Hydro-Mechanical Properties of an Unsaturated Frictional Material

176CHAPTER 8. NEW SWCC MODEL FOR SAND INCLUDING SCANNING CURVES
Volumetric water content (%)
Volumetric water content (%)
50
40
30
20
10
0
TDR/T 70 mm TDR/T 160 mm 260 mm Flow rate = 30 ml/min
TDR/T 360 mm New model curve fit TDR/T
Transient state column test I
50 0 1 2 3 4 5
40
30
20
10
0
Suction (kPa) specimen Initial void ratio = 0.89 Loose
Flow rate = 100 ml/min
0 1 2 3 4 5
Suction (kPa)
state column test I Loose specimen Initial void ratio = 0.89 1st imbibition Transient
2nd imbibition
Figure 8.4: Experimental imbibition results (1 st imbibition, 2 nd imbibition) and new SWCC
model best fit (loose specimen, transient state sand column test)
depth are given in Fig. 8.4 for loose specimen (see also Fig. E.4 in Appenidx). The tensiometer
and TDR sensor measurements observed for loose specimen during 1 st imbibition in a depth
of 70 mm (TDR/T70 mm) were excluded from the examination, because they show untypical
behavior (measurements are therefore given in grey color in Fig. 8.4). The individual expo-
nential fits to each cross-section of the data reveal the influence of initial imbibition suction
s0. An exemplary comparison of the parameters is given in Tab. 8.2 for the 2 nd imbibition
process of the loose specimen. It is shown that three of the estimated parameters are not
sufficiently different for different depth:
- Parameter β0 that is equal to the saturated volumetric water content and that should be
equal under saturated condition in each depth. The saturated volumetric water content
is approximately θs = 38.5% that is similar to β0.
- Parameter β1 that influences the slope of the curve and is in all depth approximately
β1 = −5.