ASTM D2922-96e1
(Test Method)Standard Test Methods for Density of Soil and Soil-Aggregate in Place by Nuclear Methods (Shallow Depth)
Standard Test Methods for Density of Soil and Soil-Aggregate in Place by Nuclear Methods (Shallow Depth)
SCOPE
1.1 This test method covers the determination of the total or wet density of soil and soil-rock mixtures by the attenuation of gamma radiation where the source and detector(s) remain on the surface (Backscatter Method) or the source or detector is placed at a known depth up to 300 mm (12 in.) while the detector(s) or source remains on the surface (Direct Transmission Method).
1.2 The density in mass per unit volume of the material under test is determined by comparing the detected rate of gamma radiation with previously established calibration data.
1.3 The values tested in SI units are to be regarded as the standard. The inch-pound equivalents may be approximate.
1.4 It is common practice in the engineering profession to concurrently use pounds to represent both a unit of mass (lbm) and a unit of force (lbf). This implicitly combines two separate systems of units; that is, the absolute system and the gravitational system. It is scientifically undesirable to combine the use of two separate sets of inch-pound units within a single standard. This standard has been written using the gravitational system of units when dealing with the inch-pound system. In this system the pound (lbf) represents a unit of force (weight). However, the use of balances or scales recording pounds of mass (lbm), or the recording of density in lbm/ft3 should not be regarded as nonconformance with this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific Hazard statements, see Section 6.
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e1
Designation: D 2922 – 96
Standard Test Methods for
Density of Soil and Soil-Aggregate in Place by Nuclear
Methods (Shallow Depth)
This standard is issued under the fixed designation D 2922; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—Table 1 was corrected editorially in December 1997.
1. Scope mer and 12-in. (305-mm) Drop
D 1557 Test Method for Moisture-Density Relations of Soil
1.1 These test methods cover the determination of the total
and Soil-Aggregate Mixtures Using 10-lb (4.54-kg) Ram-
or wet density of soil and soil-rock mixtures by the attenuation
mer and 18-in. (457-mm) Drop
of gamma radiation where the source and detector(s) remain on
D 2216 Test Method for Laboratory Determination of Water
the surface (Backscatter Method) or the source or detector is
(Moisture) Content of Soil, Rock, and Soil-Aggregate
placed at a known depth up to 300 mm (12 in.) while the
Mixtures
detector(s) or source remains on the surface (Direct Transmis-
D 3017 Test Method for Water Content of Soil and Rock
sion Method).
In-Place by Nuclear Methods (Shallow Depth)
1.2 The density in mass per unit volume of the material
D 4253 Test Method for Maximum Index Density and Unit
under test is determined by comparing the detected rate of
Weight of Soils Using a Vibratory Table
gamma radiation with previously established calibration data.
D 4643 Test Method for Determination of Water Content by
1.3 The values tested in SI units are to be regarded as the
the Microwave Oven Method
standard. The inch-pound equivalents may be approximate.
D 4718 Practice for Correction of Unit Weight and Water
1.4 It is common practice in the engineering profession to
Content for Soils Containing Oversize Particles
concurrently use pounds to represent both a unit of mass (lbm)
D 4944 Test Method for Field Determination of Water
and a unit of force (lbf). This implicitly combines two separate
(Moisture) Content of Soil by the Calcium Carbide Gas
systems of units; that is, the absolute system and the gravita-
Pressure Tester Method
tional system. It is scientifically undesirable to combine the use
D 4959 Test Method for Determination of Water (Moisture)
of two separate sets of inch-pound units within a single
Content by Direct Heating Method
standard. This standard has been written using the gravitational
system of units when dealing with the inch-pound system. In
3. Significance and Use
this system the pound (lbf) represents a unit of force (weight).
3.1 The test methods described are useful as rapid, nonde-
However, the use of balances or scales recording pounds of
structive techniques for the in-place determination of density of
mass (lbm), or the recording of density in lbm/ft should not be
soil and rock.
regarded as nonconformance with this standard.
3.2 The test methods are suitable for quality control and
1.5 This standard does not purport to address all of the
acceptance testing for construction and for research and
safety concerns, if any, associated with its use. It is the
development applications.
responsibility of the user of this standard to establish appro-
3.3 The nondestructive nature of the tests allow repetitive
priate safety and health practices and determine the applica-
measurements to be made at a single test location.
bility of regulatory limitations prior to use. For specific Hazard
statements, see Section 6.
4. Interferences
2. Referenced Documents 4.1 The chemical composition of the sample may affect the
measurement, and adjustments may be necessary.
