CHAPTER 16
SOILS: SURVEYING AND
EXPLORATION/CLASSIFICATION/FIELD
IDENTIFICATION
In this chapter you will be introduced to the topics
of geological and pedological surveys and will learn
about various methods used for this type of surveying.
Additionally, you will further your knowledge of soils
exploration and you will learn how to classify soils
based on their textural and plasticity-compressibility
characteristics using the Unified Soils Classification
System. Finally, you will learn various field tests that
are useful for expedient soil classification.
Much of the discussion in this chapter assumes that
you are by now knowledgeable of the physical
properties of soils and that you are experienced with
laboratory testing procedures, such as mechanical
analysis and Atterberg limits, that are necessary for
accurate identification and classification of soils.
Should it be necessary, you may find it helpful to review
chapter 15 of the EA3 TRAMAN and chapter 13 in Part
1 of this TRAMAN before beginning your study of this
chapter.
SURVEY SUPPORT FOR GEOLOGY
AND PEDOLOGY
In this section you will be provided a brief
familiarization with the topics of geological and
pedological surveying and mapping. Although these
topics could have been included in a separate discussion
of topographic surveying, they have been included in
this chapter since both are related to soil exploration and
investigation.
GEOLOGICAL SURVEYS
In essence, surveys in support of geology are
topographic surveys; however, you must be aware of the
other specialized data that may be included as required
by the geologist or the soil engineer when you are
collecting data for engineering studies for naval
construction projects.
The end product of most topographic surveys is a
topographic map. In geology or other related sciences,
the topographic survey is the first part of a series of
interrelated surveys. The end product is a map
containing not only topographical information but also
other specialized data keyed to it. In geologic surveys,
a geologist makes systematic observations of the
physical characteristics, distribution, geologic age, and
structure of the rocks as well as the groundwater and
mineral resources that the rocks contain. These
observations are expressed in finished form as geologic
maps and texts. The objective of the geological survey
is to portray, in plan or in cross section, geological data
required for subsequent constructions or for other uses.
Pure geological data has little direct application to
naval problems; however, if the field information is
interpreted into specialized lines, it is of considerable
use in Naval Construction Force (NCF) planning and
operations. NCF requirements may necessitate regional
geological study and mapping, surveys of more limited
areas, or development of detailed geological data at a
construction site.
Methods of Geological Surveying
Most geological data is gathered from an
examination of rocks in the field. In addition,
examination of drainage and relief patterns on detailed
maps or aerial photographs provides considerable
supplementary data on rock structures and distribution.
In the field, the geologist conducts his survey
by examining the rock. He looks to see if it is
exposed at the surface and not covered by soil or
other material. At such exposures, called outcrops,
he systematically records the physical characteristics
of the rock, thickness of exposure, inclination of
the rock, inclination of rock bedding, and develop-
ment of joints or fractures. In addition, he deter-
mines the age of the rock from fossils or the sequence
of rock units. Rock investigations are not confined
to surface exposures, as the deeper seated rocks are
examined by using samples obtained from auger or
boreholes. The information gathered by the geolo-
gist is placed on a map base by plotting the rock types
in color with other data incorporated as symbols
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