Vacuum consolidation of soil: clogging effect, varying permeability and compressibility

Abstract

The clogging of a soil pile in vacuum preloading of dredged soil combined with a prefabricated vertical drain (PVD) was investigated through laboratory model tests and analytical modelling. Variation in the water content and permeability of soil around the PVD clarified the formation of a soil pile. Seepage and consolidation tests on the formed soil pile indicated that the clogging effect slowed down the drainage of pore water rather than stopping it. Taking the soil pile as a filter layer, an analytical model was established incorporating the clogging effect and the varying permeability and compressibility of soil. Finally, based on a comparison of existing results and the analytical model, an empirical linear relationship was developed for estimating the likely range of the permeability and scale of a soil pile in terms of the reduction in the void ratio for vacuum-assisted soil consolidation. The proposed model simulated the consolidation process of soil with a high water content appropriately. A soil pile with lower permeability or larger diameter led to more serious clogging effects on the soil consolidation. The development of the clogging effect decreased with an extension of the soil pile.