Number of Applications
material is used under in-situ conditions. Under
Damage =
(1)
saturated moisture conditions, the amount of
Ndesign
frost heave and frost depth is approximately the
where Number of Applications is the design appli-
same for all of the computer simulations. This
cations, where Ndesign for the bottom of the pave-
may be the case if the pavement layer is cracked
ment is calculated using
and water and fine material are allowed to flow
into the base/subbase layer and the pavement
Ndesign = 0.0685(Strainhorizontal )-5.671 (Mr )-2.363 (2)
structure should become fully saturated.
One of the problems with the FROST model is
where Ndesign = the number of calculated appli-
that it is unable to account for drainage during
cations
the frost heave process. Materials that have a low
Strainhorizontal = the calculated tensile strain
amount of fines passing the 0.074-mm sieve will
Mr = modulus value of the material
drain and have less suction to draw water toward
(psi).
the freezing front.
To further study the effect of increasing the
Ndesign for the top of the subgrade is calculated
base course layer to 560 mm, the simulations
using
were run again, and the water table was placed at
a depth of 940 mm below the surface of the pave-
Ndesign = 1.94 10-7 (Strainvertical )-4.0
(3)
ment for both the structure using 640 mm of Til-
where Strainvertical is the calculated compressive
con fill and the structure using 560 mm of graded
strain.
aggregate base (Fig. 7 and 9). The results from
Damage calculations were only performed on
these simulations showed no frost heave occur-
the 560-mm base course pavement structure,
ring in the 560-mm graded aggregate base course
since this structure is representative of the speci-
structure.
fied design. It should be noted that only the struc-
ture simulating moist (not saturated conditions)
CUMULATIVE DAMAGE
was investigated.
Estimated damage is calculated on a daily
Pavement structures will degrade over time
basis and summed for a 1-year period to obtain a
due to frost heave and thaw weakening, and the
anticipated loading from traffic. A damage model
total estimate of damage to the pavement struc-
ture (otherwise known as Miner's rule). Using
can be used to predict the rate of this degradation.
this, failure occurs when Damage equals or ex-
The pavement design specifications proposed for
ceeds 1.0. Therefore, for a section to last its design
the Raymark Superfund site for heavy-duty traf-
life, the value of the calculated damage value
fic was based on a design life of 20 years, and esti-
should not accumulate to 1.0 until the design
mating an equivalent axle load (EAL) between 7.0
and 46.0 per day. The CRREL SLED model (Sea-
period expires. Damage was calculated based on
both 7 and 46 EALs per day. The estimated
sonal Layered Elastic Design) was used to create
amount of cumulative damage calculated in the
a multilayered pavement structure, which esti-
first year using 46 EALs per day was 0.0076 at the
mated strain values at the bottom of the pave-
bottom of the pavement and 0.001 at the top of
ment layer and the top of the subgrade layer.
the subgrade (Fig. 20 and 21). Based on a linear
SLED is composed of four computer programs.
summation of daily damage, the results suggest
The first program is FROST, which estimates frost
that the pavement structure will not fail from
heave and frost depths. TRANSFRM uses the daily
either fatigue nor subgrade rutting during its
output from FROST to produce output files of lay-
design life. Results of the damage calculations are
ered pavement systems with estimated modulus
given in Appendix H in Internal Report 1179.
values. The output files from TRANSFRM are
used as input into NELAPAV (Nonlinear Elastic
Layer Analysis for PAVements), which calculates
CONCLUSIONS
the strains within a layered pavement system
Laboratory frost heave tests indicate that the
(Irwin and Speck 1986). Finally, damage estima-
Tilcon common granular fill may be classified as
tions were calculated using the Shell damage
model (Huang 1993). The Shell damage model
of low to medium frost-susceptibility. However,
uses the following equations:
if the material becomes saturated, the tests indi-
cate that the material is highly frost-susceptible.
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