Geology Reference
In-Depth Information
14
CHAPTER FOURTEEN
CHAPTER FOURTEEN
Determining the
Density and Unit
Weight of Soil in Place
by the Sand-Cone
Method
Determining the
Density and Unit
Weight of Soil in Place
by the Sand-Cone
Method
(Referenced Document: ASTM D 1556)
In certain cases, it is necessary to determine the density and/or unit
weight of a soil either as it exists naturally in the ground or as it may
be compacted in a fill. In the former case, the density of soil in place may
be used to evaluate the comparative strength of the soil; in the latter,
the unit weight may be used to document results of field compaction to
meet contract specifications. The principal use of the in-place soil unit
weight test is in documentation of field compaction.
In Chapter 12 the laboratory compaction test was described. In
practice, representative samples of the soil to be used for fill material
are subjected to the laboratory compaction test to determine the opti-
mum moisture content and maximum dry unit weight. The maximum
dry unit weight is used by designers in specifying design shear strength,
resistance to future settlement, and permeability characteristics. The
fill soil is then compacted mechanically in the field by field compaction
methods to achieve the laboratory maximum dry unit weight. In order
to determine whether the laboratory maximum dry unit weight (or an
acceptable percentage thereof) has been achieved, in-place soil unit
weight tests must be performed in the field on compacted soil.
There are several methods for finding the density/unit weight of
soil in place. This chapter discusses the “sand-cone” method, and
Chapter 15 considers the “rubber-balloon” method. In-place soil density
and unit weight can also be determined with nuclear equipment, utiliz-
ing radioactive materials. This method, which is called “density of
INTRODUCTION
195
Search WWH ::
Custom Search