Enhanced horizontal deposition of large stone in granular flow with mixing small spherical grains after slide along slope and free fall

Geophysical mass flows, which could endanger our health, lives, and property safety, commonly occur in mountain regions. Although many efforts have been made, transport of granular flows consisting of polydisperse grains, which is influenced by multiple factors, is still not well understood. This work focused on the effect of small spherical grains on the movement of large stones in granular flows of different grain compositions (quartz gravel, glass bead and angular stone), through experimentally measuring mass frequency distributions of granular materials deposited on flat surface. Three characteristic deposition distances (X₂₀, X₅₀ and X₈₀) and one extreme mobility probability (P_s) were extracted from cumulative frequency distributions. It reveals that, in most of cases, the inclusion of glass beads reduced X₂₀, X₅₀, and X₈₀ but increased P_s for total mass. For angular stone mass, the inclusion of glass beads increased the occurrence frequency of that X₂₀, X₅₀ and X₈₀ increase, apart from increasing P_s. These results indicated small spherical grains could effectively enhance the extreme mobility of large angular stones in mixtures. We hope these results could be helpful for improving our understanding of the transport of geophysical mass flow as well as the grain segregation in different natural environment.