Hydro-Mechanical Properties of an Unsaturated Frictional Material

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CHAPTER 7. ANALYSIS AND INTERPRETATION OF THE EXPERIMENTAL
RESULTS
Influence of void ratio
Soil-water characteristic curves derived for dense and loose specimen from transient state tests
are presented in Fig. 7.6. Similar to the steady state tests a decrease in void ratio causes a
shift of the soil-water characteristic curve to larger suction values (i.e. ψaev,dense > ψaev,loose,
θr,dense > θr,loose).
Influence of loading path direction
Similar to the steady state tests the drainage and imbibition curves derived from transient
state test are not unique (see also Fig 7.7). The imbibition curves measured in different depths
at different conditions on the main drainage curve are found to be scanning imbibition curves.
For the loose and the dense specimens the imbibition scanning curves measured in the upper
part of the sand specimen start at a higher suction value than the imbibition scanning curves
measured in the lower part of the sand specimen. These curves are located within the main
drainage-imbibition hysteresis.
Volumetric water content (%)
Volumetric water content (%)
50
40
30
20
10
0
50
40
30
20
10
0
θ's= 39%
specimen - drainage Dense specimen - drainage Loose
0.1 1 10 100
Suction
θ's= 35% ψaev= 1.6 kPa ψaev= 2.1 kPa
(kPa) 5%, ψr= 2.7 kPa
θr= 6%, ψr= 3.0 kPa
θr=
47% θs= 41% ψaev= 1.7 kPa
θs=
ψaev= 1.9 kPa
0.1 1 10 100
Suction
θr= 8%, ψr= 3.8 kPa
(kPa) 6%, ψr= 3.6 kPa Loose specimen Initial void ratio = 0.89 Dense specimen
θr=
Initial void ratio = 0.66
Figure 7.6: Influence of void ratio on the shape of the soil-water characteristic curve (transient
state tests)