UFC 3-260-02
30 June 2001
a. Cohesive Soils Containing Negligible Amounts of Gravel. Specimens 35.5 millimeters
(1.4 inches) in diameter are generally satisfactory for testing cohesive soils containing a negligible
amount of gravel, while specimens of larger diameter may be advisable for undisturbed soils having
marked stratification, fissures, or other discontinuities. Depending on the type of sample,
specimens shall be prepared by either of the following procedures:
(1) Trimming Specimens of Cohesive Soil. A sample that is uniform in character and
sufficient in amount to provide a minimum of three specimens is required. For undisturbed soils,
samples about 127 millimeters (5 inches) in diameter are preferred for triaxial tests using
35.5-millimeter-(1.4-inch-) diameter specimens. Specimens shall be prepared in a humid room and
tested as soon as possible thereafter to prevent evaporation of moisture. Extreme care shall be
taken in preparing the specimens to preclude the least possible disturbance to the structure of the
soil. The specimens shall be prepared as follows:
(a) Cut a section of suitable length from the sample. As a rule, the specimens should
be cut with the long axes parallel to the long axis of the sample; any influence of stratification is
commonly disregarded. However, comparative tests can be made, if necessary, to determine the
effects of stratification. When a 127-millimeter- (5-inch-) diameter undisturbed sample is to be
used for 35.5-millimeter- (1.4-inch-) diameter specimens, cut the sample axially into quadrants
using a wire saw or other convenient cutting tool. Use three of the quadrants for specimens; seal
the fourth quadrant in wax and preserve it for a possible check test.
(b) Carefully trim each specimen to the required diameter, using a trimming frame or
similar equipment. Use one side of the trimming frame for preliminary cutting and the other side
for final trimming. Ordinarily, the specimen is trimmed by pressing the wire saw or trimming knife
against the edges of the frame and cutting from top to bottom. In trimming stiff or varved clays,
move the wire saw from the top and bottom toward the middle of the specimen to prevent
breaking off pieces at the ends. Remove any small shells or pebbles encountered during the
trimming operations. Carefully fill voids on the surface of the specimen with remolded soil obtained
from the trimming. Cut specimen to the required length (usually 76 to 89 millimeters (3 to 3-
1/2 inches) for 35.5-millimeter- (1.4-inch-) diameter specimens and 152 to 178 millimeters (6 to
7 inches) for 71-millimeter- (2.8-inch-) diameter specimens) using a miter box.
(c) From the soil trimmings, obtain 200 grams of material for specific gravity and
water content determination.
(d) Weigh the specimen to an accuracy of 0.01 gram for 35.5-millimeter-
(1.4-inch-) diameter specimens and 0.1 grams for 71-millimeter- (2.8-inch-) diameter specimens.
(e) Measure the height and diameter of the specimen to an accuracy of
0.25 millimeters (0.01 inch). Specimen dimensions based on measurements of the trimming
frame guides and miter box length are not sufficiently accurate. The average height Ho of the
specimen should be determined from at least four measurements, while the average diameter
should be determined from measurements at the top, center, and bottom of the specimen, as
follows:
%
%
(L-1)
L-2
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