Parametric studies using finite element modeling for the evaluation of the performance of tiered MSE walls under seismic loading

Whenever a need arises to construct a high retaining wall, the construction of a mechanically stabilized earth (MSE) retaining wall in a multi-tiered configuration is a viable approach than the construction of a single-tiered (rectangular wall). However, the behavior of multi-tiered MSE walls is complex, and unfortunately, the behavior of such walls under seismic loading has not yet been entirely investigated. Therefore, this study performs an exhaustive comparative analysis, on multi-tiered and rectangular MSE walls through a finite element method-based numerical computational tool to look into its performance under seismic loading and their potential failure envelope, i.e., wedge angle. Additionally, this study investigates the influence of the parameters such as the number of tiers, offset distance (D), and horizontal seismic acceleration coefficient (k_h) on the walls. The potential failure envelopes of the various wall models are explored, which indicate a combination of overturning and sliding failure accompanied by a distortion of the leveling pad of the walls. However, the sliding behavior reduces as the k_h increases and the overturning failure is more prominent. This study proposes a wedge angle correction factor (C_Θ) to normalize the deviation of the angle of the potential failure plane under seismic loading, based on the assumption that the standard value of the potential failure plane defined by Federal Highway Administration (FHWA) is valid for all multi-tiered walls since none of the design manuals have suggested clear guidelines that can demonstrate the formation and progression of the wedge angle under seismic loading conditions for multi-tiered walls. The factor of safety (FOS) of the various wall models simulated in the present study satisfies the FHWA guidelines, thus suggesting the construction of tiered walls, at places where huge excavation required for the construction of a rectangular wall is impractical. In the numerical simulations, where the FOS obtained is unsatisfactory as per FHWA guidelines, the current study suggests increasing the length of reinforcement and/or decreasing the vertical spacing between the reinforcing layers to enhance the overall stability of such walls.