2.1 ASTM Standards:
4.2 The test methods exhibit spatial bias in that the instru-
D 698 Test Method for Moisture-Density Relations of Soil
ment is more sensitive to the density of the material in close
and Soil-Aggregate Mixtures Using 5.5-lb (2.49-kg) Ram-
proximity to the surface (Backscatter Method only).
These test methods are under the jurisdiction of ASTM Committee D-18 on NOTE 1—The nuclear gauge density measurements are somewhat
Soil and Rock and are the direct responsibility of Subcommittee D18.08 on Special
and Construction Control Tests.
Current edition approved Oct. 10, 1996. Published February 1997. Originally Annual Book of ASTM Standards, Vol 04.08.
published as D 2922 – 71. Last previous edition D 2922 – 91. Annual Book of ASTM Standards, Vol 04.09.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 2922
biased to the surface layers of the soil being tested. This bias has largely
may change the relationship between count rate and material
been corrected out of the direct transmission method and any remaining
density. To offset this aging, the gage may be calibrated as the
bias is insignificant. The backscatter method is still more sensitive to the
ratio of the measured count rate to a count rate made on a
material within the first several inches from the surface.
reference standard or to an air-gap count (for the backscatter
4.3 Oversize rocks or large voids in the source-detector path
air-gap technique, see 9.5.1.3). The reference count rate should
may cause higher or lower density determination. Where lack
be of the same order of magnitude as the measured count rate
of uniformity in the soil due to layering, rock or voids is
over the useful density range of the instrument.
suspected, the test volume site should be dug up and visually
8.2 Standardization of the gage shall be performed at the
examined to determine if the test material is representative of
start of each day’s work, and a permanent record of these data
the full material in general and if rock correction (see 9.6) is
shall be retained. Perform the standardization with the gage
required.
located at least 8 m (25 ft) away from other sources of
4.4 The sample volume is approximately 0.0028 m (0.10
radioactive material, and clear of large masses or other items
3 3 3
ft ) for the Backscatter Method and 0.0057 m (0.20 ft ) for the
which may affect the reference count rate.
Direct Transmission Method when the test depth is 15 cm (6
8.2.1 If recommended by the instrument manufacturer to
in.). The actual sample volume is indeterminate and varies with
provide more stable and consistent results: (1) turn on the
the apparatus and the density of the material. In general, the
gauge prior to use to allow it to stabilize, (2) leave the power
higher the density the smaller the volume.
on during the use of the gage for that day.
8.2.2 Using the reference standard, take at least four repeti-
5. Apparatus
tive readings at the normal measurement period and determine
5.1 Nuclear Gage—An electronic counting instrument, ca-
the mean. If available on the gage, one measurement period of
pable of being seated on the surface of the material under test,
four or more times the normal period is acceptable. This
and which contains:
constitutes one standardization check.
5.1.1 A sealed source of high energy gamma radiation such
8.2.3 If the value obtained above is within the limits stated
as cesium or radium.
below, the gage is considered to be in satisfactory condition,
5.1.2 Gamma Detector—Any type of gamma detector such
and the value may be used to determine the count ratios for the
as a Geiger-Mueller tube(s).
day of use. If the value is outside these limits, allow additional
5.2 Reference Standard—A block of material used for
time for the gage to stabilize, make sure the area is clear of
checking instrument operation and to establish conditions for a
sources of interference, and then conduct another standardiza-
reproducible reference count rate.
tion check. If the second standardization check is within the
5.3 Site Preparation Device—A plate, straightedge, or other
limits, the gage may be used, but if it also fails the test, the
suitable leveling tool which may be used for planning the test
gage shall be adjusted or repaired as recommended by the
site to the required smoothness, and in the Direct Transmission
manufacturer. The limits are as follows:
Method, guiding the drive pin to prepare a perpendicular hole.
5.4 Drive Pin—A pin of slightly larger diameter than the
| N 2 N ||La 2.0 N /F (1)
=
s o o
rod in the Direct Transmission Instrument, used to prepare a
where:
hole in the material under test for inserting the rod.
N = value of current standardization count,
5.5 Drive Pin Extractor—A tool that may be used to remove s
N = average of the past four values of N taken for prior
o s
the drive pin in a vertical direction so that the pin will not
usage, and
distort the hole in the extraction process.
F = value of prescale. [The prescale value (F) is a divisor
5.5.1 A slide hammer, with a drive pin attached, may also be
which reduces the actual value for the purpose of
used both to prepare a hole in the material to be tested and to
display. The manufactor will supply this value if other
extract the pin without distortion to the hole.
than 1.0.] Some instruments may have provisions to
6. Hazards
compute and display these values.
