tion of the hammer upon impact has been shown
creases appreciably as water content increases.
to be a useful soil strength indicator, and regres-
Volumetric moisture is then determined by the
sion analysis has shown good agreement with
Vitel probe's built-in calibration curves for spe-
CBR (Alkire and Winters 1986). The CIT provides
cific soil types, e.g., sand, silt, and clay.
a low-cost method for obtaining near-surface
strength data, and is generally used for low-cost,
Gravimetric moisture samples
low-volume roads.
Testing for gravimetric moisture was conducted
in accord with ASTM Standard D 2216 (ASTM
1985). Small soil samples were collected in mois-
Static cone penetrometer
The static cone penetrometer is a small por-
ture tins, weighed wet, oven dried, weighed dry,
table soil testing device used by military personnel
and the moisture contents were determined.
to measure shear resistance as a means for evalu-
ating trafficability (U.S. Army and Air Force 1968).
Drive cylinders
It consists of a 30, 1.3-cm (0.505-in.) diam. cone
A drive cylinder is a hollow metal tube that is
tip on a 16-mm- (0.625-in.-) diam. rod, a proving
driven into the ground to extract an undisturbed
ring, a micrometer dial, and handle. The rod is
soil sample. The sample weight and the known
held vertically, and a slow but steady downward
sample volume allow in-situ soil density to be
force is applied. Proving ring deformation is pro-
determined.
portional to the amount of force required to move
the cone downward through the soil. The amount
Nuclear moisture density
of force, considered to be an index of the soil's
gauge/densimeter
strength, is indicated by the dial inside the prov-
This device, which operates by emitting low
ing ring. The value determined from this reading
level radiation, was used to determine both mois-
is called the cone index (CI). Readings are typi-
ture content and density of the surface and near-
cally recorded at 2.5-cm (1-in.) intervals. Addi-
surface soil.
tional penetration tests were conducted in remold-
ing cylinders in the laboratory to assess the effect
Thaw depth probe
of repeated loads on penetration resistance. The
A metal rod approximately 900 mm (35 in.) in
procedure is outlined and discussed in Appendix
length and 6.35 mm (0.25 in.) in diameter was
B. Site specific results for this and other tests are
used to determine thaw depth. The metal probe
shown in Appendix A.
was simply pushed into the ground until it met
resistance. A thermocouple at the tip of a second
762-mm- (30-in.-) long probe aided in determin-
Vitel radio frequency (RF)
ing whether resistance was provided by a frozen
moisture probe
layer, i.e., approximately 0C (32F), or simply a
RF probes determine a soil's volumetric mois-
ture content by measuring the soil's dielectric con-
hard material, such as bedrock or even a large
stant (Vitel 1994). RF probes (and time domain
stone (probably some temperature above approxi-
mately 0C [32F]).
reflectometry [TDR] probes that operate on the
same principle) are gaining rapid acceptance in
the United States as a method for monitoring soil
Surface elevation surveys and
moisture content in pavement systems. The RF
preconstruction rut depths
probe consists of a probe head, four sensing tines,
Trail surface elevation surveys were conducted
and a multiconductor cable to connect to a re-
using an engineer's level and rod. The result was
cording device. While RF probes are generally
a centerline profile for each of the three trails. Pre-
permanently installed at several depths beneath a
construction rut depths were also measured and
pavement surface to monitor moisture content as
recorded. "Rut depth" for this evaluation is de-
a function of time, a portable probe was used to
fined as the rut's maximum depth relative to the
measure near-surface moisture content for this
tangent of its bounding windrows.
project.
The dielectric constants of the three major con-
Site characterization forms
stituents of moist (unfrozen) soil, e.g., soil par-
Site characterization forms were developed to
ticles, air, and water, are approximately 4, 1, and
record a variety of site characteristics that may
80, respectively. It follows that the capacitance
not necessarily be reflected by discrete measure-
response, a function of the dielectric constant, in-
ments listed above. Information recorded on site
6
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