Performance of an embankment supported on soft soil reinforced by stone columns

This paper presents a case study of a bridge approach embankment constructed on a soft soil reinforced by stone columns. The soft soil consisted of highly plastic clay with an undrained shear strength as low as 4 kPa. The thickness of the soft soil ranged from 2.5 to 8.5 m. The stone columns were installed through the soft soil by vibro-replacement technique. The stone columns were extended about 0.5 m into the underlying dense to very dense sand, sandstone or mudstone. The overall performance of the treated soil under the embankment load was evaluated using settlement plates. The field measurements were compared to the predictions of the analytical and finite-element methods. Most of the methods predicted settlements that are comparable to the measured values. Furthermore, the finite-element analysis shows that for deep deposits of soft soil, floating stone columns with a length/depth ratio of 0.5 can be as effective as the end bearing stone columns. Furthermore, the settlement reduction factor decreases with the increase in the area replacement ratio. Beyond an area replacement ratio of 0.4, the decrease in the settlement reduction factor is insignificant.