Shear Strength of Unsaturated Soils - Unsaturated Soil Mechanics in Engineering Practice - page 569

(a)

(a)

(b)

(b)

(c)

Figure 11.64 Stress versus strain curves and presentations of fail-
ure envelope for decomposed rhyolite specimen No. 11C: (a) devi-
ator stress versus strain curve; (b) failure envelope projected onto
τ versus σ -u a plane; (c) line defining slope of shear strength with
respect to matric suction (from Ho and Fredlund, 1982a).

(c)

Figure 11.63 Stress versus strain curves and presentations of fail-
ure envelope for decomposed granite specimen No. 10: (a) deviator
stress versus strain curve; (b) failure envelope projected onto τ
versus σ - u a plane; (c) line defining slope of shear strength with
respect to matric suction φ b

(from Ho and Fredlund, 1982a).

saturated specimens showed an angle of internal friction φ
of 35 ◦ and an effective cohesion c equal to 0.0.
The multistage triaxial tests on the unsaturated compacted
specimens were conducted using the consolidated drained
test procedure. The tests were conducted with a constant net
confining pressure while varying the applied matric suction
(Fig. 11.65). The test results showed the φ b angle to be
16 ◦ when a constant effective angle of internal friction was
assumed during the interpretation of the data.

Two multistage triaxial tests on compacted specimens
were reported by Krahn et al., (1989). The soil was
sampled from a railway embankment at Notch Hill, British
Columbia, and consisted of 10% clay, 85% silt, and 5%
fine sand. The optimum water content was 21.5%, and
the maximum dry density was 1590 kg/m 3 when the soil
was compacted in accordance with the standard AASHTO
procedure. Specimens with a diameter of 38mm and a
height of 75mm were trimmed for triaxial testing from the
compacted soil. Consolidated undrained triaxial tests were
performed on four compacted saturated specimens with
pore-water pressure measurements. The test results on the

11.8.2 Constant-Water-Content Triaxial Tests
Constant-water-content triaxial tests were performed on a
compacted shale and a compacted boulder clay by Bishop