PVD and DCM columns combined ground improvement for embankment construction

Prefabricated vertical drains (PVDs) and deep cement mixing (DCM) columns combined ground improvement with a vacuum pressure for embankment construction on soft clay deposits has advantages, such as limiting embankment load induced deformation of adjacent areas and reducing total ground improvement cost. However, for design this kind of soft ground improvement, there are no methods for estimating amount of ground deformations as well as maximum tensile stress in the DCM columns. A series finite element analyses (FEA) were carried out to investigate the performance of embankments on combined PVD together with a vacuum pressure and DCM column improved soft deposit. Based on the results of FEA, explicit method for calculating ground settlement under the center of embankments, graphic methods for predicting maximum tensile stress in the column and maximum lateral displacement under the toe of embankments have been established. It is suggested that these methods can be useful tools for design this kind of combined soft ground improvement, and a working example has been demonstrated.