Hydro-Mechanical Properties of an Unsaturated Frictional Material

118 CHAPTER 6. EXPERIMENTAL RESULTS
Scanning drainage cycles and imbibition cycles were also performed during the experi-
mental procedure in the modified pressure plate apparatus on 3 loose and 3 dense Hostun
sand specimen. The derived soil-water characteristic curves including scanning imbibition and
drainage curves are presented in Fig. 6.3 for loose and for dense specimen. The volumetric
water content versus suction and saturation versus suction plots are shown, where also the
volumetric water content was back calculated using the final water content measurements and
the amount of water outflow (drainage curve) and inflow (imbibition curve). Comparison of
the scanning cycles of both specimen, the loose and the dense one, clearly show that the dense
specimen is retaining larger quantity of water for a certain applied soil suction value. Due to
smaller voids in the dense specimen, that retain water up to higher suction value, scanning
cycles are located in the top part of the hysteresis loop.
During steady state tests performed in the modified pressure plate apparatus it was also
focused on the volumetric mechanical behavior by applying net stress to the specimen and
thus the influence of net stress on the shape of the soil-water characteristic curve. Volumetric
water content, saturation and void ratio versus suction relationships for different applied net
Volumetric water content (%)
Saturation (-)
50
40
30
20
10
Volumetric water content (%)
Scanning imbibition process
0
0
1.0
0.1 1 10 100 1.0
0.1 1 10 100
Suction (kPa)
Suction (kPa)
0.8
0.6
0.4
0.2
0.0
process Imbibition process Scanning drainage process Drainage
Saturation (-)
Loose specimen
0.1 1 10 100
Suction (kPa)
50
40
30
20
10
0.8
0.6
0.4
0.2
0.0
0.1 1 10 100 specimen Initial void ratio = 0.66 Dense
Suction (kPa)
Initial void ratio = 0.89
Figure 6.3: Experimental results of soil-water characteristic curves including scanning
drainage and imbibition curves from steady state tests performed in the modified pressure
plate apparatus (loose specimen-left, dense specimen-right)