Model Tests of Seismic Stability of Several Types of Soil Retaining Walls - Reinforced Soil Engineering: Advances in Research and Practice - page 325

initial values measured before starting shaking. The d top -values were evaluated at
the same moment as the reaction forces were evaluated. In the early shaking
steps, the normal stress measured at the toe of wall base (with loadcell LT7 in
Fig. 13a) increased rapidly. It suddenly decreased, however, after showing a peak
state (at the d top -value of around 20mm), suggesting a local failure due to loss of
bearing capacity. After this peak state, the d top -value accumulated rapidly. The
normal stress measured at a location next to the toe of wall base (LT6) showed a
similar trend, while its peak value was much smaller than that of LT7. On the
other hand, the normal stresses measured near the heel of wall base (LT4 and
LT5) decreased in the early shaking steps, followed by a slight increase with the
occurrence of the local failure near the toe of wall base.
As shown in Fig. 13b, the shear stresses measured near the toe of wall base
(LT6 and LT7) increased in the early shaking steps. They decreased after the d top -
value exceeded about 20mm. Such a change of the shear stresses is linked with that
of the corresponding normal stresses. As shown in Fig. 13c, therefore, the
mobilized friction angle computed from the normal and shear stresses measured at
LT6 and LT7 became nearly constant after the d top -value exceeded about 20mm.
Similar behavior was observed with the loadcell LT5. On the other hand, the
mobilized friction angle d b at the heel of wall base (LT4) increased very rapidly in
the early shaking steps. This is because the normal stress decreased to be nearly
zero, as shown in Fig. 13a, so the measured values of d b became rather unreliable.
The effects of the local failure due to a loss of bearing capacity at the wall
toe can be clearly seen in Fig. 14, where the resultant normal reaction force from
subsoil is plotted versus the relative location of its application D/W,where D
Figure 14 Relationships between resultant normal reaction force from subsoil and
relative location of its application.