Application of displacement-based seismic design approach for MSE walls with uneven reinforcement

Mechanically Stabilized Earth (MSE) walls have been used increasingly as retaining systems since the late 1960s. Inclusion of reinforcement within soil has made it possible to construct steep slopes and embankments. The paper describes the application of a numerical model to evaluate permanent lateral seismic displacement of MSE walls with variable lengths of reinforcement. The numerical model was developed by extending an existing model that was proposed for MSE walls with uniform reinforcement. The approach accounted for the vertical variation in acceleration within the backfill. The predictive capability of the numerical model was verified using centrifuge tests carried out in the large centrifuge at the National Geotechnical Centrifuge at the University of California, Davis. One of the important observations from this study was the beneficial role of longer reinforcements near the surface in reducing permanent wall movement. The proposed numerical model captures many aspects of the characteristic deformation behavior of MSE walls observed in the centrifuge tests. Subsequently, the analytical model was used to assemble a database of lateral permanent wall displacement of MSE walls of height varying between 5 and 10m subjected to base excitations from M6.5 and M8 earthquake events. Important design information such as the required length of reinforcement needed to keep the wall displacement within a certain specified limit can be interpreted from the database.