Particle size segregation and diffusion in saturated granular flows: Implications for grain sorting in debris flows

Sorting of rocks, boulders, and silt/sand-sized particles according to their size is a characteristic feature debris flow deposits an active process during which significantly affects the mobility. The degree at sorting occurs in flows depends on relative magnitudes granular processes such as particle segregation diffusion. Since are fluid-saturated phenomena, accurate modelling requires understanding influence fluids these processes, have not been systematically studied. Here, we present simulation results associated empirical expressions for diffusion take into account fluid effects due buoyant drag forces. These developed through scaling analysis data obtained from coupled granular-fluid simulations saturated bi-disperse mixtures under simple shear. We further show that using relationships, existing segregation-diffusion continuum equation can be extended model with various types fluids.