The objective of this research program was to evaluate the seismic response of reinforced soil slopes and walls, and to evaluate whether the seismic response of these structures is consistent with the assumptions of current seismic design methods.; A review of seismic field performance carried out as a part of this study shows that reinforced soil slopes and walls have performed well under earthquake loading. However, field reports point out a lack of monitoring in practice, making it difficult to validate seismic design assumptions. In general, the structures tend to be flexible and deform without reaching catastrophic failure. A review of previous experimental studies also shows the inherent flexibility of reinforced soil under dynamic loading. In fact, in most of the studies, the walls were able to maintain their integrity even under severe seismic shaking. Thus, both field and experimental data show that deformations need to be considered in the seismic design of these structures.; Dynamic centrifuge studies were performed on geosynthetically-reinforced slopes and vertical walls reinforced with metallic mesh. The models were constructed with different backfill densities and reinforcements of varying stiffness and length. The results of the centrifuge studies show that the model slopes and walls deform even under relatively small shaking. Amplification occurs at small to medium peak base accelerations, depending on the backfill density, and deamplification occurs at greater amplitudes. Densification of the backfill was observed due to seismic shaking.; The data show that the yield acceleration is a function of the backfill density. The data also show that observed horizontal deformations were reduced by using denser backfills and stiffer reinforcements, by shaking the models with smaller intensity and shorter duration events, and by decreasing the inclination of the slope face. The length of the reinforcements did not strongly affect earthquake-induced deformations for values between 70%H and 90%H, which is typical of field conditions.; "Failure," as defined by the development of large deformations, occurred through significant horizontal and vertical deformations evenly distributed throughout the crest. None of the reinforcements ruptured in any of the tests and the reinforcements tended to spread out deformations throughout the reinforced zone and did not allow them to localize them along a discrete failure surface. A significant amount of vertical deformations was also observed, especially near the facing. Finally, the model slopes and walls were generally under-designed by standard, static design methods, and yet no catastrophic failures were observed even after undergoing a series of intense shaking events.; The results of these studies do not support the assumptions of traditional limit equilibrium-based seismic design methods. In fact, discrete failure surfaces did not form in any of the models and the models did not deform rigidly in block-like, outward motions. The slopes and walls deformed in a ductile manner under seismic loading, suggesting that a deformation-based seismic design method may be more applicable. The data in the current study, modified to include broader field conditions, can be used to estimate seismically-induced deformations for reinforced soil slopes and walls and suggest that an empirically-based approach to the evaluation of seismically-induced deformations of reinforced soil slopes and walls is feasible.
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