Size and contact effects in two-dimensional granular column collapse

Gravity-driven granular flows, including debris flows and landslides, represent significant hazards to society. A clear understanding of the relationship between granular column collapse and controlling factors, such as initial geometry and basal conditions, is therefore critical for engineering mitigation. This study examines the collapse of granular columns within varied particle sizes, initial widths, and basal boundary conditions. Key parameters, such as kinematic velocity, collapse acceleration, motion duration, and final deposit morphology, are systematically analyzed. The results highlight the influence of column dimensions and basal friction on collapse dynamics: in dimensionless terms, the size effect is negligible, while basal friction predominantly influences the late stage of collapse, with limited impact during the initial and intermediate phases. Furthermore, in the functional relationships linking runout distance or deposit height to the initial aspect ratio, variations in basal conditions alter only the coefficients, leaving the exponents unchanged. Notably, these exponents also remain invariant with changes in particle size.