3D Numerical Limiting Case Analyses of Lateral Spreading in a Column-Supported Embankment

This paper presents three-dimensional (3D) numerical analyses of a column-supported embankment case history using the finite-difference method. An undrained end-of-construction analysis is followed by a long-term dissipated analysis, in which all excess pore pressures generated in the undrained loading phase were manually dissipated for the calculation of long-term deformations. The two analyses examined limiting cases for lateral spreading, providing results that envelop case history recordings at the end of construction and 125 days after construction, respectively. Numerical calculations were performed for a unit cell and a half-embankment model. Calibration of large-deformation soil arching behavior in the embankment was achieved by reducing the Young’s modulus and friction angle of loosened zones whose dimensions were modeled after bench-scale and field-scale tests. Numerical results are in good agreement with case history recordings for vertical load transfer, settlements, and lateral displacements. In addition, numerical results are provided for foundation incremental lateral earth pressure profiles, geogrid strains, column bending moment profiles, and column stresses due to combined effects of bending and axial loading so that they can be related to the fundamental aspects of lateral spreading resistance. The increment of lateral earth pressures in the foundation soil was largest at the undrained end-of-construction condition, geogrid strains were largest in the long-term dissipated condition, and column bending moments and column tensile stresses were very large in both scenarios. Furthermore, the geogrid contributions to increasing vertical load transfer to the columns and reducing lateral spreading of the embankment were insignificant, likely due to the subgrade support provided by the top coarse-grained fill layer in the foundation.