Triaxial Compression Test - Soil Properties: Testing, Measurement, and Evaluation - page 350

The values above fill in the second row of the form on page 360.
Similar calculations furnish values for succeeding given deformation
dial readings and proving ring dial readings needed to fill in the
remaining rows on the form.
It should be emphasized that one or two additional evaluations are
required for additional triaxial compression tests on other specimens of
the same sample at different chamber pressures. Such evaluations are
not included here.

[C] Stress-Strain Curve

The required stress-strain curve is obtained by plotting axial strain
(third column on page 360) along the abscissa versus unit axial load
(seventh column on page 360) along the ordinate. The curve for this
example is the lower one in Figure 22-6. As indicated in the figure, the
values of

σ 3 (given),

p (determined from the curve), and

σ 1 (

p +

σ 3 ) are

Δ Δ

10.0, 40.0, and 50.0 psi, respectively.

Specimen No. 3
σ 3 = 30 psi
Δ

60

p = 55.5 psi
σ 1 = σ 3 = 85.5 psi

Specimen No. 2
σ 3 = 20 psi
Δ

p +

Δ

50

p = 47.6 psi
σ 1 =

p +

σ 3 = 67.6 psi

Δ

40

30

Specimen No. 1
σ 3 = 10 psi
Δ p = 40.0 psi
σ 1 = Δ p + σ 3 = 50.0 psi

20

10

0 10 20 30 40 50

Axial strain, Δ H (in./in. x 10 -3 )

H 0

1 2
J D

S R 1 0 1 1
6 / 8 / 08

Sample No. Project No.

Plotted by Date

Figure 22-6 Unit Axial Load versus Axial Strain Curves