Factors affecting earthquake behavior of mechanically stabilized earth walls

Mechanically Stabilized Earth (MSE) Walls are flexible retaining systems and their use in various applications has become very popular in recent years. Reliable design of MSE Walls requires an understanding of their behavior under earthquake loading conditions. Recent developments in software utilizing numerical methods such as the Finite Element Method (FEM) have made it possible to analyze the seismic behavior of these types of complex structures. The main goal of this study is to understand the behavior of MSE Walls under earthquake loading conditions. A parametric study was conducted using the FEM computer program PLAXIS v8.6 utilizing Hardening-Soil model. Frequency-dependent harmonic loading with a peak ground acceleration of 0.2g was applied on models with a constant damping ratio of 10%. For the harmonic loading, seven frequencies were selected around the estimated natural frequency of the MSE Wall. 8 m high MSE Walls were modeled with 12 different reinforcement design configurations and each model was excited with seven (7) different input ground motions. A matrix consisting of 84 analyses was generated in order to investigate the effect of the reinforcement length to wall height ratio (L/H), reinforcement stiffness (EA), vertical spacing of reinforcements (Sv), and frequency of the input ground motion on the overall MSE Wall response. Based on the results of the analysis, bulging behavior was observed at the end of the construction phase and outward movement of the top of the wall after the seismic loading. At the end of both stages, the horizontal displacement of the uppermost (top) reinforcement decreased by an increase in L/H ratio and EA, it also decreased by a decrease in Sv. Axial forces showed a similar trend with displacements, and they were mostly influenced by the change in Sv. The maximum amplification in the MSE Wall occurred for the seismic frequency at the estimated natural frequency of the MSE Wall indicating the significance of natural frequency of the structure in seismic analysis.