Hydro-Mechanical Properties of an Unsaturated Frictional Material

6.2. SOIL-WATER CHARACTERISTIC CURVE 119
stresses are presented in Fig. 6.4 for loose specimen. Drainage results as well as imbibition
results are given.
Soil-water characteristic curve results derived from measurements performed during steady
state test in the column testing device I shows Fig. 6.5. After removing or inducting water
equilibrium conditions were achieved. The measured water contents and pore water pressures
at equilibrium condition were measured and linked to the soil-water characteristic curve as
given in Fig. 6.5 for loose and dense specimen. The diagrams show initial drainage curves and
imbibition scanning curves derived from the 3 upper depths in the column. The soil-water
characteristic curve takes place in a narrow range of matric suction. After the first drainage
procedure the occluded air could not be replaced by the following imbibition process.
In general experimental results from steady state tests derived in modified pressure plate
apparatus and sand column testing device I show an influence of void ratio on the shape of the
Volumetric water content (-)
Saturation (-)
Void ratio (-)
50
40
30
20
10
0
process, σ*= 20 kPa Drainage process, σ*= 10 kPa Drainage process, σ*= 0 kPa Imbibition process, σ*= 20 kPa Drainage
0.1 1 10 100
Imbibition process, σ*= 10 kPa Imbibition process, σ*= 0 kPa
1.0
Loose specimen
Suction (kPa)
ratio = 0.89
0.8
void Initial
0.6
0.4
0.2
0.0
0.90
0.1 1 10 100
0.89
Suction (kPa)
0.88
0.87
0.86
0.1 1 10 100
Suction (kPa)
Figure 6.4: Experimental results of soil-water characteristic curve applied with net stress from
steady state test in modified pressure plate apparatus (loose specimen-left, dense specimenright)