Dimensionless Erosion Laws for Cohesive Sediment

Abstract

AbstractA method of achieving a dimensionless collapse of erosion-rate data for cohesive sediments is proposed and shown to work well for data collected in flume-erosion tests on mixtures of sand and mud (silt plus clay sized particles) for a wide range of mud fraction. The data collapse corresponds to a dimensional erosion law of the form E∼(τ−τc)m, where E is erosion rate, τ is shear stress, τc is the threshold shear stress for erosion to occur, and m≈7/4. This result contrasts with the commonly assumed linear erosion law E=kd(τ−τc), where kd is a measure of how easily sediment is eroded. The data collapse prompts a re-examination of the way that results of the hole-erosion test (HET) and jet-erosion test (JET) are customarily analyzed, and also calls into question the meaningfulness not only of proposed empirical relationships between kd and τc, but also of the erodibility parameter kd itself. Fuller comparison of flume-erosion data with hole-erosion and jet-erosion data will require revised analyses o...