may have about equal shear
freezing temperature of the pore water.
strengths, but these may exceed the shear strength of
ice substantially. As temperatures fall below 200F, silt
(i) The use of steel H-type piles or
other irregular section piles, which have considerably
continues to increase in shear strength at a rate which is
more surface area than a comparable-size circular pile,
much more rapid than for sand. In absence of reliable
will not result in
direct adfreeze bond strength data, shear strength
4-134
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