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example, in Fig.
7.6
. Even more important is the fact that the pore-size distribution
in real soils is close to the ideal shape in Fig.
7.6
, and this “bell” shape is well
described using mathematical statistics. If we had used a linear scale where the
distance between 0 and 10 is the same as between 100 and 110, then the peak of the
pore-size distribution curve would be shifted to the left making differences between
the two curves that we present next in Fig.
7.7
less distinct.
A graph of pore-size distribution within a structured soil is more complicated. Its
curve plotted with logarithmic scale on the horizontal axis looks like a Bactrian
camel with its characteristic double humps. The pore-size distribution curve of a
structured soil also has two humps - one representing pores mainly between the
aggregates and the second of fi ner pores residing inside aggregates and between
Fig. 7.7
Pore-size distributions in two aggregated soils before and after compaction by an applied
pressure of 300 kPa. Before compaction, the most frequent pores between the small aggregates of
the loamy sand have a radius of about 20
m, while those between the aggregates in the clay loam
are more than twice as large with a radius of 55
μ
m. The radius of the most prevalent pores between
the particles inside the aggregates of the loamy sand is 2.5
μ
μ
m, while that of the clay loam is three
times smaller, i.e.,
r
= 0.8
m. The broken curves for each soil manifest signifi cant changes of rela-
tive pore sizes after a long-time compression with 300 kPa
μ
