Geoscience Reference
In-Depth Information
Triaxial compression / extension tests.
Dr
=
40%, Isotropic consolidation under 100 kN/m
2
1000
800
600
400
200
0
Grouted Toyoure sand (4.5%)
Toyoura sand
−
200
SilicaTriax.fig
−
400
−
15
−
10
−
5
0
5
10
Axial strain (%)
Fig. 15.30. Comparison ofsand improved bycolloidal silicaand untreated sand
by means of undrained triaxial tests
Toyoura sand Dr
=
50%
DA
=
1%
DA
=
2%
DA
=
5%
95% pore pressure rise
4.5% CollSilicaLiq.fig
0.4
0.3
0.2
Toki et al., 1986
0.1
Liquefaction tests on Toyoura sand (Dr
=
40%)
with colloidal silica (4.5%); consol. 100 kPa
0.0
0.1
1
10
100
1000
Number of cycles to liquefaction
Fig. 15.31. Resistance of sandagainst liquefaction increased by colloidal silica
InFigure15.33,sandof40%relativedensitywasimprovedandwascomparedwithden-
sified sand without grouting. This comparison was made in terms of the residual defor-
mation after 30 cycles of triaxial compression as well as the monotonic behavior after
this cyclic loading. It may be found that the behavior of grouted sand is equivalent with
densification to 80% relative density.
Figure15.34 shows the appearance of solidified colloidal silica. It is substantially soft
and, hence, it is difficult to understand why such a soft material improves the undrained
shear behavior of sand. One possible answer to this question may be the volume com-
pressibility of this material (di Benedetto, 2001). Being soft, this material decreases its
volume upon compression and allows less excess pore water pressure to develop than
