6.
QUICK CLAYS.
a. Characteristics. Quick clays are characterized by their great
sensitivity or strength reduction upon disturbance.
All quick clays are of marine origin. Because of their brittle
nature, collapse occurs at relatively small strains. Slopes in quick clays
can fail without large movements. For further guidance see Reference 5 and
Reference 26, Quick Clays and California: No Quick Solutions, by Anne.
b. Identification. Quick clays are readily recognized by measured
sensitivities greater than about 15 and by the distinctive, strain-softening
shape of their stress-strain curves from strength or compressibility tests.
7.
OTHER MATERIALS AND CONSIDERATIONS.
a. Man-Made Fills. Composition and density are the main concerns.
Unless these can be shown to be non-detrimental to the performance of the
foundation, bypassing with deep foundations, or removal and replacement are
in order.
Sanitary landfills may undergo large settlements under self weight
as well as under structural loads. Guidelines on the evaluation of
settlement and other foundation considerations for sanitary landfills are
given in DM-7.3, Chapter 3.
b. Chemically Reactive Soils. For foundation construction, the main
concerns usually are corrosion and gas generation. Corrosion potential is
determined in terms of pH, resistivity, stray current activity, groundwater
position, chemical analysis, etc.; and a compatible foundation treatment,
e.g., sulfate resistant concrete, lacquers, creosote, cathodic protection,
etc., is prescribed. For gas concentration, organic matter content and
field testing for gas are usually performed. If gas generation is expected,
some form of venting system is designed (see Chapter 2). The potential
presence of noxious or explosive gases should be considered during the
construction excavations and tunneling.
c. Lateritic Soils. Lateritic soils are found in tropical climates
throughout the world. Typical characteristics are shown in Table 12. For
further guidance see Reference 27, Laterite Soil Engineering, by Gidigasu;
Reference 28, Laterite Genesis, Location, Use, by Persons; Reference 29,
Engineering Study of Laterite and Lateritic Soils in Connection with
Construction of Roads, Highways and Airfields, by the U.S. Agency for
International Development; Reference 30, Laterite, Lateritic Soils and Other
Problem Soils of Africa, by the U.S. Agency for International Development;
and Reference 31, Laterite and Lateritic Soils and Other Problem Soils of
the Tropics, by the U.S. Agency for International Development.
d. Submarine Soils. Typical characteristics are shown in Table 12.
Further guidance may be found in Reference 32, Engineering Properties of
Submarine Soils: State-of-the-Art Review, by Noorany and Gizienski.
7.1-44
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