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scaling factors in the centrifuge model. The scaling factor on the tensile strength
of reinforcement l
Rs
(S
Rm
/S
Rp
)is1/N
2
. As the model reinforcement width is also
reduced by 1/N, the scaling factor on tensile strength as well as the elongation
rigidity of reinforcement per unit width become 1/N in the centrifuge. While in
the small-scale gravity model, l
Rs
(S
Rm
/S
Rp
)is1/N
3
for one reinforcement and
1/N
2
for per unit width, because the scaling factor on force in the gravity model is
1/N
3
.1/N
2
times smaller strength and elongation rigidity per unit width in the
model reinforcement than those in the prototype causes the problems in the model
as explained in reasons (2) and (3).
The above-mentioned advantages of the centrifuge models are relative
ones to the small-scale gravity models. In addition, the centrifuge models can
be more easily and economically conducted than the large-scale model. This
advantage is very crucial in the study of the mechanical behavior of soil
structures affected by many factors. The reinforced earth slopes and walls
have many conditions, which also include many factors or variables, as
shown in Table 2.
Therefore, a large number of tests are required in order to investigate the
effects of these factors under well-controlled test conditions. Mitchell et al.
(1988) conducted 38 centrifuge tests on reinforced soil walls and discussed the
effects of reinforcement extensibility, type of facing, compressibility of
foundation, and surcharge. Satoh et al. (1998) reported a series of centrifuge
Table 2
Conditions and Factors Considered in the
Performance of Reinforced Earth Wall
Conditions
Factors or variables
Soil
Cohesionless soil
Cohesive soil
Density
Reinforcement
Type (grid, metal strip, etc.)
Strength
Extensibility
Length
Spacing
Construction sequence
Wall or slope
Slope angle
Facing
Foundation
Compressibility
External load
Self-weight or height of wall
Surcharge
Seismic force (k
h
, k
y
, frequency)
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