Performance Evaluation of an Embankment on Soft Soil Improved by Deep Mixed Columns and Prefabricated Vertical Drains

TLDR

A combined ground‑improvement method using deep mixed columns and prefabricated vertical drains has been adopted to increase bearing capacity and accelerate consolidation of soft soil embankments. The authors built a well‑instrumented embankment and performed 3D and 2D finite‑element analyses in ABAQUS, using a plane‑strain conversion to simulate 3D conditions. Field and numerical results agree well, showing that deep mixed columns improve embankment stability while prefabricated vertical drains accelerate soft‑soil consolidation.

Abstract

A combined ground-improvement method has recently been adopted for embankments on soft soil that involves the use of both deep mixed (DM) columns and prefabricated vertical drains (PVDs) to increase the bearing capacity and accelerate the consolidation of the soft soil. A well-instrumented embankment was constructed in a field using this ground-improvement method to verify its performance. Three- (3D) and two-dimensional (2D) finite-element analyses were conducted to evaluate the performance of an embankment constructed over soft soil improved by the DM columns and PVDs. In the 2D analysis, a plane-strain conversion method was used to simulate the 3D condition. The finite-element software ABAQUS was used for these analyses. The computed settlements, excess pore-water pressure, load transfer from the surrounding soil to the columns, and lateral displacements in both analyses are compared with the field data, and good agreement was found between the computed and measured data. The field and numerical results show that the DM columns enhanced the stability of the embankment over soft soil, whereas the PVDs accelerated consolidation of the soft soil.