Effect of basal friction on granular column collapse

The collapse behaviour of granular materials is influenced by many factors, such as aspect ratio and inter-particle friction. However, the specific impact of basal to grain friction on column collapse remains poorly understood. In this study, we systematically analyse the effect of basal friction on gravity-driven granular column collapse using a validated smoothed particle hydrodynamics (SPH) model. The results show that such the basal friction coefficient does influence deposit geometry, deposit morphology, and energy conversion. To predict the run-out distance, we propose a modified formula that incorporates the basal friction coefficient, considering two extreme cases, i.e., μ = 0 and + ∞. The basal friction also exerts an influence on the final height, with higher friction coefficients resulting in greater final heights. As the friction coefficient increases, the aspect ratio corresponding to the maximum final height also increase. However, we observe a convergence of the effect of basal friction on the final height when μ > 0.5. Furthermore, the competition mechanism between the initial column aspect ratio and basal friction coefficient reveals two transition zones between the three main deposit regimes (regime I, regime II, and regime III). This suggests that the deposit regime can be influenced by basal friction. Additionally, an analysis of energy conversion supports many of the conclusions provided in the text and exhibits the interplay between pressure gradient and base friction. Our findings show the clear influence of basal friction on the collapse behaviour of granular materials and therefore should be carefully considered in future studies.

Graphical Abstract