The Fractal Structure of Cohesive Sediment Aggregates

The forces between particles and the structure of cohesive sediment aggregates to a large extent determine various mechanical and rheological properties of mud flocs and mud beds. The unifying concept of self-similar fractal geometry is adopted to model the complex and much variable structure of cohesive sediment aggregates. The fractal aggregate model, which has been applied to aggregation in colloidal suspensions over more than a decade, is related to Kroneʹs (1963) notion or orders of aggregation. However, self-similarity on all scales implies that a unique relationship exists between aggregate size and number of primary particles that form the aggregate. The consequences of self-similar fractal structure concerning density and strength of flocs, and permeability, yield strength and viscosity of mud beds are analysed in some detail. Comparison of the results obtained with experimental data from the literature supports the fractal model.