Numerical Analysis of Stability of Geosynthetic-Reinforced Embankments over Aggregate Columns-Improved Soft Ground under Undrained Conditions

Abstract

Geosynthetics have been increasingly used as basal reinforcement over aggregate columns to support embankments on soft ground. The current practice often simplifies the column-improved ground into a homogeneous mass characterized by a weighted average strength between columns and soils as an equivalent strength method for stability analyses. This study used two-dimensional (2D) numerical software based on the finite difference method to assess the accuracy of the equivalent strength method as compared with an individual wall method, in which individual columns at spacing were converted into walls with equivalent strength and modulus based on weighted average areas. The numerical models with embankments over individual aggregate walls-improved soft ground were first verified against the numerical results from past studies under undrained conditions, in which no geosynthetic basal reinforcement was used. This study utilized geosynthetics as basal reinforcement to improve the stability of aggregate wall-supported embankments and considered the effects of the groundwater table that were not considered in the previous studies. Overall, the equivalent strength method overestimated the factor of safety (FS) compared to the aggregate wall method, and its overestimation increased with increasing area replacement ratio. Geosynthetic reinforcement increased the FS but had limited effect on the overestimation by the equivalent strength method. An equation for estimating the reduction factor is suggested if the equivalent strength method is used for the analysis of the stability of geosynthetic-reinforced embankments over aggregate columns-improved soft ground under undrained conditions.