Sandy Soils on Wetting, by Jennings and Knight) is used for estimating the
swell potential.
3.
COLLAPSING SOILS
a. Characteristics. Collapsing soils are distinguished by their
potential to undergo large decrease in volume upon increase in moisture
content even without increase in external loads. Examples of soils
exhibiting this behavior are loess, weakly cemented sands and silts where
cementing agent is soluble (e.g., soluble gypsum, halite, etc.) and certain
granite residual soils. A common feature of collapsible soils is the loose
bulky grains held together by capillary stresses. Deposits of collapsible
soils are usually associated with regions of moisture deficiency.
b. Identification and Classification. Detailed geologic studies could
identify potentially collapsible soils. Figure 5 (Reference 19, Research
Related to Soil Problems of the Arid Western United States, by Holtz and
Gibbs) provides guidance for identifying the potential for collapse for
clayey sands and sandy clays found in the western United States. For
cemented soils and nonplastic soils, criteria based on consolidometer tests
are more applicable as illustrated in Figure 6 (Reference 20, A Guide to
Construction on or with Materials Exibiting Additional Settlements Due to
Collapse of Grain Structure, by Jennings and Knight; and Reference 21, The
Origin and Occurrence of Collapsing Soil, by Knight). The potential for
collapse is also evaluated in the field by performing standard plate load
tests (ASTM D1194, Bearing Capacity of Soil for Static Load on Spread
Footings) under varied moisture environments. For further guidance see
Reference 22, Experience with Collapsible Soil in the Southwest, by
Beckwith.
4.
PERMAFROST AND FROST PENETRATION.
a. Characteristics. In non-frost susceptible soil, volume increase is
typically 4% (porosity 40%, water volume increase in turning to ice = 10%,
total heave = 40% x 10% = 4%). In susceptible soil heave is much greater as
water flows to colder zones (forming ice lenses). The associated loss of
support upon thaw can be more detrimental to structures than the heave
itself.
b. Classification. Silts are the most susceptible to frost heave.
Soils of types SM, ML, GM, SC, GC, and CL are classified as having frost
heave potential.
c. Geography. Figure 7 (Reference 23, National Oceanic and Atmospheric
Administration) may be used as a guide for estimating extreme depth of frost
penetration in the United States.
5.
LIMESTONE AND RELATED MATERIALS.
a. Characteristics. Limestone, dolomite, gypsum and anhydrite are
characterized by their solubility and thus the potential for cavity presence
and cavity development. Limestones are defined as those rocks composed of
more than 50% carbonate minerals of which 50% or more consist of calcite
and/or aragonite. Some near shore carbonate sediments (also called
limestone, marl, chalk) could fit this description. Such sediments are
noted for erratic degrees of induration, and thus variability in load
supporting capacity and
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