As is known to us, Durand model has been widely used to calculate the friction head loss in the pipeline heterogeneous slurries. Like other popular models, however, it couldn’t give reasonable predictions to the big gravel particles flow either. Figures 6, 7 & 8 show that the Durand model neither simulates the “double-peak” flow of gravel 2 mixture, nor predicts the flow resistances of gravel 3 and gravel 4 mixtures.