Structures constructed above soft clay could face problems due to its characteristics, where soft clay has high compressibility, low permeability, and low shear strength. One of the soil treatments for soft clay is using prefabricated vertical drain (PVD) with vacuum, where this combined method shortens drainage path and increases consolidation rate. A finite element method (FEM) study was conducted to see the long-term effect of this method. Analysis was carried out on soil settlement, lateral displacement and pore pressure changes during construction and long after. The final result shows that a rebound happened after the vacuum stopped, and was continued by secondary settlement. Soil moved laterally inward to the vacuumed area during treatment, and moving outward slowly after the treatment is done. The longer duration of vacuum affecting settlement and lateral displacement increase.

Keywords : Soft Clay; Prefabricated Vertical Drain, Vacuum Consolidation Method, Long Term Effect.