Mats were made of oak and were placed using
Laboratory CBR tests
loaders or the HEMTT crane.
Ten soil samples were taken and sent to
CRREL's Soils Laboratory for CBR testing (CBR
PVC fascine
tests are an index of soil bearing capacity). Com-
A fascine was built from schedule 80 PVC pipes
paction tests were conducted using ASTM Stan-
by linking the pipes together with 0.95-cm-(3/8-
dard D 698, Method C, and CBR tests were con-
in.-) diameter cable. (Metal pipes or schedule 40
ducted using ASTM Standard D 1883 (ASTM 1985).
PVC with a thinner cable can also be used.) The
Test procedures are outlined and results discussed
fascine was constructed on site, and was used to
in Appendix B.
fill low-lying areas while still maintaining drain-
Dynamic cone penetrometer (DCP)
age though the pipes. One fascine mat was cov-
The DCP is a sturdy, portable device that can
ered with tire mats in an area where it filled a
penetrate soil layers with CBRs ranging from less
small stream, and another was used with geotextile
than 1 to greater than 100 (Webster et al. 1992).
and chunkwood where the trail turned a corner
Shown in Appendix B (Fig. B5a), it consists of a
adjacent to a swamp.
16-mm- (0.625-in.-) diam. steel rod with a 60 cone
of base diameter 20 mm (0.790 in.) attached to one
Control
end. The cone is driven into the ground by a
Each test area had one or more control sections
sliding hammer, and penetration and correspond-
of bare ground with no stabilization treatment.
ing blow count are recorded until resistance, or a
Gravel or other materials were brought in if
desired depth, is obtained.
"NOGO" situations were encountered.
The DCP readings are correlated to CBR
strength values by the equation
SITE CHARACTERIZATION
CBR = 2.46 1.12 log DCP
TESTING
Table 4 summarizes soil tests conducted and
as determined by the Waterways Experiment Sta-
terrain properties measured on the wooded trail,
tion (WES) (Webster et al. 1992). The WES data-
sloped trail, and pentagonal loop trail. Typical
base was based upon a variety of soil types.
data record sheets are shown in Appendix F. Each
Clegg impact tester (CIT)
of the three trails will be described in detail fol-
The CIT (Fig. B5b) provides another means of
lowing a brief description of testing and sam-
obtaining field CBR values. It is a modified labo-
pling.
ratory compaction hammer fitted with a piezo-
Detailed photographic and visual observations
electric accelerometer (Clegg 1978). The output is
were included as part of both site characterization
provided by an electronic readout. Peak decelera-
and performance testing.
Table 4. Site characterization activities.
Activity or test device
To determine or measure
Clegg impact tester (CIT)
California bearing ratio (CBR) (hardness)
Dynamic cone penetrometer (DCP)
CBR
Static cone
Stiffness--cone index
Laboratory CBR test
CBR
Vitel radio frequency moisture sensors
Volumetric moisture contents
Gravimetric moisture samples
Gravimetric moisture contents
Nuclear moisture density gauge--densimeter
Density and gravimetric moisture
Thaw depth probe and soil temperature
Depth to resistance and corresponding temperature
Drive cylinders
Density/water content
Preconstruction rut depth measurements
Rut depths
Surface elevation survey
Centerline profile
Bagged samples for laboratory testing
CBR and gradation.
General site characterization evaluations
General characterization of site
(e.g., % surface water, drainage, vegetation, etc.)
5
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