6.1 This equipment utilizes radioactive materials that may 8.2.3.1 If the instrument standardization has not been
be hazardous to the health of the users unless proper precau- checked within the previous three months, perform at least four
tions are taken. Users of this equipment must become familiar new standardization checks, and use the mean as the value for
with applicable safety procedures and government regulations. N .
o
6.2 Effective user instructions together with routine safety
8.3 Use the value of N to determine the count ratios for the
s
procedures, such as source leak tests, recording and evaluation
current day’s use of the instrument. If for any reason the
of film badge data, etc., are a recommended part of the
measured density becomes suspect during the day’s use,
operation and storage of this instrument.
perform another standardization check.
7. Calibration
9. Procedure for Field Use
7.1 Calibration of the instrument will be in accordance with
9.1 Standardize the gage. (See Section 8.)
Annex A1.
9.2 Select a test location. If the gage will be closer than 250
8. Standardization and Reference Check
mm (10 in.) to any vertical mass that might influence the result,
8.1 Nuclear gages are subject to long-term aging of the such as in a trench or alongside a pipe, follow the manufac-
radioactive source, detectors, and electronic systems, which turer’s correction procedure.
D 2922
9.3 Remove all loose and disturbed material. Remove addi- 9.5.2.6 Pull gently on the gage in the direction that will
tional material as necessary to reach the material that repre- bring the side of the probe against the side of the hole that is
sents a valid sample of the zone or stratum to be tested. Surface closest to the detector (or source) location in the gauge
drying and spatial bias should be considered in determining the housing.
depth of material to be removed. 9.5.2.7 Keep all other radioactive sources away from the
gage to avoid affecting the measurement.
9.4 Plane or scrape a smooth horizontal surface so as to
obtain maximum contact between the gage and the material 9.5.2.8 Secure and record one or more readings for the
normal measurement period.
being tested. The placement of the gage on the surface of the
material to be tested is always important, but is especially 9.5.2.9 Determine the ratio of the reading to the standard
count. From this count ratio and the appropriate calibration and
critical to the successful determination of density when using
the backscatter method. The optimum condition in all cases, is adjustment data, determine the in-place wet density.
total contact between the bottom surface of the gauge and the
NOTE 3—Some instruments have built-in provisions to compute the
surface of the material being tested. To correct for surface
ratio, wet density, and to enter an adjustment bias. Additionally some
irregularities, use of native fines or fine sand as a filler may be
instruments may have provisions to measure and compute moisture
necessary. The depth of the filler should not exceed approxi- content, and dry density.
mately 3 mm ( ⁄8 in.) and the total area filled should not exceed
9.6 If the volume tested as defined in 4.4 has excess oversize
10 % of the bottom area of the instrument. The maximum
material with respect to the limitations in the appropriate Test
depth of any void beneath the gage that can be tolerated
Methods D 698, D 1557 or D 4253, then a correction for wet
without filling shall not exceed approximately 3 mm ( ⁄8 in.).
density (unit weight) and water content must be applied. This
Several trial seatings may be required to achieve these condi-
correction will be done in accordance with Practice D 4718.
tions.
This test method requires sampling from the actual test
9.5 Proceed with the test in the following manner:
volume.
9.5.1 Backscatter Procedure:
9.6.1 If samples of the measure material are to be taken for
9.5.1.1 Seat the gage firmly on the prepared test site.
purposes of correlation with other test methods or rock
9.5.1.2 Keep all other radioactive sources away from the
correction, the volume measured can be approximated by a 200
gauge to avoid affecting the measurement so as not to affect the
mm (8 in.) diameter cylinder located directly under the center
readings.
line of the radioactive source and detector(s). The height of the
9.5.1.3 Secure and record one or more readings for the
cylinder to be excavated will be the depth setting of the source
normal measurement period in the backscatter position.
rod when using the Direct Transmission method or approxi-
mately 75 mm (3 in.) when using the Backscatter Method.
NOTE 2—When using the backscatter air-gap procedure, follow the
9.6.2 An alternative to the correction for oversize particles,
instrument manufacturers instructions regarding apparatus set up. Take the
that can be used with mass density methods or minimal
same number of readings for the normal measurement period in the
air-gap position as in the standard backscatter position. Determine the
oversize situations, involves multiple tests. Tests may be taken
air-gap ratio by dividing counts per minute obtained in the air-gap position
at adjacent locations and the results averaged to get a repre-
by counts per minute obtained in standard backscatter position.
sentative value. Comparisons need to be made to evaluate
whether the presence of a single large rock or void in the soil
9.5.1.4 Determ
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