Geology Reference
In-Depth Information
13
CHAPTER THIRTEEN
CHAPTER THIRTEEN
Field Determination
of Water (Moisture)
Content of Soil
by the Calcium
Carbide Gas
Pressure Tester
Field Determination
of Water (Moisture)
Content of Soil
by the Calcium
Carbide Gas
Pressure Tester
(Referenced Document: ASTM D 4944)
In Chapter 12, the laboratory compaction test was described. Results of
this test give the maximum dry unit weight and optimum moisture content
for a given soil. The maximum dry unit weight is used by designers in spec-
ifying design shear strength, resistance to future settlement, and perme-
ability characteristics of the soil for a given construction site. The soil is
then compacted by field compaction methods to achieve the laboratory
maximum dry unit weight (or a percentage of it as specified in design).
Normally, soil is compacted in the field in layers. After a fill layer
has been compacted by the contractor, it is important that the in-place
dry unit weight of the compacted soil be determined in order to tell
whether the maximum laboratory dry unit weight has been achieved.
There are several methods for determining in-place unit weight, three
of which will be described in the next three chapters. The in-place unit
weight determined by these methods is, however, the wet unit weight of
the soil. To obtain in-place dry unit weight, it is also necessary to find
the moisture content of the soil [for use in Eq. (12-2)].
Moisture content can, of course, be determined by oven drying (see
Chapters 4 and 5); however, such methods may be too time consuming
or inconvenient for field compaction testing, where test results are com-
monly needed quickly. Drying of soil can be accomplished by putting the
sample in a skillet and placing it over the open flame of a camp stove.
(If the soil contains significant organic material, this method should not
INTRODUCTION
189
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