Triaxial Compression Test - Soil Properties: Testing, Measurement, and Evaluation - page 341

Note 1 —If oversize particles are found in the specimen after
testing, a particle-size analysis may be performed in accor-
dance with ASTM Test Method D 422 to confirm the visual
observation and the results provided with the test report.
(2) Undisturbed Specimens —Prepare undisturbed specimens
from large undisturbed samples or from samples secured in ac-
cordance with ASTM Practice D 1587 or other acceptable undis-
turbed tube sampling procedures. Samples shall be preserved
and transported in accordance with the practices for Group C
samples in ASTM Practices D 4220. Specimens obtained by tube
sampling may be tested without trimming except for cutting the
end surfaces plane and perpendicular to the longitudinal axis of
the specimen, provided soil characteristics are such that no sig-
nificant disturbance results from sampling. Handle specimens
carefully to minimize disturbance, changes in cross section, or
change in water content. If compression or any type of noticeable
disturbance would be caused by the extrusion device, split the
sample tube lengthwise or cut the tube in suitable sections to fa-
cilitate removal of the specimen with minimum disturbance. Pre-
pare trimmed specimens in an environment such as a controlled
high-humidity room where soil water content change is mini-
mized. Where removal of pebbles or crumbling resulting from
trimming causes voids on the surface of the specimen, carefully
fill the voids with remolded soil obtained from the trimmings.
When the sample condition permits, a vertical trimming lathe
may be used to reduce the specimen to the required diameter. Af-
ter obtaining the required diameter, place the specimen in a
miter box and cut the specimen to the final height with a wire
saw or other suitable device. Trim the surfaces with the steel
straightedge. Perform one or more water content determinations
on material trimmed from the specimen in accordance with
ASTM Test Method D 2216. Determine the mass and dimensions
of the specimen. A minimum of three height measurements (120°
apart) and at least three diameter measurements at the quarter
points of the height shall be made to determine the average
height and diameter of the specimen.
(3) Compacted Specimens —Soil required for compacted specimens
shall be thoroughly mixed with sufficient water to produce the
desired water content. If water is added to the soil, store the mate-
rial in a covered container for at least 16 h prior to compaction.
Compacted specimens may be prepared by compacting material
in at least six layers using a split mold of circular cross section
having dimensions meeting the requirements enumerated in
(1). Specimens may be compacted to the desired density by either:
(1) kneading or tamping each layer until the accumulative mass of
the soil placed in the mold is compacted to a known volume; or
(2) by adjusting the number of layers, the number of tamps
per layer, and the force per tamp. The top of each layer shall be