4. Significance and Use
4.1 The primary purpose of the unconfined compression test
is to quickly obtain the approximate compressive strength of
soils that possess sufficient cohesion to permit testing in the
unconfined state.
4.2 Samples of soils having slickensided or fissured struc-
ture, samples of some types of loess, very soft clays, dry and
crumbly soils and varved materials, or samples containing
significant portions of silt or sand, or both (all of which usually
exhibit cohesive properties), frequently display higher shear
strengths when tested in accordance with Test Method D 2850.
Also, unsaturated soils will usually exhibit different shear
strengths when tested in accordance with Test Method D 2850.
4.3 If both an undisturbed and a remolded test are per-
formed on the same sample, the sensitivity of the material can
be determined. This method of determining sensitivity is
suitable only for soils that can retain a stable specimen shape
in the remolded state.
N
OTE
2—For soils that will not retain a stable shape, a vane shear test
or Test Method D 2850 can be used to determine sensitivity.
N
OTE
3—The quality of the result produced by this standard is
dependent on the competence of the personnel performing it, and the
suitability of the equipment and facilities used. Agencies that meet the
criteria of Practice D 3740 are generally considered capable of competent
and objective testing/sampling/inspection. Users of this standard are
cautioned that compliance with Practice D 3740 does not in itself ensure
reliable results. Reliable results depend on many factors; Practice D 3740
provides a means of evaluating some of those factors.
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