Hydro-Mechanical Properties of an Unsaturated Frictional Material

116 CHAPTER 6. EXPERIMENTAL RESULTS
- Volumetric water content measurements
The measurements and the resultant soil-water characteristic curves are given in the section
below. In case of steady state tests it was also focused on the volumetric mechanical behavior,
by applying net stress to the specimen. The influence of net stress on the shape of the soil-
water characteristic was observed.
6.2.1 Steady State Test Results
Cumulative water outflow as well as inflow measurement results were derived from the tests
performed in the modified pressure plate apparatus. Experimental results of cumulative water
outflow and inflow during drainage process as well as imbibition process are plotted in Fig. 6.1.
Depending on the suction step it took a period up to 12000 min till reaching equilibrium
condition in the specimen. Before reaching the air-entry value (suction steps between 0
Cumulative water outflow (ml)
Cumulative water inflow (ml)
40
10 20 30
0
-30 -20 -10
-40
0
0 to 0.1 kPa0.1 to 0.5 kPa
0.5 to 1.5 kPa
Time (min) 30000 40000 1.9 to 3.0 kPa
3.0 to 5.0 kPa
5.0 to 20.0 kPa
20.0 to 50.0 kPa
20000 10000 0
Time (min)
1.5 to 0.7 0.7 to 0.5 kPa
0.5 to 0.4 kPa
0.4 to 0.3 kPa
0.3 to 0.2 kPa kPa
0.2 to 0.1 kPa
kPa1.5 to kPa kPa2.8
to 3.0 kPa3.0
to 2.8 5.0 5.0 to 50.0 40000 30000 20000 10000 0
Figure 6.1: Experimental results of cumulative water outflow (top) and inflow (bottom) from
drainage and imbibition process in modified pressure plate apparatus (loose specimen)
1.5 to 1.9 kPa