DCM Columns and PVDs Hybrid Ground Improvement for Embankment Construction

A case history of embankment construction on soft clay deposit improved by a combination of deep cement mixing (DCM) columns and prefabricated vertical drain (PVDs) installation method was simulated and investigated by finite element analysis (FEA). The function of the DCM columns is to control the settlement and lateral displacement under the toe of the embankment, and the function of the PVDs is to accelerate consolidation rate for a zone under the central of the embankment. For this case, only the surface settlements were measured, and the simulations agree with the measured data well, while the results of FEA give relative large lateral displacements under the toe of the embankment with a value of about 370 mm. Further numerical investigation was carried out assuming part of the preloading load was vacuum pressure, with which to result in the similar final surface settlement. The numerical results indicate that with the vacuum pressure, the lateral displacement under the toe of the embankment as well as the maximum compressive stress in the columns can be reduced significantly. These results indicate that combination of DCM columns and PVDs installation with vacuum pressure as part of preloading pressure can be an effective and economic ground improvement method for embankment construction on soft clay deposit.