Behavior and Design of Back-to-Back Walls Considering Compaction and Surcharge Loads

Abstract

Back-to-back geosynthetic-reinforced retaining walls are commonly used as approach embankments for bridges and flyovers. Compaction and surcharge loads should be incorporated in the model to understand the realistic behavior of mechanically stabilized earth (MSE) retaining walls through numerical modeling. In this study, a finite-difference method-based numerical model, Fast Lagrangian Analysis of Continua (FLAC 2D, Version 7.0), is used to study the effects of surcharge and compaction stresses on lateral pressures and lateral displacements of back-to-back MSE walls. The ratio of the distance between walls to the height of the wall (W/H) in back-to-back walls is varied from 1.4 through 2.0, and the stiffness of reinforcement from 500 to 50,000 kN/m to cover the entire range of stiffness values of extensible to inextensible reinforcements. The coefficient of lateral pressure, Kr, at the end of the reinforcement zone for W/H = 1.4 is found to be 50% less than that for W/H = 2.0. Plots showing the variation of lateral earth pressure coefficients and lateral deformations versus normalized depth of wall are presented. Maximum tensile forces in the reinforcements along the depth of wall are also analyzed. The lateral pressures at the facing appear to be unaffected with W/H ratio. Finally, a design example showing the external stability analysis of reinforced back-to-back walls is illustrated incorporating the lateral pressures obtained from the study.