Understanding the natural consolidation of slurries using colloid science

Many projects (Marker Wadden, Kleirijperij) have recently been initiated in the Netherlands that involve the reuse of dredged material from silted channels. This dredged material is deposited in large ponds, and left to consolidate. When its dewatering and strength development is found to be adequate, the consolidate slurry is used as building or filling material for dikes, roads and artificial islands. The consolidation of slurries is a complex process that depends on many physico-chemical aspects. Sediment particles in suspension are interacting and this interaction can lead to time-dependent flocculation and settling rates. Settled flocs will create a very open and fluffy bed that will consolidate over time, exhibiting large strains during the primary consolidation regime. At the same time, a substantial amount of fine particles can remain (unflocculated) in suspension due to Brownian motion. The aim of our research is to link the suspension phase to the consolidating phase in a single model. This model combines a traditional 1D large-strain consolidation model with 1D advection-diffusion model as derived in colloid science in the suspension phase. The model is subsequently tested on various samples from the aforementioned projects.