Practical design procedures of different types of retaining walls against high seismic loads

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In order to establish practical design procedures to evaluate seismic stability of different types of retaining walls against high seismic loads, a series of irregular shaking tests was conducted on retaining wall models consisting of six different types.In some tests, after the first failure plane was formed in the backfill, the second failure place was formed at higher seismic loads. This can be explained by considering the effects of strain localization in the backfill soil and associated post-peak reduction in the shear resistance from peak to residual values along a previously formed failure plane. Such behavior has not been observed in the tilting tests and the sinusoidal shaking tests that were conducted on the same models in the previous study.In these tests, reinforced-soil retaining wall models with a rigid full-height facing exhibited a ductile behavior compared to conventional type retaining wall models such as gravity-type, leaning-type and cantilever-type ones. When the model walls started to tilt, concentration of subgrade reactions at the toe of conventional type retaining walls resulted in local failure due to loss of bearing capacity. On the other hand, under similar conditions, tensile force in the reinforcements of the reinforced-soil retaining walls could be mobilized effectively to resist against the tilting displacement.In addition, performance of retaining walls during the 1999 Chi-Chi earthquake was investigated. It was estimated that damage to conventional type retaining walls was caused by permanent ground displacement along surface faults, large-scale slope movement, loss of bearing capacity in the subsoils, excessive inertia force of the wall, and/or insufficient compaction of the backfill. It was also shown that extent of damage to reinforced-soil retaining walls using keystones as a facing was affected by the amount of vertical spacing of the reinforcements under otherwise similar conditions.