Geoscience Reference
In-Depth Information
here a few mutual relationships: for
P
= 0.4,
e
= 0.67; for
P
= 0.45,
e
= 0.82; for
P
= 0.5,
e
= 1; for
P
= 0.55,
e
= 1.22; etc. In well-graded dense sand,
e
= 0.45 (related
to
P
= 0.31); in loess frequently in ranges
e
= 0.85 to
e
= 0.92 (
P
= 0.46 to
P
= 0.48);
and in the top A horizon of the majority soils, we fi nd
e
in ranges between 1.0 and
1.25 (
P
between 0.5 and 0.55).
Soil pores can be demonstrated or modeled in various levels of approximation.
An oversimplifi ed arrangement consists of spherical particles having the same size,
i.e., the same radius. With each particle contacting a neighboring particle at only
one point, the particles can be arranged in one of three models (Fig.
7.1
).
The loosest arrangement is the cubic model. When we connect the centers of
neighboring spheres in such a model, we obtain a cube with each particle having six
contact points with its neighbors. When we connect the centers in a two-dimensional
Fig. 7.1
Spherical soil particle models of pores: cubic packing with porosity
P
= 48 % (
top left
)
and rhombohedral packing with
P
= 26 % (
top right
). Rhombohedral packing of more realistic soil
particles of roughly uniform size (
bottom
)
