Cohesive Sediment Characterization by Combined Sedimentation and Rheological Measurements

A laboratory characterization of cohesive sediment has been carried out in which data obtained from standard sedimentation and rheological measurements were combined in a determination of the critical solid concentration for the detection of elasticity in a weakly cohesive suspension. The corresponding storage modulus and shear stress are very critical in any in situ rheometry of sediments, especially in the study of mud-water surface erosion in a flume. Sedimentation results showed that particle size distribution rather than surface treatment controlled the rheological behavior of the suspension while the critical solid concentration for the appearance of three-dimensional space-filling network, showing some measurable elasticity in the suspension, occurred in the region of 0.015. This parallel between the consolidation behavior and shear rheology development for the flocculating system has been established. This technique could be an adjunct to the laboratory characterization of cohesive sediments for the estimation of critical shear stress for surface erosion, especially in a typical flume experiment under water wave pressure.