Three-dimensional numerical analysis of a DCM column-supported highway embankment

This paper presents a three-dimensional numerical analysis of a well-monitored DCM (deep cement mixing) column-supported embankment for a highway in Thailand. A coupled three-dimensional mechanical and hydraulic numerical model was used for this analysis, and the results are compared with the field measurements, including settlement, load distribution between soil and DCM columns, excess pore water pressure and lateral movement. The numerical model reasonably simulated the performance of the DCM column-supported embankment compared to the observed data. From the field measurements, the surrounding soils carried approximately half an embankment load, while the rest was transferred to the stronger soil layers below. The computed maximum bending moment in the column under the toe of the embankment was located at the interlayer between the fill material and soft clay due to the existence of thick fill material layer. A parametric study was conducted to investigate the influence of five key factors on the performance of the DCM column-supported embankment. The parametric study indicated that the factor of safety against bending moment failure (FSbending) seems to be the most important factor of safety to design in this study. The embedded column was more suitable than a fixed column to support high embankment load due to the higher moment capacity of the column with the same improvement area ratio ar, while the reduction ratios of settlement (Rs) and lateral movement (Rl) were not significantly different. If the floating column is chosen, sufficient improvement depth to produce the column tip laterally restrained is necessary to not only reduce the lateral movement but also increase the FSbending. The dr of greater than 0.7 is suggested in this study.