TM 5-818-4/AFM 88-5, Chap. 5
increasing the size of the sample used for water con-
(3) Rubber-balloon method. Procedures and equip-
tent determination with increasing maximum particle
ment for the rubber-balloon method are described in
size. The relations suggested by the American Society
ASTM D 2167. This method utilizes a rubber balloon
for Testing and Materials are shown in the following
attached to a glass or metal cylinder containing water
tabulation:
and having a scale graduated in cubic feet. An annular
device is seated on the prepared ground surface, and
Water content
Minimum test
hole volume
sample
Maximum particle
the balloon apparatus is placed and held down firmly
cu ft
size, in.
on the ring. Then water is forced into the balloon
0.025
100
0.187 (No. 4)
under pressures of 2 to 3 pounds per square inch to ob-
0.050
250
1/2
tain an initial volume measurement to correct for
500
1
0.075
1,000
0.100
ground surface irregularities. The apparatus is re-
2
moved, a small hole is dug, and the apparatus is re-
For significant quantities of larger particles the vol-
placed on the ring. Water is again pumped into the bal-
umes above should be doubled. The accuracy of the test
loon and causes the balloon to conform to the
results is influenced by not only the care taken in pre-
boundary of the hole; then the volume is measured.
paring a test hole but also the degree of recovery of the
This volume less the initial volume is the volume of the
excavated material. A hole with irregular surfaces will
hole. The volumeter apparatus is simple and easy to
cause the volume measurement to be less accurate
operate, and the volume measurement can be made di-
than a hole with smooth surfaces. Thus, the inside of
rectly and in somewhat less time than that with the
the hole should be kept as free of pockets and sharp
sand-cone volume apparatus. The results obtained are
projections as possible. Digging a smooth test hole in
considered to be as accurate as those obtained from the
cohesionless coarse-grained material is particularly
sand-cone apparatus. Like the sand-cone method, the
difficult. In fine-grained soils without gravel particles,
rubber-balloon method can be used to determine the
the hole may be bored with an auger, but hand tools
in-place density of practically all soils except those
will be required to smooth the walls and base of the
containing large quantities of large gravel sizes.
hole and to recover loose material. For coarser-grained
(4) Water-displacement method. Where it is nec-
soils and soils containing a significant amount of grav-
essary to determine the in-place density for a large
el-size particles, hand tools will generally be required
volume of soil, as in coarse-grained soils containing
to excavate the hole to prevent disturbing the material
significant quantities of large gravel sizes, an approx-
in the walls and base of the test hole. Should it become
imate density can be obtained by excavating a large
necessary in digging a test hole in highly compacted
hole (several cubic feet) and determining the volume
material to loosen the material by using a chisel and
by lining the hole with thin plastic sheeting and meas-
hammer, care must be taken not to disturb the soil
uring the quantity of water required to fill the hole. A
around the limits of the hole. All loose particles must
relatively small sample representative of the material
be removed after the final depth has been reached, and
from the excavation is used for determining the water
all particles must be recovered. All soil should be
content. Using the wet and dry weights of the material
placed in a waterproof container as the soil is taken
excavated and the measured volume of the hole, the
from the hole. This measure will prevent loss of water
wet and dry densities of the soil can be determined. Al-
before the soil can be weighed.
though the procedure is not contained in a Military
c. Indirect methods. The indirect methods include
Standard, it is about the only means of determining an
use of the nuclear moisture-density apparatus, Proctor
approximate density for soils with large sizes of gravel
penetrometer, and cone penetrometer. Both the Proc-
or rock.
tor penetrometer and cone penetrometer methods for
b. Size and preparation of test hole. The size of the
determining the density require very careful calibra-
hole and the care used in preparing the test hole for
tion using soils of known density and water content,
the sand volume and balloon methods influence the
and considerable experience in operating the device;
accuracy of the volume measurement. The proper size
even so, the accuracy of these methods may be subject
of the hole is not well established; however, the larger
to question because of the great influence that nonuni-
the hole, the less significant small errors in measure-
formity of water content or a small piece of gravel can
ment of volume become. The instructions in TM
have on the penetration resistance. The Proctor pene-
5-824-2 indicate that a volume of at least 0.05 cubic
trometer may also be used to approximate water con-
foot should be used when testing materials with a
tent of fine-grained soils.
maximum particle size of 1 inch and that larger vol-
(1) Nuclear moisture-density method. Procedures
umes should be used for larger maximum particle
and equipment for the nuclear moisture-density meth-
sizes. ASTM D 1556 suggests certain relations be-
od are described in ASTM D 2922 (for density) and
tween particle size and the test hole volume and
ASTM D 3017 (for water content). The three methods
weight of water content specimen. It also recommends
for determining in-place densities described in ASTM
B-8
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