Enhancing the Erodibility of Cohesive Sediments by Applying Mechanical Vibrations

Abstract

The efficiency of dredging, whether with a cutter suction dredger or hydraulic flushing, is closely related to the erodibility of the sediments. It is found that the erodibility of cohesive sediments, which is affected by their rheological properties, could be enhanced by improving their fluidization quality. In this study, a cohesive sediment fluidization and erosion enhancing (CSFEE) device was used to fluidize the sediments during flushing, and the corresponding scour rates of test sediments were investigated. The results indicated that this device, with the combined effects of vibration and air, can significantly enhance the erodibility of cohesive sediments in both the directly and indirectly vibrated areas and that this enhancement is more significant for the sediments with higher initial yield stress. The fluidization of the sediments by mechanical vibration is the key driver for such enhancement. Due to the thixotropy of cohesive sediments, the effects of vibration were time-dependent, whereby the scour rate of test sediments increased with increasing exposure time of the device.