Geology Reference
In-Depth Information
A field test was conducted to determine soil densities by the nuclear
method. The following direct readings from a nuclear density device
were obtained:
NUMERICAL
EXAMPLE
Test
Wet
Moisture
Dry
Test
Depth
Unit Weight
Content
Unit Weight
(lb/ft
3
)
(lb/ft
3
)
No.
(in.)
(%)
1
8
124.9
9.6
114.0
2
8
126.9
8.4
117.1
3
8
122.3
10.1
111.1
4
8
124.2
9.8
113.1
5
8
126.3
8.4
116.5
6
8
128.2
8.2
118.5
Additionally, the following information was known from a previous
laboratory compaction test:
Max. Lab.
Optimum
Test
Dry Unit Weight
Moisture Content
(lb/ft
3
)
No.
(%)
1
119.6
8.9
2
119.6
8.9
3
120.5
8.8
4
120.5
8.8
5
121.5
8.3
6
121.5
8.3
The specified minimum compaction is
95.0
percent for each test. The
percent compaction for each test is determined by dividing the dry unit
weight, as determined by the nuclear density device, by the maximum
laboratory dry unit weight. For example, for test no. 1, the percent com-
paction is
114.0/119.6
0.953, or 95.3 percent. This value is compared
to the specified minimum compaction to see if the compaction effort
is satisfactory. In this example, a specified minimum compaction of
95.0
percent was indicated; hence, this particular compaction effort (i.e.,
test no. 1) is acceptable. The remaining tests (nos. 2 through 6) are
treated in the same manner.
All data are presented on the form shown on page 237. (At the end of the
chapter, two blank copies of this form are included for the reader's use.)
The nuclear method is considerably faster to perform than the sand-
cone and rubber-balloon methods. It has the disadvantage, however, of
potential hazards to individuals handling radioactive materials. The
nuclear apparatus is also considerably more costly than the appara-
tuses used in the other two methods. Additionally, certain soil types
(e.g., micaceous ones) may not yield accurate results by the nuclear
method.
Recall that Chapters 12 through 16 are all used in an overall com-
paction operation. Chapter 12 describes the laboratory compaction test,
SUMMARY
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