Hydro-Mechanical Properties of an Unsaturated Frictional Material

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CHAPTER 7. ANALYSIS AND INTERPRETATION OF THE EXPERIMENTAL
RESULTS
m (-)
Stiffness modulus (10³ kPa)
1.0
0.8
0.6
0.4
0.2
0.0
ratio = 0.59 (Schanz 1998) Void ratio = 0.66 Void
0.5 0.6 0.7 0.8 0.9
Void ratio = 0.89 Void ratio = 0.92 (Schanz 1998)
40
1.0 =100 kPa
σref
30
20
10
0
Void ratio (-)
0.5 0.6 0.7 0.8 0.9 1.0
Void ratio (-)
Figure 7.20: Calculated parameter ˆm and stiffness modulus for dry specimens with different
void ratios
The results of the stiffness moduli, that were derived from the experimental results are
given in Tab. 7.3. This table summarizes stress dependent stiffness moduli, that were es-
timated for a low vertical net stress (σ = 12 kPa) as well as a high vertical net stress
(σ = 100 kPa) to see the development of this value. For all calculations a reference stress of
σref = 100 kPa was used. For the stiffness modulus Eoed an increase with increasing suction
(up to 20 kPa) is observed for σ = 12 kPa and σ = 100 kPa. With further increase in suction
the stiffness modulus is decreasing again. For the parameter ˆm, values between ˆm = 0.62 to
0.81 for dense and ˆm = 0.58 to 0.76 for loose specimens were derived during loading path. For
the un-/reloading path constant ˆm = 0.97 for dense specimen and ˆm = 0.93 for loose spec-
imen was calculated. In Fig. 7.20 parameters ˆm calculated from oedometer test results are
given for dry specimens and compared to results derived by Schanz (1998) for Hostun sand.
According to ˆm the author found stiffness moduli of Eoed = 17.000 kPa (loose specimen) and
Eoed = 35.000 kPa (dense specimen) for vertical net stress σref = 100 kPa. As can be seen
in Fig. 7.20 the results of parameter ˆm and the stiffness modulus from the present study fit
well to the results given in literature.