Hindered Settling of Silt

Abstract

Sediment particles smaller than 64 μm, with a noncohesive base mineral, are referred to as silt. The settling velocity of suspended sediment decreases with increasing concentration due to hindered settling effects. Compared with clay and sand, hindered settling of silt is poorly documented and understood. A formulation is proposed for the hindered settling of silt-water mixtures, derived from physical reasoning. The effect of silt on the mixture’s viscosity is addressed in particular. The formulation compares favorably with laboratory experiments on the settling of silt-sized sediment. This study shows that effective settling velocities can be derived from a single concentration time series measured within the settling mixture, provided that the sediment is initially homogeneously distributed.