Amplification of acceleration is a design concern because it can generate larger accelerations leading
to larger destabilizing dynamic earth pressure and wall inertia. The acceleration amplification factors
at top of the facing wall and at the depth of 5 cm in the reinforced soil zone (Fig. 2, 3a, and 4a) can be
calculated by dividing the outward peak acceleration amplitude by the corresponding base peak
acceleration amplitude. The results of these calculations are plotted versus base acceleration amplitude
in Fig. 9.
The gravity-type RW exhibited a general trend of increasing amplification with increasing base
acceleration, with highest facing wall amplification factor of 1.88 occurring during the final shaking
step of 488 gal at failure. However, for geogrid-RS RW and geocell-RS RW, the amplification factors
increased with increasing base acceleration until the highest facing wall amplification factors of 2.10
and 2.07 occurring during the shaking steps of 711 gal (point A in Fig. 9a) and 643 gal (point C in Fig.
9a) at which initial failure plane has already formed or just started to form. After this, the amplification
factors decreased. In other words, prior to the estimated critical acceleration value (points at A and B
in Figs. 9a) in the cases of geogrid-RS RW and geocell-RS RW the amplification factors increased as
the base acceleration increased but decreased thereafter. This is likely related to formation of failure plane in the unreinforced backfill associated with the change of stiffness in the soil, the damping
capacity of the soil-wall system, and the fundamental frequency of the soil and soil-wall system,
which is not the subject of this paper.