Determining the Unconfined Compressive Strength of Cohesive Soil - Soil Properties: Testing, Measurement, and Evaluation - page 323

(1) Specimen Size —Specimens shall have a minimum diameter of
30 mm (1.3 in.), and the largest particle contained within the test
specimen shall be smaller than one tenth of the specimen diameter.
For specimens having a diameter of 72 mm (2.8 in.) or larger, the
largest particle size shall be smaller than one sixth of the specimen
diameter. If, after completion of a test on an intact specimen, it is
found, based on visual observation, that larger particles than per-
mitted are present, indicate this information in the remarks sec-
tion of the report of test data (Note 1). The height-to-diameter ratio
shall be between 2 and 2.5. Determine the average height and di-
ameter of the test specimen using the dial comparator. Take a min-
imum of three height measurements (120° apart), and at least
three diameter measurements at the quarter points of the height.

PREPARATION
OF TEST
SPECIMENS [1]

Note 1 —If large soil particles are found in the sample after
testing, a particle-size analysis performed in accordance with
ASTM Method D 6913 may be performed to confirm the visual
observation and the results provided with the test report.

(2) Intact Specimens —Prepare intact specimens from large samples
or from samples secured in accordance with ASTM Method D 1587
and preserved and transported in accordance with the practices for
Group C samples in ASTM Method D 4220. Tube specimens may be
tested without trimming except for the squaring of ends, if condi-
tions of the sample justify this procedure. Handle specimens care-
fully to reduce the potential for additional disturbance, changes in
cross section, or loss of water content. If compression or any type of
noticeable disturbance would be caused by the extrusion device,
split the sample tube lengthwise or cut it off in small sections to fa-
cilitate removal of the specimen without disturbance. Prepare
carved specimens with minimal disturbance and, whenever possi-
ble, in a humidity-controlled room. Make every effort to prevent
any change in water content of the soil. Specimens shall be of uni-
form circular cross section with ends perpendicular to the longitu-
dinal axis of the specimen. When carving or trimming, remove any
small pebbles or shells encountered. Carefully fill voids on the
surface of the specimen with remolded soil obtained from the trim-
mings. When pebbles or crumbling result in excessive irregularity
at the ends, cap the specimen with a minimum thickness of plaster
of paris, hydrostone, or similar material. When sample condition
permits, a vertical lathe that will accommodate the total sample
may be used as an aid in carving the specimen to the required
diameter. Where prevention of the development of appreciable cap-
illary forces is deemed important, seal the specimen with a rubber
membrane, thin plastic coatings, or with a coating of grease or
sprayed plastic immediately after preparation and during the entire
testing cycle. Determine the mass and dimensions of the test speci-
men. If the specimen is to be capped, its mass and dimensions should
be determined before capping. If the entire test specimen is not to be
used for determination of water content, secure a representative