Soil Properties: Shrink/Swell Potential

A soil survey contains maps
and a description of each
major soil in the survey area.
More important, the survey
describes how soil properties
affect a wide range of rural
and urban land uses. One of
these properties, shrink/swell
potential, is of great importance
in the construction industry.

Shrink/swell potential is the
relative change in volume to
be expected with changes in
moisture content, that is, the
 extent to which the soil shrinks
as it dries out or swells when
 it gets wet.
Extent of shrinking and swelling
is influenced by the amount and
kind of clay in the soil.
 Shrinking and swelling of soils
causes much damage to
building foundations, roads and other
 structures.
 A high shrink/swell potential indicates
a hazard to maintenance of structures
 built in, on, or with material having this rating.
Moderate and low ratings lessen the hazard accordingly.

As you can see by the map on the right, produced by the Az dept. of Agriculture,
 Expansive soils run in pockets
 throughout the Metroplolitan Phoenix area.