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Figure 3
Plan of model reinforcement layer.
layers. In order to evaluate the shear resistance angle of the batch of sand used in
the model tests, a series of plane strain compression (PSC) tests was performed.
The specimens were prepared by air pluviation to obtain the same density as in the
model tests. The PSC tests were performed at constant low confining pressure of
9.8 kPa so as to simulate the low stress level in the model tests. It should be noted
that the direction of the major principal stress s 1 is normal to the bedding plane
direction in these PSC tests.
Figure 4 shows the relationships between the principal stress ratio s 1 /s 3 and
the axial strain e 1 . The peak angle of internal friction f peak was equal to, on average,
51
, mobilized at an axial strain of about 2%. The residual angle of friction f res was
calculated to be 43 8 based on the lowest principal stress ratios in the postpeak regime.
8
5 TEST PROCEDURES
5.1 Model Construction
Models were constructed in a sand box (1400 mm high, 2600mm long, and
600 mmwide in the inner dimensions) using a sand hopper with an inner volume of
about 0.0315m 3 having a 600-mm-long slit. To prepare as homogeneous as
possible sand layers at a target void ratio of 0.650, the falling height of sand, the
traveling speed of the sand hopper, and the opening width of the slit were basically
kept constant at 800 mm, 2.5m/min, and 1mm, respectively. However, to adjust
the surface height of each layer, when needed, the traveling speed and the opening
width of the slit were changed in ranges of 1-3 m/min and 1-3mm, respectively.
Based on preliminary tests, it was confirmed that these changes result in a variation
of void ratio ranging between 0.625 and 0.675.
 
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