Centrifuge Modeling of Seismic Performance of Reinforced Earth Structures - Reinforced Soil Engineering: Advances in Research and Practice - page 415

the elongation rigidity of the geogrid and the observed strains in the model and
the real geogrids under the same vertical pressures. From these observations
they confirmed the similarity of pullout resistance between the model and the
prototype. Zimmie at al. (1994) evaluated the dynamic geosynthetic interface
friction in the centrifuge using a shaking table and found the obtained interface
frictions agreed well with those reported in the literature. Although some
research shows less particle size effects on the performance of reinforced earth
structures, the available data are still limited, which requires more research on
the effect.
Other Effects Especially for Shaking Tests. Measurement in the detailed
behavior of the model is one of the other difficulties especially for shaking tests
using small-scale models under high centrifugal accelerations. In the small-scale
model, not only particle size but also sensor size may affect the behavior; even it
is difficult to instrument the sensors in it. Therefore, in order to conduct fully
instrumented centrifuge model tests, a relatively large-scale model under small
centrifugal accelerations is normally adopted, which is only available for a large
shaking table on centrifuge. In other words, middle-size tests using 1-g shaking
tables may provide better information about the detailed behavior including
deformation, earth pressures and accelerations in the ground, and tensile strains
of the reinforcements than small-scale centrifuge tests, although there are
limitations in the similitude of 1-g models explained above. For example, Koseki
et al. (1998) give very interesting results about the seismic performance of
reinforced earth walls under strong earthquakes from shaking table and tilting
tests. Using the observed results, they discuss the applicability of current
design methods against strong seismic motions like the 1995 Hyogoken-Nanbu
earthquake.
Applying seismic forces is also one of the difficult and challenging parts
in the simulation of earthquake motions under high centrifugal acceleration
fields. Now many shaking tables are available in many centrifuge research
centers all over the world, especially in Japan (Kimura, 2000), but they are
very limited in multidirectional shakers (Shen et al., 1998; Takemura et al.,
2002). As many analytical researchers have pointed out, the effects of vertical
motion on the seismic stability of reinforced earth, for example, Cai and
Bathurst (1996), Ling et al. (1997), further development of the multi-
directional shaker on centrifuge will expand the applicability of centrifuge
modeling on this problem. But not only a very sophisticated centrifuge shaking
table but also simple tilting tests are very useful to show the applicability of
the pseudo-static approach in the seismic design of reinforced earth by the
combination of shaking table tests, which was actually done with a 1-g test by
Koseki et al. (1998).