Lesson 2/Learning Event 3
the friction between the surfaces of the particles to help hold them in place. In an angular material, the
friction is increased by the roughness of the surface and the area of contact. In action, an interlocking
action is developed between the angular particles which gives a much greater stability than friction
alone.
UNDISTURBED SOIL PROPERTIES
A complete description of a soil includes prominent characteristics of the undisturbed materials. The
aggregate properties of sand and gravel are described qualitatively by the terms loose, medium, and
dense, while those of clays are described by hard, stiff, medium, and soft. These characteristics usually
are evaluated on the basis of several factors, including the relative ease or difficulty of advancing the
drilling and sampling tools and the consistency of the samples. In soils that are described as soft, it
should also be indicated whether the material is loose and compressible, as in an area under cultivation,
or spongy or elastic, as in highly organic soils. (Moisture conditions will influence these characteristics
and should be included in the report.)
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