Triaxial Compression Test - Soil Properties: Testing, Measurement, and Evaluation - page 348

Elapsed Time (min) Deformation Dial, H (in.) Proving Ring Dial (in.)

0 0 0

0.005 0.0012

0.010 0.0025

0.015 0.0037

0.020 0.0053

0.025 0.0066

0.050 0.0140

0.075 0.0201

0.100 0.0256

0.125 0.0294

0.150 0.0321

0.175 0.0337

0.200 0.0331

11.25 0.225 0.0305

[It is, of course, necessary to perform triaxial tests on two (preferably,
even three or more) specimens from the same sample at different
chamber pressures in order to evaluate the shear strength parame-
ters. In this example, however, actual data are shown for only one
specimen tested.]
With the preceding data known, necessary computations can be
made as follows:

[A] Specimen Parameters

The height-to-diameter ratio is 5.82/2.50, or 2.33, which is between
2 and 2.5 and therefore acceptable. The initial area A 0 and volume V 0
of the specimen are easily computed as follows:

p D 2
4

2.50

2

p 1 2

A 0 4.91 in . 2

4

V 0 H 0 A 0 5.82 4.91 28.58 in . 3

1 21 2 1 21 2

With the mass and volume of the specimen known, its wet unit weight
g wet can be determined:

ba 1,728
453.6

a 920.20
28.58

122.7 lb ft 3

g wet b >

(The numbers 1,728 and 453.6 are conversion factors: 1,728 in. 3 1 ft 3 ;

453.6 g 1 lb.)

The water content of the specimen may be computed as follows (see
Chapter 4):

939. 92 811.07

w 100 16.9 %

48. 62 811. 07

With water content known, dry unit weight

γ dry can be determined next:

122.7
16.9

g wet

100 100 105.0 lb ft 3

g dry

100 100

>

w