Experimental analysis of sediment incipient motion in rigid boundary open channels

Incipient motion of sediment is one of the main aspects of the sedimentation process. Determination of the minimum shear stress or velocity required to initiate the motion of sediment particles is a crucial task in the rigid boundary drainage system design. This study investigates incipient motion through laboratory experiments conducted in trapezoidal, rectangular, circular, U-shape and V-bottom cross-section smooth channels using four different size-sands. Experimental data are analyzed using the shear stress and velocity approaches. Shields method is used in the shear stress approach while formulation proposed by Novak and Nalluri is used as the velocity approach. New relationships are proposed for computing shear stress and velocity required for incipient motion in each of the channels. Results are compared with the corresponding models available in the literature. Data collected in this study are found in an acceptable agreement with the existing models. Channel cross-section shape plays an important role in incipient motion of sediment. Among the channels, the rectangular and V-bottom channels require the lowest and the highest shear stress and velocity for the initiation of sediment motion, respectively.