RESUSPENSION OF DEPOSITED COHESIVE SEDIMENT BEDS

Surfieial layers of estuarial fine, cohesive sediment beds are deposited from flow and often are in a state of partial consolidation. A series of laboratory investigations were carried out to elucidate the erosional behavior of deposited cohesive sediment beds in flumes using kaolinite. A significant feature of such beds is that they are stratified with respect to the density and the cohesive shear stength. Under a given bed shear stress, erosion occurs at a continuously decreasing rate up to a depth at which the bed shear stress equals the shear strength. This bed shear stress is therefore also equal to the critical shear stress for erosion at that depth. An expression for the rate of erosion relating this rate to the difference between the bed shear stress and the critical shear stress has been obtained. The critical shear stress increases both with depth and with the bed consolidation time. The rate of erosion decreases with increasing consolidation time.