Experimental study on incipient shear stress of consolidated cohesive sediment

This paper analyzes the incipient motion mechanism of consolidated cohesive sediment. An experimental device based on previous studies was designed to investigate the influencing factors of the incipient shear stress, including the consolidation time, the density of dry bulk, cohesive particles content, and the composition of sediment mixtures. The experimental results indicated that the incipient shear stress of cohesive sediment increased with the increase of consolidation time, dry bulk density, and content of cohesive particles. The incipient motion mechanism of cohesive particles was further investigated using experimental data and theoretical analysis. A formula of the incipient shear stress for cohesive sediment was proposed herein, which is related to both the content of cohesive particles and the relative dry bulk density. The proposed formula was validated by the experimental data, and the calculated values of incipient shear stress using the formula were in good agreement with the experimental results.

Condition for the Incipient Motion of Non-Cohesive Particles Due to Laminar Flows of Power-Law Fluids in Closed Conduits

The results of an experimental study on the condition of incipient transport of non-cohesive particles due to the flow of a power-law fluid in a rectangular pipe are presented in this article. The pipe can change its inclination, and experiments were carried out with positive and negative slopes. From a dimensional analysis, the parameters that define the condition of incipient motion were found and validated with experimental data. Thus, the threshold condition is well defined by a particle Reynolds number and a Galileo number, properly modified to take into account the power-law rheology of the fluid. The experimental data are also presented in a standard Shields diagram, including the data obtained in other studies carried out in open-channel laminar flows of Newtonian and power-law fluids.