Hydro-Mechanical Properties of an Unsaturated Frictional Material

7.5. VOLUMETRIC BEHAVIOR 161
Table 7.3: Results for stiffness modulus in MPa for dense and loose specimen
Condition of S=1.0 ψ = 1.5 ψ = 3.0 ψ = 20.0 ψ = 50.0 dry
specimen (-) kPa kPa kPa kPa (-)
loose
Eoed, σ = 100 23.4 25.8 24.7 25.7 23.9 15.1
Eoed, σ = 12 4.9 7.0 6.5 7.1 5.2 6.8
Eur, σ = 100 124.4 158.1 149.0 130.2 145.5 102.9
Eur, σ = 12 13.6 15.1 14.2 15.9 16.7 7.6
dense
Eoed, σ = 100 24.4 30.5 29.3 36.1 28.1 21.5
Eoed, σ = 12 6.0 6.5 7.9 7.6 5.4 10.4
Eur, σ = 100 150.0 131.3 255.5 141.4 168.2 174.0
Eur, σ = 12 9.5 13.6 9.7 14.8 15.1 8.3
To investigate in detail the influence of suction on the stiffness behavior of sand the
compression index Cc and the swelling index Cs were estimated. The results are given in
Fig 7.19. The compression index decreases first for suction less then about 20 kPa, that is
equal to an increase in stiffness, and increases again for higher suction values, that is equal to
a decrease in stiffness. As expected compression index of the dense specimen is less then the
compression index of the loose one, which indicates a higher stiffness. No significant influence
of the suction on the swelling index can be observed.
Cc, Cs (-)
0.00
0.01
0.02
0.03
Matric suction (kPa)
0 1 10 100 10 6
ψ aev,loose
ψ r,loose
ψ aev,dense ψ r,dense
Loose
Loose
Dense
Cc
Dense
Cs Cs Cc
Figure 7.19: Compression and swelling index versus suction