Hydro-Mechanical Properties of an Unsaturated Frictional Material

6.4. VOLUMETRIC BEHAVIOR 131
Vertical strain (-)
Void ratio (-)
0.000
0.005
0.010
0.015
0.020
0.665
0.660
0.655
0.650
0.645
0.640
0.635
0.630
kPa kPa Applied 1.5 3.0 suction: 20.0 1·106 50.0 kPa dry
= 0.66 ratio void Initial specimen Dense
Vertical net stress (kPa) 1000 100 10 1
Figure 6.16: Experimental results of one dimensional compression rebound test for constant
suction condition (dense specimen)
to the results performed under saturated condition, because the corresponding volumetric
water content or saturation is close to zero under this condition (see for instance experimental
result of soil-water characteristic curve for loose an dense specimen in Fig. 6.2 during drainage
process). From the observations it can be concluded that with increasing suction the stiffness
is increasing but after reaching an certain suction value the stiffness is decreasing again.
Comparing the unloading path of all tests one can state, that there is a similar behavior for
all the specimens. The curves are almost parallel.
6.4.2 Collapse Behavior
Results of oedometer tests for estimation of collapse potential are presented in Fig. 6.17 for
Method 1 (left) and Method 2 (right) for loose Hostun sand samples. Volumetric strain versus