unfrozen water films around soil particles, larger
The adsorption model; and
unfrozen brine pockets can form during especial-
The osmotic model.
ly rapid ground freezing of saline soils, which also
Although these models differ in the details of the
decreases the mechanical strength of soils (Mahar
mechanisms responsible for frost heaving, there
et al. 1982, Chamberlain 1983).
is general agreement on the factors influencing
Kostetskaya (1977) found that NaCl brines freez-
frost heaving (Miller 1980, Chamberlain 1981,
ing at the eutectic point (21.2C, 5.17 mol kg1;
O'Neill 1983, Perfect et al. 1991). These factors in-
Fig. 2) are sludge ice and have zero strength. How-
clude:
ever, the addition of Na2SO4 to the NaCl brines or
Soil texture (silts are more frost-susceptible
to gravel soils containing the same brines increased
than either sands or clays);
strength. Ogata et al. (1982) found that the com-
Pore size (pore size controls capillary rise, soil
pressive strength for sands, silts and clays gener-
suction and hydraulic conductivity, all of
ally decreased with increasing salinity. An
which are important in the movement of
exception to this generality occurred where soils
water to the freezing front);
were frozen at 32C, where the compressive
Rate of heat removal (there is a maximum rate
strength at 2 and 3% salinity was actually higher
of frost heave at intermediate rates of heat
than at 1% salinity. They attributed this anomaly
removal);
to the fact that 32C was beyond the eutectic tem-
Temperature gradient (this affects the thick-
perature of NaCl. Clearly complex interactions are
ness and hydraulic conductivity of the fro-
possible among specific solutes, freezing and thaw-
zen fringe where ice lensing occurs) (Fig. 3);
ing, and soil physical properties.
Moisture conditions (saturated soils with
high water tables are most susceptible to frost
heaving) and
Frost heaving
From the classical papers of Taber (1929, 1930)
Overburden stress (the greater the overbur-
and Beskow (1935) to more recent reviews (Ander-
den stress, the lower the frost heaving).
son and Morgenstern 1973, Sheeran and Yong 1975,
In general, salts reduce frost heaving (Beskow
Gilpin 1980, Miller 1980, Chamberlain 1981, O'Neill
1935, Kay and Scott 1973, Yong et al. 1973a,b, Shee-
1983, Derjaguin and Churaev 1986, Nakano 1990,
ran and Yong 1975, Chamberlain 1983). Exceptions
Black and Hardenberg 1991, Perfect et al. 1991),
to this generality exists. For example, Beskow
(1935) found that dilute NaCl solutions (≤ 0.05 M*)
frost heaving has been the subject of intense inter-
est because of its importance for engineering in
accelerated frost heaving, but more concentrated
frost-susceptible environments. The stability of
NaCl (0.1 M) as well as CaCl2 (0.0250.5 M) de-
soils for road, railroad, airfield, building, under-
creased frost heaving. Because of the generally
ground storage and pipeline construction in cold
ameliorative effect, solutes have been examined
regions are critically dependent on frost suscepti-
for their ability to reduce frost heaving. Lambe and
bility.
Kaplar (1971) and Lambe et al. (1971) evaluated
Frost heaving is due primarily to the formation
more than 50 additives classified under four func-
tional groups (void fillers and cements, ag-
of segregated ice lenses in soil and only secondari-
gregants, waterproofers, and dispersants) for their
ly to volumetric expansion of water during freez-
ability to modify frost heaving. They found that a
ing (Anderson and Morgenstern 1973, Mageau and
dispersant, tetrasodium pyrophosphate (TSPP),
Morgenstern 1980, Miller 1980, Chamberlain 1981).
and an aggregant, ferric chloride, possessed good
Three conditions must occur simultaneously for
frost heave modifying capabilities. Both additives
frost heaving to occur:
reduced frost susceptibility in soils from "medi-
A prolonged period of subfreezing tempera-
um to high" to "very low to low."
tures;
Sheeran and Yong (1975) have proposed five
Frost-susceptible soils; and
hypotheses to explain the effect of salts on frost
A source of water.
heaving. Salts may affect:
Several models have been proposed to explain frost
The position and temperature of the freezing
heaving (Miller 1980, Chamberlain 1981, O'Neill
front;
1983, Black and Miller 1985, Horiguchi 1987,
The chemical condition of frozen soil;
Nakano 1990, Black and Hardenberg 1991), includ-
The permeability of frozen soil;
ing:
The capillary (or primary) heaving model;
The secondary heaving model;
* M is molarity (mol L1).
6
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