ABSTRACT
Experiment was conducted to study incipient motion of gravel particles in the cohesive mixture of clay-silt-gravel. The clay content was varied from 10% to 50% in the mixture while sand and gravel were taken in equal proportion by weight. The incipient motion condition was visually observed corresponding to the beginning of movement of gravel particles in the mixture. The critical shear stress for gravel particles in the mixture was significantly higher for higher percentage of clay content. The clay percentage was found as dominant factor that govern the incipient motion of gravel particles. Other affecting factors are bulk density and unconfined compressive strength of the mixture. The erosion pattern on the top surface of bed was also observed after the end of each experimental run and found dominancy of gravel particles on the bed surface for low percentage of clay.
