Effect of varying void on consolidation of dredger fill under vacuum preloading

Dredger fill changes from fluid to soil and its void reduces markedly during the consolidation of reclaimed ground under vacuum loading. Because both permeability and compressibility are functions of void ratio, the consolidation coefficient of dredger fill changes greatly. The prediction by current design method is much different from engineering practice because the consolidation coefficient in this method is taken as a constant. In order to account for the effect of varying void on consolidation, the relation between consolidation coefficient and effective stress is derived; and a consolidation model for dredger fill is built by applying this relation to Barron's consolidation theory. The model is proved by comparing the result of this model with that of model test. The analysis result shows that the consolidation coefficient of dredger fill decreases with the void during the consolidation. Therefore, the consolidation of reclaimed ground is rapid in the initial stage and slow later. The quick decrease of the permeability of soil near the drainage board area will hinder the consolidation of soils in the farther area. Therefore, compared with the result of current design model, the consolidation of reclaimed ground is slower in the later stage and the whole period of consolidation is longer.