Page 306 - Geotechnical Engineering Soil and Foundation Principles and Practice

Compaction
Compaction 301

Figure 13.17
Some
representative
tests showing the
influence of
gradation on
compacted density
(Johnson and
Sahlberg, 1962).

that the lowest density is obtained with a sand that is nearly all one size, which is
the reason such a soil is said to be poorly graded and classified as SP or A-3.

13.11 FIELD DENSITY TESTS

13.11.1 Density as a Means for Compaction Control
Measurements of soil density and moisture content are the primary means for
quality control of compaction. In-place density measurements also are used for
determining cut-and-fill quantities. For example, if the density of soil in a borrow
pit will be increased 15 percent as a result of compaction operations, this
15 percent reduction in volume (which is loosely termed ‘‘shrinkage’’) must be
taken into account when calculating borrow quantities.

13.11.2 Direct Measurement Methods
The classic methods for measuring compacted density involve hand-excavating a
hole and measuring the volume of the hole, and the weight and moisture content
of the soil taken from the hole. The volume of the hole is determined by expanding
a rubber balloon into the hole with water and measuring the volume of water
required (a volumeter test), or by filling the hole with a standard sand and
measuring the amount of sand required (a sand-cone test). Construction traffic
must be halted during sand-cone tests because vibrations affect packing of the

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