Performance and Analyses of Mechanically Stabilized Earth Walls in the Tecomán, Mexico Earthquake

This paper discusses the performance and analysis of four mechanically stabilized earth (MSE) wall bridge approaches shaken by the 2003 Tecomán, Mexico earthquake. Strong shaking during the earthquake caused varying degrees of permanent displacement in several of the MSE walls. Immediately after the earthquake a geotechnical engineering reconnaissance team made detailed damage surveys of each wall. Complete design and construction data were later obtained. The analyses indicate that pullout of the upper reinforcement layers was the mechanism most likely responsible for the seismically induced deformation of the MSE walls. The upper layers of reinforcement were vulnerable to pullout because of the low levels of confining stress and the limited number of reinforcing elements per unit width. While pullout was the principal deformation mechanism, other factors contributing to deformation include large peak ground acceleration, more than twice the design value, and possible directional effects in the ground motion, which directed significant energy to the direction perpendicular to some of the walls. The latter finding concurs with observations made during the reconnaissance, where a clear directional bias was observed in the MSE wall deformations. The applicability and validity of the pseudostatic and sliding block methods of seismic analyses are discussed in light of the observed performance.