The Effectiveness of Applying Vacuum Preloading on the Physical Properties of Soft Soil

Vacuum preloading is observed to have been widely applied as a soil improvement technique in marine clay piles for coastal reclamation purposes. This is required because most of the problematic soil types in Indonesia are soft clay and peat. Meanwhile, soft soils, especially peat, are different from marine clay piles and this necessitates further research on the effectiveness of vacuum preloading methods for peat compared to soft clay. This research was conducted to present a laboratory-scale model of vacuum preloading application to both clay and peat with a focus on their physical properties. The results showed a significant change in water content for peat while the soft clay experienced only a slight change. Furthermore, the migration of fine particles toward the Prefabricated Vertical Drain (PVD) led to localized densification and this restricted the effectiveness of water drainage. The Scanning Electron Microscopy (SEM) images also showed that both clay and peat near the PVD appeared denser compared to farther samples. In the case of peat, SEM images showed clearly visible pores and high permeability even after the vacuum process, suggesting a tendency for water to fill the pores once the vacuum pressure was released. Moreover, the application of vacuum preloading led to anisotropic conditions in both clay and peat with an increase in the horizontal-to-vertical permeability ratio (kh/kv).