Environmental Engineering Reference
In-Depth Information
2.
Granular soils, including gravel, sand, and silt, are cohesionless materials (except
for apparent cohesion evidenced by partially saturated silt).
3.
Clay soils are cohesive materials.
4.
Organic soils are composed of, or include, organic matter.
Other Groupings
Soils are also placed in general groups as:
1.
Coarse-grained soils including gravel and sand
2.
Fine-grained soils including silt and clay
3.
Cohesive soils, which are clays mixed with granular soils or pure clays
5.3.2
Granular or Cohesionless Soils
Characteristics
General
Boulders and cobbles normally respond to stress as individual units. Gravel, sand, and silt
respond to stress as a mass and are the most significant granular soils.
Particles
Shape is bulky and usually equidimensional, varying from rounded to very angular.
The shape results from abrasion and in some cases solution, and is related to the mode
and distance of transport. Subangular sand grains are illustrated in
Figure 5.8.
Behavior is mass-derived because of pore spaces between individual grains which are
in contact.
Properties
Cohesionless, nonplastic.
FIGURE 5.8
Subangular grains of coarse to medium quartz sand (~14×).
