965
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
Experimental study on compaction grouting method for liquefiable soil using
centrifuge test and X-ray tomography
Etude expérimentale sur la CPG pour le sol liquéfiable par centrifugation et tomographie à rayons X
Takano D., Morikawa Y.
Geotechnical Engineering Division, Port and Airport Research Institute, Japan
Nishimura S.
Faculty of Engineering, Hokkaido University, Japan
Takehana K.
Engineering Department, Geodesign Co., Ltd., Japan
ABSTRACT: Compaction grouting, an in-situ static compaction technique by means of grout injection, has been increasingly adopted
for improving the liquefaction resistance of loose sandy ground in recent years. The surrounding ground’s stress changes and
densification induced by grout injection are considered to be an important cause for the stabilization effects. The present study
investigates characteristic of ground deformation by simulating compaction grouting processes in micro focus X-ray tomography. 3D
Volumetric Digital Image Correlation (V-DIC) techniques were applied to the tomographic images. V-DIC analysis of in-situ-
acquired tomographic images provides a characterization of porosity, displacement and strain field of model ground. Additionally,
simulation of ground injection and shaking table test was carried out in a geotechnical centrifuge to evaluate stress changes and
liquefaction resistance of improved sandy soil.
RÉSUMÉ : Coulis compactage, une technique in-situ compactage statique à l'aide d'injection de coulis, a été de plus en plus adoptée
pour améliorer la résistance à la liquéfaction du sable loos terrain ces dernières années. Changements de contrainte du sol environnant
et de densification induite par injection de mortier sont considérées comme une cause importante pour les effets de stabilisation. La
présente étude examine caractéristique de la déformation du sol en simulant les processus de compactage coulis au point tomographie
à rayons X micro. 3D volumétrique Digital Image Correlation (V-DIC) techniques ont été appliquées aux images tomographiques. V-
DIC analyse in-situ acquis par images tomographiques fournit une caractérisation de la porosité, de déplacement et champ de
déformation du sol modèle. En outre, la simulation de l'injection de sol et de test table à secousses a été réalisée dans une
centrifugeuse géotechnique pour évaluer les changements de résistance au stress et la liquéfaction de sol sablonneux améliorée.
KEYWORDS: compaction grouting, ground improvement, liquefaction, sand, full field measurement.
1
INTRODUCTION
In-situ static compaction by means of grout injection (CPG) is
widely used as a countermeasure against liquefaction in loose
sandy ground (e.g. Boulanger and Hayden 1995, Miller and
Roycroft 2004). An increase in the liquefaction resistance of
sand caused by compaction grouting is presumed to derive from
three possible mechanisms. They are, (i) increase in the lateral
confining stress, (ii) densification and (iii) reinforcement by
hydrated and hardened grout piles. Especially, the surrounding
ground’s stress changes and densification induced by grout
injection are considered to be an important cause for the
stabilization effects. However, systematic studies of ground
condition changes due to compaction grouting have been
limited in number.
The author’s research group has been studied about ground
behavior due to grout injection especially focusing on stress
change due to grout injection. The present study evaluate
characteristic of ground deformation by simulating compaction
grouting processes in 1g and centrifuge model test. In 1g test,
the deformation process of the model ground by grout injection
was visualized using X-ray computed tomography (XRCT).
Moreover, 3D Volumetric Digital Image Correlation (3D V-
DIC) techniques were applied to the x-ray tomographic images
in order to discuss deformation of the ground quantitatively. 3D
V-DIC analysis of in-situ acquired tomographic images
provides a characterization of porosity, displacement and strain
field of model ground. Additionally, simulation of ground
injection and shaking table test was carried out in a geotechnical
centrifuge to evaluate stress changes and liquefaction resistance
of improved sandy soil.
2
SUMMARY OF TESTING
A microfocus X-ray tomographic scanner and a beam-type
geotechnical centrifuge owned by Port and Airport Research
Institute Japan were used in this study. Figure 1 illustrates a
typical arrangement of grout piles with regular spacing in a
triangular pattern. In order to simulate completion of this
improvement arrangement in a physical modeling in laboratory,
a cylindrical soil container with diameter of 60 mm (see Fig. 2)
and hexagonal cylinder with diameter of 100 and 160 mm (see
Fig. 3) are used for the XRCT test and the centrifuge test,
respectively. The difference of diameter of soil container in
centrifuge test presents the different pile spacing or
improvement ratio and rigid wall of soil container simulates
improved area by pre-injected grout piles. The ground was
Figure 1. Illustration of compaction grouting
(bottom-up pattern)
４
Improved zone
by one grout pile
Lifting rod
Pile diameter,
d
Pile spacing,
x
１
２
３
５
６
７
Injection
