Incipient Motion of Sand Particles on Side Slopes

Several criteria have been theoretically proposed for the critical shear stress of noncohesive sediment on side slopes. However, no laboratory work has ever been done on this problem. A theoretical study of the incipient motion of sediment particles on side slopes is presented, including the effects of viscous sublayer, turbulence and lift force. As a special case of level beds, the theory describes the experimental values reported by several workers. A specially designed rotary wind tunnel permits the evaluation of the critical shear stress on side slopes, and the experiment supports the theory. These works reveal that the lift force can be neglected in estimating the critical shear stress using the proposed theory if the averaged experimental values are concerned, but inclusion of the lift force in the theory is recommended for safety and for describing the lower limit of the possibility of incipient motion.