TM 5-818-4/AFM 88-5, Chap. 5
plete records of the procedures and tests, and then by
not contained in the specifications, the field engineers
studying and evaluating these records, a procedure to
and inspection personnel should provide maximum
use on the job can be established. In addition to water
guidance to the contractor to aid him in establishing
content and density check tests, undisturbed samples
adequate processing, placement, and compaction pro-
should be obtained to determine that the shear and
cedures. To meet this problem the contractor must be
consolidation characteristics are consistent with de-
provided with suggested improvements of equipment
sign requirements. Once control for field conditions
type, if they have not been specified, and procedures
has been established, the backfill can proceed at a nor-
during the initial stages of backfill operations. The es-
mal rate. The contractor should be required to adhere
tablishment of the procedures and equipment type
that will produce adequate compaction of the backfill
to the established processing, placement, and compac-
material must be supported by a comprehensive pro-
tion procedures.
gram of control testing.
c. If provisions for construction of a test section are
Section B-3. FIELD MOISTURE-DENSITY TEST METHODS
B-6. General. Field density measurements of the
should be used as the standard test by which indirect
test results are correlated with density. Other direct
compacted backfill are essential to ensure that backfill
methods are the drive-cylinder method, rubber-balloon
meets the required design densities necessary for the
method, and water-displacement method.
proper functioning of the structure within that back-
(1) Sand-cone method. Procedures and equipment
fill. Although water content requirements are not gen-
for the sand-cone method are described in MIL-
erally specified in military specifications, the measure-
STD-621A (Method 106) and ASTM D 1556. The pro-
ment and control of water content is important in ob-
cedure as described in the references involves prepara-
taining required densities. The four density measure-
tion of the ground surface, measurement of an initial
ment test methods used for the Corps record and con-
volume for the purpose of correcting for surface ir-
tract acceptance enforcement are listed below.
regularities, and measurement of a second volume
a. The sand-cone method as described in MlL-
after a small hole is dug. The difference in the volumes
STD-621A (Method 106) and ASTM D 1556.
is the volume of the hole. The sand used is a standard
sand (Ottawa or other sands having rounded grains
D 2167.
and a uniform gradation) that has been calibrated for
c. The nuclear moisture-density method as de-
weight versus volume occupied when falling from a
scribed in ASTM D 2922 (for density) and ASTM D
standard, constant height. The weight of sand used is
3017 (for water content).
measured by weighing the sand density cylinder be-
fore and after each volume measurement, and the
d. The drive-cylinder method as described in
volume is determined from the weight versus volume
MIL-STD-621A (Method 102) and ASTM D 2937 for
calibration. The soil removed from the hole is weighed,
soft, fine-grained cohesive soils. The water-displace-
the water content determined (MIL-STD-621A), and
ment method described in EM 1110-2-1911, although
the dry weight computed. The wet density and dry
not currently used for Corps contract enforcement,
density of the soil are computed by dividing the appro-
may be used for supplementary density testing for
priate weights by the computed volume. The sand-cone
rocky materials. Rapid field methods of determining
method can be used to determine the in-place density
or approximating water content-density are also dis-
of practically all soils except those containing large
cussed in the following paragraphs.
quantities of large gravel sizes.
B-7. Water content and density test
(2) Drive-cylinder method. Procedures and equip-
methods. Field density can be determined by direct
ment for the drive cylinder method are described in de-
or indirect methods. In the direct methods, the weight
tail in MIL-STD-621A (Method 102) and ASTM D
of soil removed from a hole and the volume of the hole
2937. The procedure consists of driving a 3-inch-diam-
are determined and used to compute the density. In
eter by 3-inch-high sampling tube of known volume
the indirect methods, a characteristic of the soil, such
into the soil, excavating the sampling tube and soil,
as radiation scattering or penetration resistance, is
and trimming off the soil protruding from the ends of
measured with an instrument such as a nuclear densi-
the tube. The weight and water content of the soil are
ty meter or penetrometer, and then a previously deter-
measured and the dry weight is computed. The wet
mined relation between density and the characteristic
density and dry density of the soil are computed by
measured is used to determine the density.
dividing the appropriate weights by the computed
a. Direct methods. The sand-displacement method
volume. The drive-cylinder method is limited to moist,
is considered to be the most reliable direct method and
fine-grained cohesive soils.
B-7
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