Numerical investigation on non-spherical effects in immersed granular collapse

Abstract

The collapse of immersed granular columns serves as a proxy for submarine landslides, yet natural sediments are rarely the ideal spheres typically assumed in models. To elucidate the poorly understood influence of particle geometry on immersed granular collapse dynamics, this study employs a coupled computational fluid dynamics and discrete element method framework explicitly accounting for non-spherical characteristics. Using the aspect ratio to parameterize particle shape, we analyze the collapse and transport processes of granular columns composed of particles with varying aspect ratios in a fluid environment by digging into the evolution of collapse morphology, particle contact characteristics, energy budgets, and excess pore-fluid pressure responses. This study reveals that increasing particle aspect ratio (i.e., more elongated particles) enhances geometric interlocking effects among particles. This enhanced interlocking constrains both translational and rotational movements, thereby reducing the kinetic energy and energy dissipation of the immersed granular column. Consequently, a greater proportion of energy is retained as potential energy within the deposit, ultimately manifesting as decreased front propagation velocity and reduced final runout distance. Furthermore, variations in the particle aspect ratio influence the dilatancy–contractancy behavior of the granular column, resulting in diminished excess pore-fluid pressure fluctuations with increasing particle aspect ratio. The study also demonstrates that the final runout distance is proportionally correlated with the front kinetic energy, and this relationship remains independent of the particle aspect ratio. These findings advance our understanding of submarine landslide dynamics and provide a theoretical foundation for risk assessment and mitigation of marine geohazards.