Influence of Settling Behavior of Soil Particles on the Consolidation Properties of Dredged Clay Sediment

Abstract

Placement of dredged spoils in a slurry form and allowing self-weight consolidation is common in land reclamation works carried out adjacent to water bodies. The influence of the settling behavior of soil particles in clay-water slurry on the homogeneity and consolidation properties of the final sediment were assessed in the current study. Standard one-dimensional and radial consolidation tests were conducted on Port of Brisbane dredged mud, which was remolded at various water contents and salt concentrations and reconstituted. Particle-size distribution curves show the various degrees of segregation that occurred during settlement of soil particles in flocculated and dispersed slurry, prepared and placed in saltwater and freshwater environments, respectively. The vertical and horizontal consolidation coefficients (cv, ch) and the vertical permeability (kv) were found to be fairly uniform throughout the flocculated sediment, whereas for the dispersed sediment significant variation could be observed at various depth levels. The consolidation properties in the horizontal direction (ch, kh) were considerably larger than in the vertical direction (cv, kv) for both the flocculated and dispersed sediment. The degree of anisotropy in the consolidation coefficient, measured by ch/cv, was generally larger for the flocculated sediment than for the dispersed sediment. Proper understanding of the consolidation process and the variability of the consolidation and permeability coefficients with depth is important for the reliable prediction of settlement and the degree of consolidation achieved in the reclamation fill.