Internal Failure of Deep Mixing Columns Reinforced by a Shallow Stabilized Soil Beneath an Embankment

Abstract

The isolated deep mixing columns, particularly the columns near the slope of the embankment, were reported to experience a minor horizontal resistance while supporting an embankment. In order to reinforce these columns and increase the stability of the improved area, which includes the group of columns, a shallow layer produced by shallow mixing method was proposed as a countermeasure. While many studies reported that the isolated columns may fail either by the external failure or the internal failure, the failure of this combined structure including the deep mixing columns and the shallow layer has not well studied yet. In the previous study, overturning and sliding failures were observed as the leading patterns in terms of the external stability, when the combined structure to supports embankment slope. In addition to the study of the external stability, the internal failure pattern of the columns reinforced by the shallow layer was concentrated in this study. It is worth to note that the low-strength columns are used here. Four centrifuge model tests were performed by varying the column strengths in models with and without the shallow layer of reinforcement. The results showed a significant influence of the shallow layer on the failure pattern of the deep mixing columns. The study further discusses the effect of the shallow layer and the column strength on the stability of the supported embankment.